diff --git a/Notebooks/SpVec.ipynb b/Notebooks/SpVec.ipynb
index 3e0623c..29df2ae 100644
--- a/Notebooks/SpVec.ipynb
+++ b/Notebooks/SpVec.ipynb
@@ -3,9 +3,7 @@
   {
    "cell_type": "code",
    "execution_count": 1,
-   "metadata": {
-    "collapsed": true
-   },
+   "metadata": {},
    "outputs": [
     {
      "name": "stdout",
@@ -149,7 +147,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 32,
    "metadata": {},
    "outputs": [
     {
@@ -158,7 +156,7 @@
        "val pp : Format.formatter -> t -> unit = <fun>\n"
       ]
      },
-     "execution_count": 3,
+     "execution_count": 32,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -167,12 +165,21 @@
     "let pp ppf t =\n",
     "  let pp_data ppf t =\n",
     "    for i=1 to t.nnz do\n",
-    "      Format.fprintf ppf \"@[(%d,@ %f)@]@;\" t.indices.{i} t.values.{i}\n",
+    "      Format.fprintf ppf \"@[(%d,@ %g)@]@;\" t.indices.{i} t.values.{i}\n",
     "    done\n",
     "  in\n",
     "  Format.fprintf ppf \"@[{@[dim:@ %d@]@;@[%a@]}@]\" t.dim pp_data t"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": 33,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "#install_printer pp"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
@@ -180,55 +187,6 @@
     "# Creators"
    ]
   },
-  {
-   "cell_type": "code",
-   "execution_count": 4,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "val of_vec : ?threshold:float -> Lacaml.D.vec -> t = <fun>\n"
-      ]
-     },
-     "execution_count": 4,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
-   "source": [
-    "let of_vec ?(threshold=0.) v =\n",
-    "  let dim = L.Vec.dim v in\n",
-    "  let buffer_idx = Bigarray.(Array1.create int     fortran_layout) dim in\n",
-    "  let buffer_val = Bigarray.(Array1.create float64 fortran_layout) dim in\n",
-    "  let check = \n",
-    "    if threshold = 0. then\n",
-    "      fun x -> x <> 0.\n",
-    "    else\n",
-    "      fun x -> (abs_float x) > 0.\n",
-    "  in\n",
-    "  let rec aux k i =\n",
-    "    if i > dim then\n",
-    "      k-1\n",
-    "    else if check v.{i} then\n",
-    "      ( buffer_idx.{k} <- i ;\n",
-    "        buffer_val.{k} <- v.{i} ;\n",
-    "        aux (k+1) (i+1)\n",
-    "      )\n",
-    "    else\n",
-    "      aux k (i+1)\n",
-    "  in\n",
-    "  let nnz = aux 1 1 in\n",
-    "  let indices = Bigarray.(Array1.create int fortran_layout) nnz in\n",
-    "  let values  = L.Vec.create nnz in\n",
-    "  for i=1 to nnz do\n",
-    "    indices.{i} <- buffer_idx.{i};\n",
-    "    values.{i} <- buffer_val.{i};\n",
-    "  done ;\n",
-    "  { dim ; nnz ; indices ; values }\n",
-    "\n"
-   ]
-  },
   {
    "cell_type": "code",
    "execution_count": 5,
@@ -256,7 +214,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 77,
+   "execution_count": 6,
    "metadata": {},
    "outputs": [
     {
@@ -265,17 +223,7 @@
        "val of_vec : ?threshold:float -> Lacaml.D.vec -> t = <fun>\n"
       ]
      },
-     "execution_count": 77,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "val of_array : ?threshold:float -> float array -> t = <fun>\n"
-      ]
-     },
-     "execution_count": 77,
+     "execution_count": 6,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -309,9 +257,26 @@
     "    indices.{i} <- buffer_idx.{i};\n",
     "    values.{i} <- buffer_val.{i};\n",
     "  done ;\n",
-    "  { dim ; nnz ; indices ; values }\n",
-    "\n",
-    "\n",
+    "  { dim ; nnz ; indices ; values }"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val of_array : ?threshold:float -> float array -> t = <fun>\n"
+      ]
+     },
+     "execution_count": 7,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
     "let of_array ?(threshold=0.) a =\n",
     "  L.Vec.of_array a\n",
     "  |> of_vec ~threshold "
@@ -319,7 +284,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 78,
+   "execution_count": 8,
    "metadata": {},
    "outputs": [
     {
@@ -328,7 +293,7 @@
        "val copy : t -> t = <fun>\n"
       ]
      },
-     "execution_count": 78,
+     "execution_count": 8,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -345,59 +310,117 @@
     "    indices ; values }"
    ]
   },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "## Test"
-   ]
-  },
   {
    "cell_type": "code",
-   "execution_count": 79,
+   "execution_count": 37,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "val x : t =\n",
-       "  {dim = 10; nnz = 0; indices = <abstr>;\n",
-       "   values =\n",
-       "             R1          R2 R3             R30         R31         R32\n",
-       "    6.9331E-310 6.9331E-310  0 ... 6.9331E-310 6.9331E-310 6.9331E-310}\n"
+       "val map : ?threshold:float -> (float -> float) -> t -> t = <fun>\n"
       ]
      },
-     "execution_count": 79,
+     "execution_count": 37,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let map ?(threshold=0.) f t =\n",
+    "  let indices = \n",
+    "    Bigarray.(Array1.create int fortran_layout) t.nnz\n",
+    "  in\n",
+    "  let check =\n",
+    "    if threshold = 0. then\n",
+    "      fun x -> x <> 0.\n",
+    "    else\n",
+    "      fun x -> abs_float x > threshold\n",
+    "  in\n",
+    "  let values = L.Vec.create t.nnz in\n",
+    "  let nnz = ref 0 in\n",
+    "  for i=1 to t.nnz do\n",
+    "    let w = f t.values.{i} in\n",
+    "    if check w then (\n",
+    "      incr nnz;\n",
+    "      values.{!nnz} <- w ;\n",
+    "      indices.{!nnz} <- t.indices.{i}\n",
+    "    )\n",
+    "  done;\n",
+    "  { dim = t.dim ;\n",
+    "    nnz = !nnz ;\n",
+    "    indices ; values }"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Test"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 38,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val x : t = {dim: 10 }\n"
+      ]
+     },
+     "execution_count": 38,
      "metadata": {},
      "output_type": "execute_result"
     },
     {
      "data": {
       "text/plain": [
-       "val dense_a : t =\n",
-       "  {dim = 9; nnz = 5; indices = <abstr>;\n",
-       "   values = R1 R2  R3    R4 R5\n",
-       "             1 -2 0.5 1E-08  3}\n"
+       "val dense_a : Lacaml.D.vec = R1 R2 R3     R7 R8 R9\n",
+       "                              1 -2  0 ...  0  3  0\n"
       ]
      },
-     "execution_count": 79,
+     "execution_count": 38,
      "metadata": {},
      "output_type": "execute_result"
     },
     {
-     "ename": "error",
-     "evalue": "compile_error",
-     "output_type": "error",
-     "traceback": [
-      "\u001b[32mFile \"[79]\", line 6, characters 22-29:\n\u001b[31mError: This expression has type t but an expression was expected of type\n         Lacaml.D.vec =\n           (float, Bigarray.float64_elt, Bigarray.fortran_layout)\n           Bigarray.Array1.t\n\u001b[36m   5: \u001b[30m   \n\u001b[36m   6: \u001b[30mlet sparse_a = of_vec \u001b[4mdense_a\u001b[0m\u001b[30m \n\u001b[36m   7: \u001b[30m\u001b[0m\n"
-     ]
+     "data": {
+      "text/plain": [
+       "val sparse_a : t = {dim: 9 (1, 1) (2, -2) (5, 0.5) (6, 1e-08) (8, 3) }\n"
+      ]
+     },
+     "execution_count": 38,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "- : bool = true\n"
+      ]
+     },
+     "execution_count": 38,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "- : bool = false\n"
+      ]
+     },
+     "execution_count": 38,
+     "metadata": {},
+     "output_type": "execute_result"
     }
    ],
    "source": [
     "let x = make0 10 \n",
     "\n",
     "let dense_a = \n",
-    "   of_array [| 1. ; -2. ; 0. ; 0. ; 0.5 ; 1.e-8 ; 0. ; 3. ; 0. |]\n",
+    "   L.Vec.of_array [| 1. ; -2. ; 0. ; 0. ; 0.5 ; 1.e-8 ; 0. ; 3. ; 0. |]\n",
     "   \n",
     "let sparse_a = of_vec dense_a \n",
     "\n",
@@ -405,17 +428,526 @@
     "    copy sparse_a = sparse_a\n",
     "    \n",
     "let _ =\n",
-    "    copy sparse_a == sparse_a\n",
-    "\n",
-    "let () = \n",
-    "    Format.printf \"@.@[%a@]@.\" pp sparse_a"
+    "    copy sparse_a == sparse_a\n"
    ]
   },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# aX + Y\n",
+    "# Accessors"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 39,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val dim : t -> int = <fun>\n"
+      ]
+     },
+     "execution_count": 39,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val nnz : t -> int = <fun>\n"
+      ]
+     },
+     "execution_count": 39,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val indices :\n",
+       "  t -> (int, Bigarray.int_elt, Bigarray.fortran_layout) Bigarray.Array1.t =\n",
+       "  <fun>\n"
+      ]
+     },
+     "execution_count": 39,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val values : t -> L.Vec.t = <fun>\n"
+      ]
+     },
+     "execution_count": 39,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val density : t -> float = <fun>\n"
+      ]
+     },
+     "execution_count": 39,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let dim t = t.dim\n",
+    "let nnz t = t.nnz\n",
+    "let indices t = t.indices\n",
+    "let values  t = t.values\n",
+    "let density t = float_of_int t.nnz /. float_of_int t.dim"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 40,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val get : t -> int -> float = <fun>\n"
+      ]
+     },
+     "execution_count": 40,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let get t i =\n",
+    "  if i < 1 || i > dim t then invalid_arg \"index out of bounds\";\n",
+    "                                                                                              \n",
+    "  let rec binary_search index value low high =\n",
+    "    if high = low then\n",
+    "      if index.{low} = value then\n",
+    "        low\n",
+    "      else\n",
+    "        raise Not_found\n",
+    "    else let mid = (low + high) / 2 in\n",
+    "      if index.{mid} > value then\n",
+    "        binary_search index value low (mid - 1)\n",
+    "      else if index.{mid} < value then\n",
+    "        binary_search index value (mid + 1) high\n",
+    "      else\n",
+    "        mid\n",
+    "  in\n",
+    "  try\n",
+    "    let k = \n",
+    "      let id = indices t in\n",
+    "      binary_search id i id.{1} (nnz t)\n",
+    "    in\n",
+    "    t.values.{k}\n",
+    "  with Not_found -> 0."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 41,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val iter : (int -> float -> 'a) -> t -> unit = <fun>\n"
+      ]
+     },
+     "execution_count": 41,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let iter f t =\n",
+    "  for k=1 to nnz t do\n",
+    "    f t.indices.{k} t.values.{k}\n",
+    "  done"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Test "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 42,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "- : bool = true\n"
+      ]
+     },
+     "execution_count": 42,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "1 1.000000\n",
+      "2 -2.000000\n",
+      "5 0.500000\n",
+      "6 0.000000\n",
+      "8 3.000000\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "- : unit = ()\n"
+      ]
+     },
+     "execution_count": 42,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "dense_a = L.Vec.init (dim sparse_a) (get sparse_a);;\n",
+    "iter (fun i v -> Printf.printf \"%d %f\\n%!\" i v) sparse_a;;"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Converters"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 43,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val to_assoc_list : t -> (int * float) list = <fun>\n"
+      ]
+     },
+     "execution_count": 43,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val to_vec : t -> Lacaml.D.vec = <fun>\n"
+      ]
+     },
+     "execution_count": 43,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let to_assoc_list t = \n",
+    "  let rec aux k accu =\n",
+    "    if k = 0 then\n",
+    "      accu\n",
+    "    else\n",
+    "      aux (k-1) ( (t.indices.{k}, t.values.{k})::accu )\n",
+    "  in\n",
+    "  aux (nnz t) []\n",
+    "  \n",
+    "  \n",
+    "let to_vec t =\n",
+    "  let result = L.Vec.make0 (dim t) in\n",
+    "  iter (fun k v -> result.{k} <- v) t;\n",
+    "  result\n",
+    "  "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Test"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 44,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "- : (int * float) list = [(1, 1.); (2, -2.); (5, 0.5); (6, 1e-08); (8, 3.)]\n"
+      ]
+     },
+     "execution_count": 44,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "- : bool = true\n"
+      ]
+     },
+     "execution_count": 44,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "to_assoc_list sparse_a;;\n",
+    "to_vec sparse_a = dense_a;;"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Operations"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## One-vector operations"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 45,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val immutable : (t -> 'a) -> t -> t = <fun>\n"
+      ]
+     },
+     "execution_count": 45,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val scale_mut : float -> t -> unit = <fun>\n"
+      ]
+     },
+     "execution_count": 45,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val scale : float -> t -> t = <fun>\n"
+      ]
+     },
+     "execution_count": 45,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val neg : t -> t = <fun>\n"
+      ]
+     },
+     "execution_count": 45,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val norm : t -> float = <fun>\n"
+      ]
+     },
+     "execution_count": 45,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let immutable f t =\n",
+    "  let result = copy t in\n",
+    "  f result;\n",
+    "  result\n",
+    "  \n",
+    "let scale_mut x t = \n",
+    "  L.scal x t.values \n",
+    "\n",
+    "let scale x = immutable @@ scale_mut x\n",
+    "  \n",
+    "let neg t =\n",
+    "  { t with values = L.Vec.neg t.values }\n",
+    "  \n",
+    "let norm t =\n",
+    "  L.nrm2 t.values\n",
+    "  "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Test"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 47,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val sparse_b : t = {dim: 9 (1, 1) (2, -2) (5, 0.5) (6, 1e-08) (8, 3) }\n"
+      ]
+     },
+     "execution_count": 47,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "- : unit = ()\n"
+      ]
+     },
+     "execution_count": 47,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "- : bool = true\n"
+      ]
+     },
+     "execution_count": 47,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val dense_b : L.vec = R1 R2 R3     R7 R8 R9\n",
+       "                       1 -2  0 ...  0  3  0\n"
+      ]
+     },
+     "execution_count": 47,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "- : unit = ()\n"
+      ]
+     },
+     "execution_count": 47,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val sparse_c : t = {dim: 9 (1, 0.5) (2, -1) (5, 0.25) (6, 5e-09) (8, 1.5) }\n"
+      ]
+     },
+     "execution_count": 47,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "- : bool = true\n"
+      ]
+     },
+     "execution_count": 47,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "- : bool = true\n"
+      ]
+     },
+     "execution_count": 47,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let sparse_b = copy sparse_a;;\n",
+    "scale_mut 0.5 sparse_b;;\n",
+    "\n",
+    "equal sparse_b @@ map (fun x -> x *. 0.5) sparse_a;;\n",
+    "\n",
+    "\n",
+    "let dense_b = L.copy dense_a;;\n",
+    "L.scal 0.5 dense_b;;\n",
+    "\n",
+    "let sparse_c = scale 0.5 sparse_a;;\n",
+    "\n",
+    "equal sparse_b sparse_c;;\n",
+    "    \n",
+    "let _ =\n",
+    "    let n1 = neg sparse_a in\n",
+    "    neg n1 = sparse_a"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Two-vector operations"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 19,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val equal : t -> t -> bool = <fun>\n"
+      ]
+     },
+     "execution_count": 19,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let equal x y =\n",
+    "  (x.nnz + y.nnz = 0) || (\n",
+    "  (x.dim = y.dim) &&\n",
+    "  (x.nnz  = y.nnz) &&\n",
+    "  Bigarray.Array1.(sub x.indices 1 x.nnz = sub y.indices 1 y.nnz) &&\n",
+    "  (Array.sub (L.Vec.to_array x.values) 0 (x.nnz-1) = Array.sub (L.Vec.to_array y.values) 0 (y.nnz-1) )\n",
+    "  )"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## aX + Y\n",
     "\n",
     "Run along all the entries of `X` and `Y` simultaneously with indices `k` and `l`. `m` is the index of the new array.\n",
     "\n",
@@ -428,7 +960,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 105,
+   "execution_count": 20,
    "metadata": {},
    "outputs": [
     {
@@ -437,7 +969,7 @@
        "val axpy : ?threshold:float -> ?alpha:float -> t -> t -> t = <fun>\n"
       ]
      },
-     "execution_count": 105,
+     "execution_count": 20,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -452,7 +984,7 @@
     "    if threshold = 0. then\n",
     "      fun x -> x <> 0.\n",
     "    else\n",
-    "      fun x -> abs_float x > 0.\n",
+    "      fun x -> abs_float x > threshold\n",
     "    in\n",
     "    \n",
     "  let f = (* if a=1 in ax+y, then do x+y. If a=0 then do y *)\n",
@@ -477,25 +1009,25 @@
     "          let w = f x.values.{k} 0. in\n",
     "          if check w then (\n",
     "              new_indices.{m} <- x.indices.{k};\n",
-    "              new_values.{m} <- w\n",
-    "          );\n",
-    "          (aux [@tailcall]) (k+1) l (m+1)\n",
+    "              new_values.{m} <- w ;\n",
+    "              (aux [@tailcall]) (k+1) l (m+1)\n",
+    "          ) else (aux [@tailcall]) (k+1) l m\n",
     "        )\n",
     "        else if x.indices.{k} > y.indices.{l} then (\n",
     "          let w = y.values.{l} in\n",
     "          if check w then (\n",
     "              new_indices.{m} <- y.indices.{l};\n",
-    "              new_values.{m} <- w\n",
-    "          );\n",
-    "          (aux [@tailcall]) k (l+1) (m+1)\n",
+    "              new_values.{m} <- w;\n",
+    "              (aux [@tailcall]) k (l+1) (m+1)\n",
+    "          ) else (aux [@tailcall]) k (l+1) m\n",
     "        )\n",
     "        else (\n",
     "          let w = f x.values.{k} y.values.{l} in\n",
     "          if check w then (\n",
     "              new_indices.{m} <- x.indices.{k};\n",
-    "              new_values.{m} <- w\n",
-    "          );\n",
-    "          (aux [@tailcall]) (k+1) (l+1) (m+1)\n",
+    "              new_values.{m} <- w;\n",
+    "              (aux [@tailcall]) (k+1) (l+1) (m+1)\n",
+    "          ) else (aux [@tailcall]) (k+1) (l+1) m\n",
     "        )\n",
     "      end\n",
     "    | false, true  -> (* Array x is done running *)\n",
@@ -531,19 +1063,50 @@
     "    "
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": 21,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val add : ?threshold:float -> t -> t -> t = <fun>\n"
+      ]
+     },
+     "execution_count": 21,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val sub : ?threshold:float -> t -> t -> t = <fun>\n"
+      ]
+     },
+     "execution_count": 21,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let add ?(threshold=0.) x y = axpy ~threshold ~alpha:1. x y\n",
+    "\n",
+    "let sub ?(threshold=0.) x y = axpy ~threshold ~alpha:(-1.) y x\n",
+    "    "
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Test"
+    "### Test"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 108,
-   "metadata": {
-    "collapsed": true
-   },
+   "execution_count": 22,
+   "metadata": {},
    "outputs": [
     {
      "data": {
@@ -552,7 +1115,7 @@
        "                          1  2  0 ... -0.001  0   0\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
@@ -563,33 +1126,27 @@
        "                          0  1  2 ...  0 -0.001   2\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
     {
      "data": {
       "text/plain": [
-       "val m_As : t =\n",
-       "  {dim = 10; nnz = 5; indices = <abstr>;\n",
-       "   values = R1 R2   R3 R4     R5\n",
-       "             1  2 0.01 -2 -0.001}\n"
+       "val m_As : t = {dim: 10 (1, 1 (2, 2 (5, 0.01 (6, -2 (8, -0.001 }\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
     {
      "data": {
       "text/plain": [
-       "val m_Bs : t =\n",
-       "  {dim = 10; nnz = 6; indices = <abstr>;\n",
-       "   values = R1 R2   R3 R4     R5 R6\n",
-       "             1  2 0.01 -2 -0.001  2}\n"
+       "val m_Bs : t = {dim: 10 (2, 1 (3, 2 (6, 0.01 (7, -2 (9, -0.001 (10, 2 }\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
@@ -600,7 +1157,7 @@
        "                   0  1  2 ...  0 -0.001   2\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
@@ -610,7 +1167,7 @@
        "- : unit = ()\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
@@ -621,7 +1178,7 @@
        "             2  5  2 ... -0.002 -0.001   2\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
@@ -632,7 +1189,7 @@
        "                   1  2  0 ... -0.001  0   0\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
@@ -642,7 +1199,7 @@
        "- : unit = ()\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
@@ -653,7 +1210,7 @@
        "             1  4  4 ... -0.001 -0.002   4\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
@@ -661,23 +1218,21 @@
      "data": {
       "text/plain": [
        "val m_Cs : t =\n",
-       "  {dim = 10; nnz = 9; indices = <abstr>;\n",
-       "   values =\n",
-       "    R1 R2 R3     R9         R10          R11\n",
-       "     2  5  2 ...  2 1.04136E-71 8.95166E+271}\n"
+       "  {dim: 10\n",
+       "  (1, 2 (2, 5 (3, 2 (5, 0.02 (6, -3.99 (7, -2 (8, -0.002 (9, -0.001 (10, 2 }\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
     {
      "data": {
       "text/plain": [
-       "- : bool = false\n"
+       "- : bool = true\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
@@ -685,75 +1240,21 @@
      "data": {
       "text/plain": [
        "val m_Ds : t =\n",
-       "  {dim = 10; nnz = 9; indices = <abstr>;\n",
-       "   values =\n",
-       "    R1 R2 R3     R9         R10         R11\n",
-       "     1  4  4 ...  4 6.82475E-38 8.26993E-72}\n"
+       "  {dim: 10\n",
+       "  (1, 1 (2, 4 (3, 4 (5, 0.01 (6, -1.98 (7, -4 (8, -0.001 (9, -0.002 (10, 4 }\n"
       ]
      },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     },
     {
      "data": {
       "text/plain": [
-       "- : bool = false\n"
+       "- : bool = true\n"
       ]
      },
-     "execution_count": 108,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "1 2.000000 2.000000\n",
-      "2 5.000000 5.000000\n",
-      "3 2.000000 2.000000\n",
-      "4 0.000000 0.000000\n",
-      "5 0.020000 0.020000\n",
-      "6 -3.990000 -3.990000\n",
-      "7 -2.000000 -2.000000\n",
-      "8 -0.002000 -0.002000\n",
-      "9 -0.001000 -0.001000\n",
-      "10 2.000000 2.000000\n"
-     ]
-    },
-    {
-     "data": {
-      "text/plain": [
-       "- : unit = ()\n"
-      ]
-     },
-     "execution_count": 108,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "1 1.000000 1.000000\n",
-      "2 4.000000 4.000000\n",
-      "3 4.000000 4.000000\n",
-      "4 0.000000 0.000000\n",
-      "5 0.010000 0.010000\n",
-      "6 -1.980000 -1.980000\n",
-      "7 -4.000000 -4.000000\n",
-      "8 -0.001000 -0.001000\n",
-      "9 -0.002000 -0.002000\n",
-      "10 4.000000 4.000000\n"
-     ]
-    },
-    {
-     "data": {
-      "text/plain": [
-       "- : unit = ()\n"
-      ]
-     },
-     "execution_count": 108,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -776,361 +1277,56 @@
     "let m_Cs = axpy ~alpha:2. m_As m_Bs\n",
     "\n",
     "\n",
-    "let _ =  of_vec m_C = m_Cs;;\n",
+    "let _ =  equal (of_vec m_C) m_Cs;;\n",
     "\n",
     "let m_Ds = axpy ~alpha:2. m_Bs m_As\n",
     "\n",
-    "let _ = of_vec m_D = m_Ds;;\n",
+    "let _ = equal (of_vec m_D) m_Ds;;\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Dot product"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 23,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val dot : t -> t -> float = <fun>\n"
+      ]
+     },
+     "execution_count": 23,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let dot x y =\n",
     "\n",
-    "L.Vec.iteri (fun i x -> Format.printf \"%d %f %f\\n%!\" i x (get m_Cs i)) m_C;;\n",
-    "L.Vec.iteri (fun i x -> Format.printf \"%d %f %f\\n%!\" i x (get m_Ds i)) m_D;;\n"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "# Accessors"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 24,
-   "metadata": {
-    "collapsed": true
-   },
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "val dim : t -> int = <fun>\n"
-      ]
-     },
-     "execution_count": 24,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "val nnz : t -> int = <fun>\n"
-      ]
-     },
-     "execution_count": 24,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "val indices :\n",
-       "  t -> (int, Bigarray.int_elt, Bigarray.fortran_layout) Bigarray.Array1.t =\n",
-       "  <fun>\n"
-      ]
-     },
-     "execution_count": 24,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "val values : t -> L.Vec.t = <fun>\n"
-      ]
-     },
-     "execution_count": 24,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
-   "source": [
-    "let dim t = t.dim\n",
-    "let nnz t = t.nnz\n",
-    "let indices t = t.indices\n",
-    "let values  t = t.values"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 25,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "val get : t -> int -> float = <fun>\n"
-      ]
-     },
-     "execution_count": 25,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
-   "source": [
-    "let get t i =\n",
-    "  if i < 1 || i > dim t then invalid_arg \"index out of bounds\";\n",
-    "                                                                                              \n",
-    "  let rec binary_search index value low high =\n",
-    "    if high = low then\n",
-    "      if index.{low} = value then\n",
-    "        low\n",
-    "      else\n",
-    "        raise Not_found\n",
-    "    else let mid = (low + high) / 2 in\n",
-    "      if index.{mid} > value then\n",
-    "        binary_search index value low (mid - 1)\n",
-    "      else if index.{mid} < value then\n",
-    "        binary_search index value (mid + 1) high\n",
-    "      else\n",
-    "        mid\n",
-    "  in\n",
-    "  try\n",
-    "    let k = \n",
-    "      let id = indices t in\n",
-    "      binary_search id i id.{1} (nnz t)\n",
-    "    in\n",
-    "    t.values.{k}\n",
-    "  with Not_found -> 0."
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 26,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "val iter : (int -> float -> 'a) -> t -> unit = <fun>\n"
-      ]
-     },
-     "execution_count": 26,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
-   "source": [
-    "let iter f t =\n",
-    "  for k=1 to nnz t do\n",
-    "    f t.indices.{k} t.values.{k}\n",
-    "  done"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "## Test "
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 28,
-   "metadata": {
-    "collapsed": true
-   },
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "- : bool = true\n"
-      ]
-     },
-     "execution_count": 28,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "1 1.000000\n",
-      "2 -2.000000\n",
-      "5 0.500000\n",
-      "6 0.000000\n",
-      "8 3.000000\n"
-     ]
-    },
-    {
-     "data": {
-      "text/plain": [
-       "- : unit = ()\n"
-      ]
-     },
-     "execution_count": 28,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
-   "source": [
-    "dense_a = L.Vec.init (dim sparse_a) (get sparse_a);;\n",
-    "iter (fun i v -> Printf.printf \"%d %f\\n%!\" i v) sparse_a;;"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "# Converters"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 30,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "val to_assoc_list : t -> (int * float) list = <fun>\n"
-      ]
-     },
-     "execution_count": 30,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "val to_vec : t -> Lacaml.D.vec = <fun>\n"
-      ]
-     },
-     "execution_count": 30,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
-   "source": [
-    "let to_assoc_list t = \n",
-    "  let rec aux k accu =\n",
-    "    if k = 0 then\n",
-    "      accu\n",
+    "  let rec aux accu k l =\n",
+    "    if k <= x.nnz && l <= y.nnz then\n",
+    "      begin\n",
+    "        if x.indices.{k} < y.indices.{l} then \n",
+    "          (aux [@tailcall]) accu (k+1) l\n",
+    "        else if x.indices.{k} > y.indices.{l} then (\n",
+    "          (aux [@tailcall]) accu k (l+1)\n",
+    "        )\n",
+    "        else (\n",
+    "          (aux [@tailcall]) (accu +. x.values.{k} *. y.values.{l}) (k+1) (l+1)\n",
+    "        )\n",
+    "      end\n",
     "    else\n",
-    "      aux (k-1) ( (t.indices.{k}, t.values.{k})::accu )\n",
+    "      accu\n",
     "  in\n",
-    "  aux (nnz t) []\n",
-    "  \n",
-    "  \n",
-    "let to_vec t =\n",
-    "  let result = L.Vec.make0 (dim t) in\n",
-    "  iter (fun k v -> result.{k} <- v) t;\n",
-    "  result"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "## Test"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 31,
-   "metadata": {
-    "collapsed": true
-   },
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "- : (int * float) list = [(1, 1.); (2, -2.); (5, 0.5); (6, 1e-08); (8, 3.)]\n"
-      ]
-     },
-     "execution_count": 31,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "- : bool = true\n"
-      ]
-     },
-     "execution_count": 31,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
-   "source": [
-    "to_assoc_list sparse_a;;\n",
-    "to_vec sparse_a = dense_a;;"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "# Operations"
-   ]
-  },
-  {
-   "cell_type": "markdown",
-   "metadata": {},
-   "source": [
-    "## One-vector operations"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": 64,
-   "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "val immutable : (t -> 'a) -> t -> t = <fun>\n"
-      ]
-     },
-     "execution_count": 64,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "val scale_mut : float -> t -> unit = <fun>\n"
-      ]
-     },
-     "execution_count": 64,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "val scale : float -> t -> t = <fun>\n"
-      ]
-     },
-     "execution_count": 64,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "val neg : t -> t = <fun>\n"
-      ]
-     },
-     "execution_count": 64,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
-   "source": [
-    "let immutable f t =\n",
-    "  let result = copy t in\n",
-    "  f result;\n",
-    "  result\n",
-    "  \n",
-    "let scale_mut x t = \n",
-    "  L.scal x t.values \n",
-    "\n",
-    "let scale x = immutable @@ scale_mut x\n",
-    "  \n",
-    "let neg t =\n",
-    "  { t with values = L.Vec.neg t.values }\n",
-    "  "
+    "  aux 0. 1 1\n"
    ]
   },
   {
@@ -1142,148 +1338,415 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 67,
+   "execution_count": 24,
    "metadata": {},
    "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "val sparse_b : t =\n",
-       "  {dim = 9; nnz = 5; indices = <abstr>;\n",
-       "   values = R1 R2  R3    R4 R5\n",
-       "             1 -2 0.5 1E-08  3}\n"
-      ]
-     },
-     "execution_count": 67,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "- : unit = ()\n"
-      ]
-     },
-     "execution_count": 67,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "data": {
-      "text/plain": [
-       "val sparse_c : t =\n",
-       "  {dim = 9; nnz = 5; indices = <abstr>;\n",
-       "   values =  R1 R2   R3    R4  R5\n",
-       "            0.5 -1 0.25 5E-09 1.5}\n"
-      ]
-     },
-     "execution_count": 67,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "{dim: 9\n",
-      "(1, 1.000000) (2, -2.000000) (5, 0.500000) (6, 0.000000) (8, 3.000000) }\n"
-     ]
-    },
-    {
-     "data": {
-      "text/plain": [
-       "- : unit = ()\n"
-      ]
-     },
-     "execution_count": 67,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "{dim: 9\n",
-      "(1, 0.500000) (2, -1.000000) (5, 0.250000) (6, 0.000000) (8, 1.500000) }\n"
-     ]
-    },
-    {
-     "data": {
-      "text/plain": [
-       "- : unit = ()\n"
-      ]
-     },
-     "execution_count": 67,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "{dim: 9\n",
-      "(1, 0.500000) (2, -1.000000) (5, 0.250000) (6, 0.000000) (8, 1.500000) }\n"
-     ]
-    },
-    {
-     "data": {
-      "text/plain": [
-       "- : unit = ()\n"
-      ]
-     },
-     "execution_count": 67,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "{dim: 9\n",
-      "(1, -1.000000) (2, 2.000000) (5, -0.500000) (6, -0.000000) (8, -3.000000) }\n"
-     ]
-    },
-    {
-     "data": {
-      "text/plain": [
-       "- : unit = ()\n"
-      ]
-     },
-     "execution_count": 67,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
     {
      "data": {
       "text/plain": [
        "- : bool = true\n"
       ]
      },
-     "execution_count": 67,
+     "execution_count": 24,
      "metadata": {},
      "output_type": "execute_result"
     }
    ],
    "source": [
-    "let sparse_b = copy sparse_a;;\n",
-    "scale_mut 0.5 sparse_b;;\n",
-    "let sparse_c = scale 0.5 sparse_a;;\n",
-    "Format.printf \"%a@.\" pp sparse_a;;\n",
-    "Format.printf \"%a@.\" pp sparse_b;;\n",
-    "Format.printf \"%a@.\" pp sparse_c;;\n",
-    "Format.printf \"%a@.\" pp (neg sparse_a);;\n",
-    "    \n",
-    "let _ =\n",
-    "    let n1 = neg sparse_a in\n",
-    "    neg n1 = sparse_a"
+    "dot sparse_a sparse_b = L.dot dense_a dense_b;;"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Tests"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 25,
    "metadata": {},
-   "outputs": [],
-   "source": []
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/home/scemama/qp2/external/opam/default/lib/astring: added to search path\n",
+      "/home/scemama/qp2/external/opam/default/lib/astring/astring.cma: loaded\n",
+      "/home/scemama/qp2/external/opam/default/lib/cmdliner: added to search path\n",
+      "/home/scemama/qp2/external/opam/default/lib/cmdliner/cmdliner.cma: loaded\n",
+      "/home/scemama/qp2/external/opam/default/lib/seq: added to search path\n",
+      "/home/scemama/qp2/external/opam/default/lib/stdlib-shims: added to search path\n",
+      "/home/scemama/qp2/external/opam/default/lib/stdlib-shims/stdlib_shims.cma: loaded\n",
+      "/home/scemama/qp2/external/opam/default/lib/fmt: added to search path\n",
+      "/home/scemama/qp2/external/opam/default/lib/fmt/fmt.cma: loaded\n",
+      "/home/scemama/qp2/external/opam/default/lib/fmt/fmt_cli.cma: loaded\n",
+      "/home/scemama/qp2/external/opam/default/lib/fmt/fmt_tty.cma: loaded\n",
+      "/home/scemama/qp2/external/opam/default/lib/alcotest: added to search path\n",
+      "/home/scemama/qp2/external/opam/default/lib/alcotest/alcotest.cma: loaded\n"
+     ]
+    }
+   ],
+   "source": [
+    "#require \"alcotest\";;"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 26,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val x1 : Lacaml.D.vec =\n",
+       "        R1 R2 R3     R98      R99 R100\n",
+       "  0.852078  0  0 ...   0 0.656419    0\n",
+       "val x2 : Lacaml.D.vec =\n",
+       "         R1       R2 R3           R98 R99   R100\n",
+       "  -0.606197 0.411059  0 ... -0.368989   0 0.9001\n"
+      ]
+     },
+     "execution_count": 26,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val x3 : Lacaml.D.vec =\n",
+       "       R1 R2 R3     R98     R99 R100\n",
+       "  1.70416  0  0 ...   0 1.31284    0\n",
+       "val x4 : Lacaml.D.vec =\n",
+       "        R1       R2 R3           R98      R99   R100\n",
+       "  0.245881 0.411059  0 ... -0.368989 0.656419 0.9001\n",
+       "val x5 : Lacaml.D.vec =\n",
+       "       R1        R2 R3          R98      R99    R100\n",
+       "  1.45827 -0.411059  0 ... 0.368989 0.656419 -0.9001\n",
+       "val x6 : L.vec =\n",
+       "       R1       R2 R3           R98     R99   R100\n",
+       "  1.95004 0.411059  0 ... -0.368989 1.96926 0.9001\n"
+      ]
+     },
+     "execution_count": 26,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val v1 : Lacaml.D.vec =\n",
+       "        R1 R2 R3     R98      R99 R100\n",
+       "  0.852078  0  0 ...   0 0.656419    0\n",
+       "val v2 : Lacaml.D.vec =\n",
+       "         R1       R2 R3           R98 R99   R100\n",
+       "  -0.606197 0.411059  0 ... -0.368989   0 0.9001\n",
+       "val v3 : Lacaml.D.vec =\n",
+       "       R1 R2 R3     R98     R99 R100\n",
+       "  1.70416  0  0 ...   0 1.31284    0\n",
+       "val v4 : Lacaml.D.vec =\n",
+       "        R1       R2 R3           R98      R99   R100\n",
+       "  0.245881 0.411059  0 ... -0.368989 0.656419 0.9001\n",
+       "val v5 : Lacaml.D.vec =\n",
+       "       R1        R2 R3          R98      R99    R100\n",
+       "  1.45827 -0.411059  0 ... 0.368989 0.656419 -0.9001\n",
+       "val v6 : L.vec =\n",
+       "       R1       R2 R3           R98     R99   R100\n",
+       "  1.95004 0.411059  0 ... -0.368989 1.96926 0.9001\n"
+      ]
+     },
+     "execution_count": 26,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val v1_s : t =\n",
+       "  {dim: 100\n",
+       "  (1, 0.852078 (4, 0.733763 (7, -0.818022 (10, -0.692304 (11, -0.980468\n",
+       "  (15, 0.974355 (16, -0.665109 (24, 0.889086 (27, 0.736393 (30, -0.843748\n",
+       "  (31, -0.750514 (34, 0.778919 (38, -0.790597 (40, 0.720996 (41, 0.978861\n",
+       "  (42, -0.679388 (43, -0.853596 (46, 0.977185 (47, -0.811648 (49, -0.702925\n",
+       "  (50, 0.89789 (54, -0.675687 (56, 0.752085 (57, -0.626277 (66, 0.664662\n",
+       "  (67, 0.855765 (69, 0.673572 (71, -0.764248 (72, 0.61481 (73, -0.849851\n",
+       "  (74, -0.983965 (84, -0.764701 (87, -0.834976 (92, -0.851806 (94, 0.696202\n",
+       "  (95, 0.844479 (99, 0.656419 }\n",
+       "val v2_s : t =\n",
+       "  {dim: 100\n",
+       "  (1, -0.606197 (2, 0.411059 (4, 0.329122 (5, -0.740514 (7, 0.387312\n",
+       "  (8, 0.977894 (9, -0.43281 (11, -0.971917 (15, -0.471397 (16, 0.863036\n",
+       "  (17, -0.497091 (19, 0.8659 (20, 0.572763 (21, 0.963705 (23, -0.568959\n",
+       "  (24, 0.643522 (25, 0.697603 (26, -0.706857 (29, -0.874151 (30, 0.559791\n",
+       "  (32, -0.392582 (34, -0.488787 (36, -0.988593 (38, -0.817274 (39, -0.78555\n",
+       "  (42, 0.505945 (43, 0.370838 (44, -0.734224 (45, -0.634506 (46, 0.304503\n",
+       "  (47, -0.330526 (48, -0.800156 (49, -0.570671 (50, -0.514998 (51, -0.47082\n",
+       "  (52, 0.731985 (53, -0.501758 (54, -0.856375 (55, 0.422431 (56, 0.819669\n",
+       "  (57, 0.847078 (58, 0.301306 (59, -0.917181 (60, 0.391153 (61, -0.936169\n",
+       "  (62, 0.855439 (63, 0.730839 (64, 0.763087 (65, 0.777606 (66, 0.945573\n",
+       "  (67, -0.584689 (68, 0.312286 (69, 0.840451 (72, 0.980958 (73, 0.383844\n",
+       "  (77, 0.509676 (79, 0.86618 (80, -0.767171 (82, -0.955884 (83, -0.326832\n",
+       "  (88, 0.846553 (89, -0.578475 (90, -0.522823 (91, 0.802248 (92, 0.975437\n",
+       "  (95, -0.816165 (96, -0.999559 (97, 0.738769 (98, -0.368989 (100, 0.9001 }\n",
+       "val v3_s : t =\n",
+       "  {dim: 100\n",
+       "  (1, 1.70416 (4, 1.46753 (7, -1.63604 (10, -1.38461 (11, -1.96094\n",
+       "  (15, 1.94871 (16, -1.33022 (24, 1.77817 (27, 1.47279 (30, -1.6875\n",
+       "  (31, -1.50103 (34, 1.55784 (38, -1.58119 (40, 1.44199 (41, 1.95772\n",
+       "  (42, -1.35878 (43, -1.70719 (46, 1.95437 (47, -1.6233 (49, -1.40585\n",
+       "  (50, 1.79578 (54, -1.35137 (56, 1.50417 (57, -1.25255 (66, 1.32932\n",
+       "  (67, 1.71153 (69, 1.34714 (71, -1.5285 (72, 1.22962 (73, -1.6997\n",
+       "  (74, -1.96793 (84, -1.5294 (87, -1.66995 (92, -1.70361 (94, 1.3924\n",
+       "  (95, 1.68896 (99, 1.31284 }\n",
+       "val v4_s : t =\n",
+       "  {dim: 100\n",
+       "  (1, 0.245881 (2, 0.411059 (4, 1.06289 (5, -0.740514 (7, -0.43071\n",
+       "  (8, 0.977894 (9, -0.43281 (10, -0.692304 (11, -1.95238 (15, 0.502957\n",
+       "  (16, 0.197927 (17, -0.497091 (19, 0.8659 (20, 0.572763 (21, 0.963705\n",
+       "  (23, -0.568959 (24, 1.53261 (25, 0.697603 (26, -0.706857 (27, 0.736393\n",
+       "  (29, -0.874151 (30, -0.283957 (31, -0.750514 (32, -0.392582 (34, 0.290132\n",
+       "  (36, -0.988593 (38, -1.60787 (39, -0.78555 (40, 0.720996 (41, 0.978861\n",
+       "  (42, -0.173443 (43, -0.482758 (44, -0.734224 (45, -0.634506 (46, 1.28169\n",
+       "  (47, -1.14217 (48, -0.800156 (49, -1.2736 (50, 0.382892 (51, -0.47082\n",
+       "  (52, 0.731985 (53, -0.501758 (54, -1.53206 (55, 0.422431 (56, 1.57175\n",
+       "  (57, 0.220801 (58, 0.301306 (59, -0.917181 (60, 0.391153 (61, -0.936169\n",
+       "  (62, 0.855439 (63, 0.730839 (64, 0.763087 (65, 0.777606 (66, 1.61024\n",
+       "  (67, 0.271076 (68, 0.312286 (69, 1.51402 (71, -0.764248 (72, 1.59577\n",
+       "  (73, -0.466006 (74, -0.983965 (77, 0.509676 (79, 0.86618 (80, -0.767171\n",
+       "  (82, -0.955884 (83, -0.326832 (84, -0.764701 (87, -0.834976 (88, 0.846553\n",
+       "  (89, -0.578475 (90, -0.522823 (91, 0.802248 (92, 0.123631 (94, 0.696202\n",
+       "  (95, 0.0283147 (96, -0.999559 (97, 0.738769 (98, -0.368989 (99, 0.656419\n",
+       "  (100, 0.9001 }\n",
+       "val v5_s : t =\n",
+       "  {dim: 100\n",
+       "  (1, 1.45827 (2, -0.411059 (4, 0.404641 (5, 0.740514 (7, -1.20533\n",
+       "  (8, -0.977894 (9, 0.43281 (10, -0.692304 (11, -0.00855015 (15, 1.44575\n",
+       "  (16, -1.52814 (17, 0.497091 (19, -0.8659 (20, -0.572763 (21, -0.963705\n",
+       "  (23, 0.568959 (24, 0.245564 (25, -0.697603 (26, 0.706857 (27, 0.736393\n",
+       "  (29, 0.874151 (30, -1.40354 (31, -0.750514 (32, 0.392582 (34, 1.26771\n",
+       "  (36, 0.988593 (38, 0.0266769 (39, 0.78555 (40, 0.720996 (41, 0.978861\n",
+       "  (42, -1.18533 (43, -1.22443 (44, 0.734224 (45, 0.634506 (46, 0.672682\n",
+       "  (47, -0.481123 (48, 0.800156 (49, -0.132254 (50, 1.41289 (51, 0.47082\n",
+       "  (52, -0.731985 (53, 0.501758 (54, 0.180688 (55, -0.422431 (56, -0.067584\n",
+       "  (57, -1.47335 (58, -0.301306 (59, 0.917181 (60, -0.391153 (61, 0.936169\n",
+       "  (62, -0.855439 (63, -0.730839 (64, -0.763087 (65, -0.777606 (66, -0.280911\n",
+       "  (67, 1.44045 (68, -0.312286 (69, -0.166879 (71, -0.764248 (72, -0.366148\n",
+       "  (73, -1.2337 (74, -0.983965 (77, -0.509676 (79, -0.86618 (80, 0.767171\n",
+       "  (82, 0.955884 (83, 0.326832 (84, -0.764701 (87, -0.834976 (88, -0.846553\n",
+       "  (89, 0.578475 (90, 0.522823 (91, -0.802248 (92, -1.82724 (94, 0.696202\n",
+       "  (95, 1.66064 (96, 0.999559 (97, -0.738769 (98, 0.368989 (99, 0.656419\n",
+       "  (100, -0.9001 }\n",
+       "val v6_s : t =\n",
+       "  {dim: 100\n",
+       "  (1, 1.95004 (2, 0.411059 (4, 2.53041 (5, -0.740514 (7, -2.06675\n",
+       "  (8, 0.977894 (9, -0.43281 (10, -2.07691 (11, -3.91332 (15, 2.45167\n",
+       "  (16, -1.13229 (17, -0.497091 (19, 0.8659 (20, 0.572763 (21, 0.963705\n",
+       "  (23, -0.568959 (24, 3.31078 (25, 0.697603 (26, -0.706857 (27, 2.20918\n",
+       "  (29, -0.874151 (30, -1.97145 (31, -2.25154 (32, -0.392582 (34, 1.84797\n",
+       "  (36, -0.988593 (38, -3.18907 (39, -0.78555 (40, 2.16299 (41, 2.93658\n",
+       "  (42, -1.53222 (43, -2.18995 (44, -0.734224 (45, -0.634506 (46, 3.23606\n",
+       "  (47, -2.76547 (48, -0.800156 (49, -2.67945 (50, 2.17867 (51, -0.47082\n",
+       "  (52, 0.731985 (53, -0.501758 (54, -2.88344 (55, 0.422431 (56, 3.07592\n",
+       "  (57, -1.03175 (58, 0.301306 (59, -0.917181 (60, 0.391153 (61, -0.936169\n",
+       "  (62, 0.855439 (63, 0.730839 (64, 0.763087 (65, 0.777606 (66, 2.93956\n",
+       "  (67, 1.98261 (68, 0.312286 (69, 2.86117 (71, -2.29274 (72, 2.82539\n",
+       "  (73, -2.16571 (74, -2.9519 (77, 0.509676 (79, 0.86618 (80, -0.767171\n",
+       "  (82, -0.955884 (83, -0.326832 (84, -2.2941 (87, -2.50493 (88, 0.846553\n",
+       "  (89, -0.578475 (90, -0.522823 (91, 0.802248 (92, -1.57998 (94, 2.0886\n",
+       "  (95, 1.71727 (96, -0.999559 (97, 0.738769 (98, -0.368989 (99, 1.96926\n",
+       "  (100, 0.9001 }\n"
+      ]
+     },
+     "execution_count": 26,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val zero : Lacaml.D.vec = R1 R2 R3     R98 R99 R100\n",
+       "                           0  0  0 ...   0   0    0\n",
+       "val zero_s : t = {dim: 100 }\n"
+      ]
+     },
+     "execution_count": 26,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "let x1 = L.Vec.map (fun x -> if abs_float x < 0.6 then 0. else x) (L.Vec.random 100)\n",
+    "and x2 = L.Vec.map (fun x -> if abs_float x < 0.3 then 0. else x) (L.Vec.random 100)                                                                                                            \n",
+    "\n",
+    "let x3 = L.Vec.map (fun x -> 2. *. x) x1\n",
+    "and x4 = L.Vec.add x1 x2\n",
+    "and x5 = L.Vec.sub x1 x2\n",
+    "and x6 = \n",
+    "  let v = L.copy x2 in\n",
+    "  L.axpy ~alpha:3. x1 v;\n",
+    "  v \n",
+    "\n",
+    "  \n",
+    "let v1 = x1\n",
+    "and v2 = x2\n",
+    "and v3 = x3 \n",
+    "and v4 = x4 \n",
+    "and v5 = x5 \n",
+    "and v6 = x6 \n",
+    "\n",
+    "  \n",
+    "let v1_s = of_vec x1\n",
+    "and v2_s = of_vec x2\n",
+    "and v3_s = of_vec x3\n",
+    "and v4_s = of_vec x4\n",
+    "and v5_s = of_vec x5\n",
+    "and v6_s = of_vec x6\n",
+    "\n",
+    "    \n",
+    "let zero   = L.Vec.make0 100\n",
+    "and zero_s = of_vec (L.Vec.make0 100)\n",
+    "\n",
+    "  \n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 27,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "val test_conversion : unit -> unit = <fun>\n"
+      ]
+     },
+     "execution_count": 27,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val test_operations : unit -> unit = <fun>\n"
+      ]
+     },
+     "execution_count": 27,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val test_dot : unit -> unit = <fun>\n"
+      ]
+     },
+     "execution_count": 27,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/plain": [
+       "val test_case : unit -> (string * [> `Quick ] * (unit -> unit)) list = <fun>\n"
+      ]
+     },
+     "execution_count": 27,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "  let test_conversion () =\n",
+    "    Alcotest.(check bool) \"sparse -> dense  1\" true (to_vec v1_s = v1  );\n",
+    "    Alcotest.(check bool) \"sparse -> dense  2\" true (to_vec v2_s = v2  );\n",
+    "    Alcotest.(check bool) \"dense  -> sparse 1\" true (of_vec v1   = v1_s);\n",
+    "    Alcotest.(check bool) \"dense  -> sparse 2\" true (of_vec v2   = v2_s)\n",
+    " \n",
+    "  \n",
+    "  let test_operations () =\n",
+    "    Alcotest.(check  bool)  \"dense   scale\"        true  (let w = L.copy v1 in L.scal 2. w ; w  =  v3);\n",
+    "    Alcotest.(check  bool)  \"sparse  scale\"        true  (scale  2.    v1_s  =  v3_s);\n",
+    "    \n",
+    "    Alcotest.(check  bool)  \"dense   dense   add\"  true  (L.Vec.add  v1  v2    =  v4);\n",
+    "    (*\n",
+    "    Alcotest.(check  bool)  \"dense   sparse  add\"  true  (add    v1    v2_s  =  v4_s);\n",
+    "    Alcotest.(check  bool)  \"sparse  dense   add\"  true  (add    v1_s  v2    =  v4_s);\n",
+    "    Alcotest.(check  bool)  \"sparse  dense   add\"  true  (add    v1    v2_s  =  v4_s);\n",
+    "    *)\n",
+    "    Alcotest.(check  bool)  \"sparse  sparse  add\"  true  (equal (add    v1_s  v2_s)  v4_s);\n",
+    "    \n",
+    "    Alcotest.(check  bool)  \"dense   dense   sub\"  true  (L.Vec.sub    v1    v2    =  v5);\n",
+    "    (*\n",
+    "    Alcotest.(check  bool)  \"dense   sparse  sub\"  true  (sub    v1    v2_s  =  v5_s);\n",
+    "    Alcotest.(check  bool)  \"sparse  dense   sub\"  true  (sub    v1_s  v2    =  v5_s);\n",
+    "    Alcotest.(check  bool)  \"sparse  dense   sub\"  true  (sub    v1    v2_s  =  v5_s);\n",
+    "    *)\n",
+    "    Alcotest.(check  bool)  \"sparse  sparse  sub\"  true  (equal (sub v1_s v2_s) v5_s);\n",
+    "    \n",
+    "    Alcotest.(check  bool)  \"dense   dense   sub\"  true  (L.Vec.sub  v1 v1   =  zero);\n",
+    "    (*\n",
+    "    Alcotest.(check  bool)  \"dense   sparse  sub\"  true  (sub    v1    v1_s  =  zero_s);\n",
+    "    Alcotest.(check  bool)  \"sparse  dense   sub\"  true  (sub    v1_s  v1    =  zero_s);\n",
+    "    *)\n",
+    "    Alcotest.(check  bool)  \"sparse  sparse  sub\"  true  (equal (sub v1_s v1_s) zero_s);\n",
+    "    \n",
+    "    Alcotest.(check  bool)  \"dense   dense   axpy\"  true  (let w = L.copy v2 in L.axpy ~alpha:3. v1  w ;  w  =  v6);\n",
+    "    (*\n",
+    "    Alcotest.(check  bool)  \"dense   sparse  axpy\"  true  (sub ~threshold:1.e-12 (axpy ~alpha:3.  v1    v2_s) v6_s = zero_s);\n",
+    "    Alcotest.(check  bool)  \"sparse  dense   axpy\"  true  (sub ~threshold:1.e-12 (axpy ~alpha:3.  v1_s  v2) v6_s = zero_s);\n",
+    "    *)\n",
+    "    Alcotest.(check  bool)  \"sparse  sparse  axpy\"  true  (equal (sub ~threshold:1.e-12 (axpy ~alpha:3.  v1_s  v2_s) v6_s) zero_s)\n",
+    "  \n",
+    "let test_dot () =  \n",
+    "    let d1d2 = L.dot x1 x2\n",
+    "    and d1d1 = L.dot x1 x1\n",
+    "    and d2d2 = L.dot x2 x2 \n",
+    "    in\n",
+    "    (*\n",
+    "    Alcotest.(check (float 1.e-10)) \"sparse x dense  1\" (dot v1_s v2  )  d1d2;\n",
+    "    Alcotest.(check (float 1.e-10)) \"sparse x dense  2\" (dot v1_s v1  )  d1d1;\n",
+    "    Alcotest.(check (float 1.e-10)) \"sparse x dense  3\" (dot v2_s v2  )  d2d2;\n",
+    "    Alcotest.(check (float 1.e-10)) \"dense  x sparse 1\" (dot v1   v2_s)  d1d2;\n",
+    "    Alcotest.(check (float 1.e-10)) \"dense  x sparse 2\" (dot v1   v1_s)  d1d1;\n",
+    "    Alcotest.(check (float 1.e-10)) \"dense  x sparse 3\" (dot v2   v2_s)  d2d2;\n",
+    "    *)\n",
+    "    Alcotest.(check (float 1.e-10)) \"sparse x sparse 1\" (dot v1_s v2_s)  d1d2;\n",
+    "    Alcotest.(check (float 1.e-10)) \"sparse x sparse 2\" (dot v1_s v1_s)  d1d1;\n",
+    "    Alcotest.(check (float 1.e-10)) \"sparse x sparse 3\" (dot v2_s v2_s)  d2d2\n",
+    "    \n",
+    "    \n",
+    "let test_case () = \n",
+    "  [ \n",
+    "    \"Conversion\", `Quick, test_conversion;\n",
+    "    \"Operations\", `Quick, test_operations;\n",
+    "    \"Dot product\", `Quick, test_dot;\n",
+    "  ] "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 28,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "File \"[28]\", line 1, characters 0-3:\n",
+      "Warning 1: this `(*' is the start of a comment.\n",
+      "Hint: Did you forget spaces when writing the infix operator `( * )'?\n"
+     ]
+    }
+   ],
+   "source": [
+    "(*)\n",
+    "Alcotest.run ~argv:[|\"ignored\"|] \"Unit tests\" [\n",
+    "    \"SpVec\", test_case ();\n",
+    "];;\n",
+    "Printf.printf \"%!\";;\n",
+    "*)"
+   ]
   }
  ],
  "metadata": {