From: Berk Hess <hess@kth.se>
Date: Sat, 4 Jul 2015 08:18:05 +0000 (+0200)
Subject: Fix bug in GPU list balancing
X-Git-Url: http://biod.pnpi.spb.ru/gitweb/?p=alexxy%2Fgromacs.git;a=commitdiff_plain;h=eea54d018709cb37261a071db80775e189337748

Fix bug in GPU list balancing

The function split_sci_entry could produce empty lists. This seems
not to have caused incorrect results, only slight extra processing
of empty workunits in the CUDA kernel. Incorrect Coulomb energies
could appear for empty lists with shift=CENTRAL, but that does not
seem to happen.

Refs #1767.

Change-Id: I0b0ff0a450734d4863f1e9636ff5741d4f1a68da
---

diff --git a/src/mdlib/nbnxn_search.c b/src/mdlib/nbnxn_search.c
index 9034e2e39f..1e11514713 100644
--- a/src/mdlib/nbnxn_search.c
+++ b/src/mdlib/nbnxn_search.c
@@ -3545,7 +3545,8 @@ static void split_sci_entry(nbnxn_pairlist_t *nbl,
                 nsp_cj4 += (nbl->cj4[cj4].imei[0].imask >> p) & 1;
             }
 
-            if (nsp_cj4 > 0 && nsp + nsp_cj4 > nsp_max)
+            /* Check if we should split at this cj4 to get a list of size nsp */
+            if (nsp > 0 && nsp + nsp_cj4 > nsp_max)
             {
                 /* Split the list at cj4 */
                 nbl->sci[sci].cj4_ind_end = cj4;