From: Szilárd Páll <pall.szilard@gmail.com>
Date: Tue, 17 Dec 2019 12:43:00 +0000 (+0100)
Subject: Comment the use of waitCoordinatesCopiedToDevice
X-Git-Url: http://biod.pnpi.spb.ru/gitweb/?a=commitdiff_plain;h=ce0423db6705dc264e58fd983e55468274040604;p=alexxy%2Fgromacs.git

Comment the use of waitCoordinatesCopiedToDevice

Tthis is to note that we are only using a barrier a mechanism to sync
with GPU tasks rather than to preventing a race between the copy and
other CPU tasks.

Change-Id: I8d432f7ef3e87e56beffa7f58230e50bcd59a666
---

diff --git a/src/gromacs/mdrun/md.cpp b/src/gromacs/mdrun/md.cpp
index db8fb0bdf8..97c3afa664 100644
--- a/src/gromacs/mdrun/md.cpp
+++ b/src/gromacs/mdrun/md.cpp
@@ -1424,6 +1424,9 @@ void gmx::LegacySimulator::do_md()
                     if (useGpuForUpdate)
                     {
                         stateGpu->copyCoordinatesToGpu(state->x, AtomLocality::Local);
+                        // Here we block until the H2D copy completes because event sync with the
+                        // force kernels that use the coordinates on the next steps is not implemented
+                        // (not because of a race on state->x being modified on the CPU while H2D is in progress).
                         stateGpu->waitCoordinatesCopiedToDevice(AtomLocality::Local);
                     }
                 }