[FEM] Elmer: fixes for multi-threading

- load the results depending on the used cores, not always the multi-thread results
- avoid unnecessary console output - this info is already output in tasks.py
- handle number of cores as int to save in total 2 conversions

src/Mod/Fem/femsolver/elmer/tasks.py

@@ -130,12 +130,12 @@ class Solve(run.Solve):
             self.pushStatus("Number of CPU cores to be used for the solver run: {}\n"
                             .format(num_cores))
             args = []
-            if int(num_cores) > 1:
+            if num_cores > 1:
                 if system() != "Windows":
                     args.extend(["mpirun"])
                 else:
                     args.extend(["mpiexec"])
-                args.extend(["-np", num_cores])
+                args.extend(["-np", str(num_cores)])
             args.extend([binary])
             if system() == "Windows":
                 self._process = subprocess.Popen(
@@ -283,16 +283,22 @@ class Results(run.Results):
         possible_post_file_old = os.path.join(self.directory, "case0001.vtu")
         possible_post_file_single = os.path.join(self.directory, "case_t0001.vtu")
         possible_post_file_multi = os.path.join(self.directory, "case_t0001.pvtu")
-        # first try the multi-thread result, then single then old name
-        if os.path.isfile(possible_post_file_multi):
-            postPath = possible_post_file_multi
-        elif os.path.isfile(possible_post_file_single):
-            postPath = possible_post_file_single
-        elif os.path.isfile(possible_post_file_old):
-            postPath = possible_post_file_old
-        else:
-            self.report.error("Result file not found.")
-            self.fail()
+        # depending on the currently set number of cores we try to load either
+        # the multi-thread result or the single result
+        if settings.get_cores("ElmerSolver") > 1:
+            if os.path.isfile(possible_post_file_multi):
+                postPath = possible_post_file_multi
+            else:
+                self.report.error("Result file not found.")
+                self.fail()
+        else:    
+            if os.path.isfile(possible_post_file_single):
+                postPath = possible_post_file_single
+            elif os.path.isfile(possible_post_file_old):
+                postPath = possible_post_file_old
+            else:
+                self.report.error("Result file not found.")
+                self.fail()
         return postPath
 
 ##  @}

src/Mod/Fem/femsolver/elmer/writer.py

@@ -241,9 +241,9 @@ class Writer(object):
                 )
             else:
                 subprocess.call(args, stdout=subprocess.DEVNULL)
-            if int(num_cores) > 1:
+            if num_cores > 1:
                 args = argsBasic
-                args.extend(["-partdual", "-metiskway", num_cores,
+                args.extend(["-partdual", "-metiskway", str(num_cores),
                              "-out", self.directory])
                 if system() == "Windows":
                     subprocess.call(

src/Mod/Fem/femsolver/settings.py

@@ -116,10 +116,6 @@ def get_cores(name):
     """
     if name in _SOLVER_PARAM:
         cores = _SOLVER_PARAM[name].get_cores()
-        FreeCAD.Console.PrintMessage(
-            "Number of CPU cores to be used for the solver run: {}\n"
-            .format(cores)
-        )
         return cores
     else:
         FreeCAD.Console.PrintError(
@@ -244,7 +240,7 @@ class _SolverDlg(object):
         return the_found_binary
 
     def get_cores(self):
-        cores = str(self.param_group.GetInt("UseNumberOfCores"))
+        cores = self.param_group.GetInt("UseNumberOfCores")
         return cores
 
     def get_write_comments(self):