Changed integral storage to Float32

Utils/FourIdxStorage.ml

@@ -2,8 +2,9 @@ let max_index = 1 lsl 14
 
 type index_pair = { first : int ; second : int }
 
+
 type storage_t = 
-  | Dense  of (float, Bigarray.float64_elt, Bigarray.fortran_layout) Bigarray.Genarray.t
+  | Dense  of (float, Bigarray.float32_elt, Bigarray.fortran_layout) Bigarray.Genarray.t
   | Sparse of (int, float) Hashtbl.t
 
 type t =
@@ -81,7 +82,7 @@ let create ~size sparsity =
     match sparsity with
     | `Dense ->
       let result = 
-        Bigarray.Genarray.create Float64 Bigarray.fortran_layout [| size ; size ; size ; size |]
+        Bigarray.Genarray.create Float32 Bigarray.fortran_layout [| size ; size ; size ; size |]
       in
       Bigarray.Genarray.fill result 0.;
       Dense result

Utils/FourIdxStorage.mli

@@ -0,0 +1,25 @@
+(** Storage for four-index data (integrals, density matrices, ...).
+
+There are two kinds of ordering of indices:
+
+- Physicist's : { \[ \langle i j | k l \rangle \] }
+- Chemist's   : { \[ ( i j | k l ) \] }
+
+*)
+
+type t
+
+val create : size:int -> [< `Dense | `Sparse ] -> t
+(** If [`Dense] is chosen, internally the data is stored as a 4-dimensional
+    [Bigarray]. Else, it is stored as a hash table.
+*)
+
+(** {2 Accessors} *)
+val get_chem : t -> int -> int -> int -> int -> float
+val get_phys : t -> int -> int -> int -> int -> float
+val set_chem : t -> int -> int -> int -> int -> float -> unit
+val set_phys : t -> int -> int -> int -> int -> float -> unit
+
+(** {2 I/O} *)
+val to_file : ?cutoff:float -> filename:string -> t -> unit
+(** Write the data to file, using the physicist's ordering. *)