Move the copy of the velocities for the output closer to the output

The D2H copy of velocities is split into two calls, one of which is
moved closer to the output, where it is consumed. This is in preparation
to creation a unified method to copy all data for the outuput when
it is needed.

Change-Id: I4b81aa95e2c0763bb3ebb4a7d8b18611765c54de

diff --git a/src/gromacs/mdrun/md.cpp b/src/gromacs/mdrun/md.cpp
index 4756c64ffe78f149d19f32f018e8f045b02d8ac3..b0b006b8bc785224c54251d7605f2184d1cb0e61 100644 (file)
--- a/src/gromacs/mdrun/md.cpp
+++ b/src/gromacs/mdrun/md.cpp
@@ -799,25 +799,16 @@ void gmx::LegacySimulator::do_md()
         do_verbose = mdrunOptions.verbose
                      && (step % mdrunOptions.verboseStepPrintInterval == 0 || bFirstStep || bLastStep);
 
-        if (useGpuForUpdate && !bFirstStep)
+        if (useGpuForUpdate && !bFirstStep && bNS)
         {
-            // Copy velocities from the GPU when needed:
-            // - On search steps to keep copy on host (device buffers are reinitialized).
-            // - When needed for the output.
-            if (bNS || do_per_step(step, ir->nstvout))
-            {
-                stateGpu->copyVelocitiesFromGpu(state->v, AtomLocality::Local);
-                stateGpu->waitVelocitiesReadyOnHost(AtomLocality::Local);
-            }
-
+            // Copy velocities from the GPU on search steps to keep a copy on host (device buffers are reinitialized).
+            stateGpu->copyVelocitiesFromGpu(state->v, AtomLocality::Local);
+            stateGpu->waitVelocitiesReadyOnHost(AtomLocality::Local);
             // Copy coordinate from the GPU when needed at the search step.
             // NOTE: The cases when coordinates needed on CPU for force evaluation are handled in sim_utils.
             // NOTE: If the coordinates are to be written into output file they are also copied separately before the output.
-            if (bNS)
-            {
-                stateGpu->copyCoordinatesFromGpu(state->x, AtomLocality::Local);
-                stateGpu->waitCoordinatesReadyOnHost(AtomLocality::Local);
-            }
+            stateGpu->copyCoordinatesFromGpu(state->x, AtomLocality::Local);
+            stateGpu->waitCoordinatesReadyOnHost(AtomLocality::Local);
         }
 
         if (bNS && !(bFirstStep && ir->bContinuation))
@@ -1124,7 +1115,13 @@ void gmx::LegacySimulator::do_md()
             stateGpu->copyCoordinatesFromGpu(state->x, AtomLocality::Local);
             stateGpu->waitCoordinatesReadyOnHost(AtomLocality::Local);
         }
-
+        // Copy velocities if needed for the output.
+        // NOTE: Copy on the search steps is done at the beginning of the step.
+        if (useGpuForUpdate && !bNS && do_per_step(step, ir->nstvout))
+        {
+            stateGpu->copyVelocitiesFromGpu(state->v, AtomLocality::Local);
+            stateGpu->waitVelocitiesReadyOnHost(AtomLocality::Local);
+        }
         // Copy forces for the output if the forces were reduced on the GPU (not the case on virial steps)
         // and update is offloaded hence forces are kept on the GPU for update and have not been
         // already transferred in do_force().