diff --git a/Makefile b/Makefile
index 4444cc8..77d1681 100644
--- a/Makefile
+++ b/Makefile
@@ -36,7 +36,7 @@ src/MAIN/qmc src/MAIN/qmc_create_walkers src/MAIN/qmcchem_info: lib/libezfio.a l
 # OCaml
 # -----
 
-ocaml/qmcchem: EZFIO/Ocaml/ezfio.ml ocaml/Property.ml
+ocaml/qmcchem: EZFIO/Ocaml/ezfio.ml $(wildcard ocaml/*.ml)
 	./scripts/compile_ocaml.sh
 
 # Archive
@@ -58,7 +58,7 @@ bin/qmcchem_info: src/MAIN/qmcchem_info
 bin/qmc_create_walkers: src/MAIN/qmc_create_walkers
 	cp src/MAIN/qmc_create_walkers bin/
 
-bin/qmcchem:
+bin/qmcchem: ocaml/qmcchem
 	cp ocaml/qmcchem bin/
 
 all: bin/qmc bin/qmcchem_info bin/qmc_create_walkers bin/qmcchem 
diff --git a/make.config.gfortran b/make.config.gfortran
index c1bca00..ac6352b 100644
--- a/make.config.gfortran
+++ b/make.config.gfortran
@@ -7,7 +7,7 @@ CPU_TYPE="-mavx"
 ## FORTRAN compiler
 FC="gfortran -ffree-line-length-none"
 FCFLAGS="-O2 -g ${CPU_TYPE}"
-LIB="-lblas -llapack"
+LIB="-lblas -llapack -lpthread"
 
 ## IRPF90
 IRPF90="${QMCCHEM_PATH}/bin/irpf90"
diff --git a/make.config.ifort b/make.config.ifort
index ce5434f..d241749 100644
--- a/make.config.ifort
+++ b/make.config.ifort
@@ -15,7 +15,7 @@ LIB="-mkl=sequential"
 
 ## IRPF90
 IRPF90="${QMCCHEM_PATH}/bin/irpf90"
-IRPF90_FLAGS="--align=${ALIGN} ${IRPF90_FLAGS}"
+IRPF90_FLAGS="--align=${ALIGN}"
 
 export FC FCFLAGS LIB IRPF90 IRPF90_FLAGS
 
diff --git a/ocaml/Qmcchem_dataserver.ml b/ocaml/Qmcchem_dataserver.ml
index 6242529..70c605d 100644
--- a/ocaml/Qmcchem_dataserver.ml
+++ b/ocaml/Qmcchem_dataserver.ml
@@ -48,10 +48,10 @@ let run ?(daemon=true) ezfio_filename =
   in
 
 
-  (** Measures the time difference between [t0] and [Unix.time ()] *)
+  (** Measures the time difference between [t0] and [Unix.gettimeofday ()] *)
   let delta_t t0 =
     let t1 =
-      Unix.time ()
+      Unix.gettimeofday ()
     in
     t1 -. t0
   in
@@ -149,7 +149,7 @@ let run ?(daemon=true) ezfio_filename =
       delta_t t0
     in
     let message = 
-      Printf.sprintf "%20s : %8d : %10s : %f" 
+      Printf.sprintf "%20s : %8d : %10s : %e" 
         socket size text dt 
     in
     Zmq.Socket.send debug_socket message
@@ -183,7 +183,7 @@ let run ?(daemon=true) ezfio_filename =
   (** Array of walkers. The size is [walk_num_tot]. *)
   let walkers_array = 
     let t0 = 
-      Unix.time ()
+      Unix.gettimeofday ()
     in
     let j =
       3*elec_num + 3
@@ -218,7 +218,7 @@ let run ?(daemon=true) ezfio_filename =
 
   (** Last time when the walkers were saved to disk. *)
   let last_save_walkers = 
-    ref (Unix.time ())
+    ref (Unix.gettimeofday ())
   in
 
 
@@ -227,7 +227,7 @@ let run ?(daemon=true) ezfio_filename =
     if (delta_t !last_save_walkers > 10. ) then
       begin
         let t0 =
-          Unix.time ()
+          Unix.gettimeofday ()
         in
         Ezfio.set_electrons_elec_coord_pool_size walk_num_tot ;
         let walkers_list = 
@@ -239,7 +239,7 @@ let run ?(daemon=true) ezfio_filename =
         Ezfio.set_electrons_elec_coord_pool (Ezfio.ezfio_array_of_list
           ~rank:3 ~dim:[| elec_num+1 ; 3 ; walk_num_tot |] ~data:walkers_list);
         send_log "status" walk_num_tot t0 "Saved walkers";
-        last_save_walkers := Unix.time ();
+        last_save_walkers := Unix.gettimeofday ();
       end
   in
 
@@ -292,7 +292,7 @@ let run ?(daemon=true) ezfio_filename =
     in
     match Hashtbl.find_opt workers_hash s with
     | Some _ -> failwith (s^" already registered")
-    | None   -> Hashtbl.add workers_hash s (Unix.time ()) 
+    | None   -> Hashtbl.add workers_hash s (Unix.gettimeofday ()) 
   in
 
 
@@ -310,12 +310,12 @@ let run ?(daemon=true) ezfio_filename =
 
 
 
-  (** Sets the last access of the worker to [Unix.time ()] *)
+  (** Sets the last access of the worker to [Unix.gettimeofday ()] *)
   let touch_worker w pid = 
     let s = 
       key w pid
     in
-    Hashtbl.replace workers_hash s (Unix.time ())
+    Hashtbl.replace workers_hash s (Unix.gettimeofday ())
   in
 
 
@@ -386,7 +386,7 @@ let run ?(daemon=true) ezfio_filename =
   *)
   let compress_block_file filename =
     let t0 = 
-      Unix.time ()
+      Unix.gettimeofday ()
     in
     close_out !block_channel;
     Unix.rename block_channel_filename_locked block_channel_filename_tmp;
@@ -406,7 +406,7 @@ let run ?(daemon=true) ezfio_filename =
 
   let start_status_thread = 
       let t0 =
-        Unix.time ()
+        Unix.gettimeofday ()
       in
       Thread.create (fun () -> 
         send_log "status" 0 t0 "Starting status thread";
@@ -422,7 +422,7 @@ let run ?(daemon=true) ezfio_filename =
         in
 
         let start_time = 
-          Unix.time ()
+          Unix.gettimeofday ()
         and stop_time = 
           ref (Input.Stop_time.(read () |> to_float) )
         in
@@ -435,7 +435,7 @@ let run ?(daemon=true) ezfio_filename =
         do
           Unix.sleepf delay;
           let now =
-            Unix.time ()
+            Unix.gettimeofday ()
           in
           let status_string = 
             Status.to_string !status
@@ -490,7 +490,7 @@ let run ?(daemon=true) ezfio_filename =
 
   let start_log_thread = 
       let t0 =
-        Unix.time ()
+        Unix.gettimeofday ()
       in
       Thread.create (fun () -> 
         send_log "status" 0 t0 "Starting log thread";
@@ -520,7 +520,7 @@ let run ?(daemon=true) ezfio_filename =
                 |> String.concat " "
               in
               let now =
-                Unix.time ()
+                Unix.gettimeofday ()
               in
               send_log "log" 0 now message
             end
@@ -556,7 +556,7 @@ let run ?(daemon=true) ezfio_filename =
 
   let start_main_thread =
     let wall0 =
-    Unix.time ()
+    Unix.gettimeofday ()
     in
     let f () = 
     
@@ -627,7 +627,7 @@ let run ?(daemon=true) ezfio_filename =
           Zmq.Socket.recv_all ~block:false rep_socket
         in
         let t0 = 
-          Unix.time ()
+          Unix.gettimeofday ()
         in
         let msg =
           List.map String.trim raw_msg
@@ -712,7 +712,7 @@ let run ?(daemon=true) ezfio_filename =
           Zmq.Socket.recv_all ~block:false pull_socket
         in
         let t0 = 
-          Unix.time ()
+          Unix.gettimeofday ()
         in
         let msg =
           List.map String.trim raw_msg
@@ -746,7 +746,7 @@ let run ?(daemon=true) ezfio_filename =
               done;
               let wall =
                 Printf.sprintf "%f %f # %s %s %s %d"
-                  (Unix.time () -. wall0)
+                  (Unix.gettimeofday () -. wall0)
                   1. (Property.to_string Property.Wall)
                   hostname (string_of_int dataserver_pid) 1
                 |> Block.of_string 
@@ -838,7 +838,7 @@ let run ?(daemon=true) ezfio_filename =
   (** {3 Main function} *)
 
   let t0 = 
-    Unix.time ()
+    Unix.gettimeofday ()
   in
 
   (* Handle signals *)
diff --git a/ocaml/Qmcchem_forwarder.ml b/ocaml/Qmcchem_forwarder.ml
index f5bda97..929356b 100644
--- a/ocaml/Qmcchem_forwarder.ml
+++ b/ocaml/Qmcchem_forwarder.ml
@@ -466,6 +466,7 @@ let run ezfio_filename dataserver =
               int_of_string n_str
             in
             let len =
+              if !walk_num = 0 then n else
               n / !walk_num
             in
             if (n < 5*len) then
diff --git a/ocaml/Time.ml b/ocaml/Time.ml
index 8bc5afb..91c620f 100644
--- a/ocaml/Time.ml
+++ b/ocaml/Time.ml
@@ -39,7 +39,7 @@ let string_of_date t =
 
 
 let string_of_now () = 
-  Unix.time ()
+  Unix.gettimeofday ()
   |> Unix.localtime 
   |> string_of_date