Move CheckNan to end of loop on stages in timeIntegrator

    CheckNan was previously located after EvolveStage. However, EvolveStage
    updates the conservative variables and CheckNan checks the primitive
    variables. This reports the detection of a NaN to the next cycle. By
    moving CheckNan to the end of the loop on stages in timeIntegrator,
    so after the ConsToPrim, this PR ensures that we detect the NaN at
    the right cycle.

Author: nscepi

src/timeIntegrator.cpp

@@ -301,14 +301,6 @@ void TimeIntegrator::Cycle(DataBlock &data) {
     // evolve dt accordingly
     data.t += data.dt;
 
-    // Look for Nans every now and then (this actually cost a lot of time on GPUs
-    // because streams are divergent)
-    if(ncycles%checkNanPeriodicity==0) {
-      if(data.CheckNan()>0) {
-        throw std::runtime_error(std::string("Nan found after integration cycle"));
-      }
-    }
-
     // Compute next time_step during first stage
     if(stage==0) {
       if(!haveFixedDt) {
@@ -347,7 +339,15 @@ void TimeIntegrator::Cycle(DataBlock &data) {
 
     // Add back fargo velocity so that boundary conditions are applied on the total V
     if(data.haveFargo) data.fargo->AddVelocity(data.t);
-  }
+ 
+    // Look for Nans every now and then (this actually cost a lot of time on GPUs
+    // because streams are divergent)
+    if(ncycles%checkNanPeriodicity==0) {
+      if(data.CheckNan()>0) {
+        throw std::runtime_error(std::string("Nan found after integration cycle"));
+      }
+    }
+ }
   /////////////////////////////////////////////////
   // END STAGES LOOP                             //
   /////////////////////////////////////////////////