Fix two PME DLB trigger issues

[alexxy/gromacs.git] / src / gromacs / ewald / pme-load-balancing.cpp

diff --git a/src/gromacs/ewald/pme-load-balancing.cpp b/src/gromacs/ewald/pme-load-balancing.cpp
index f8facc562183a87e048b29f33b1a87766a935aa9..089361143ab59700537fdd283d5bb1c129a5bf02 100644 (file)
--- a/src/gromacs/ewald/pme-load-balancing.cpp
+++ b/src/gromacs/ewald/pme-load-balancing.cpp
@@ -934,11 +934,17 @@ void pme_loadbal_do(pme_load_balancing_t *pme_lb,
         {
             pme_lb->bBalance = dd_dlb_is_on(cr->dd);
         }
-        else
+        /* We should ignore the first timing to avoid timing allocation
+         * overhead. And since the PME load balancing is called just
+         * before DD repartitioning, the ratio returned by dd_pme_f_ratio
+         * is not over the last nstlist steps, but the nstlist steps before
+         * that. So the first useful ratio is available at step_rel=3*nstlist.
+         */
+        else if (step_rel >= 3*ir->nstlist)
         {
             if (DDMASTER(cr->dd))
             {
-                /* PME node load is too high, start tuning */
+                /* If PME rank load is too high, start tuning */
                 pme_lb->bBalance =
                     (dd_pme_f_ratio(cr->dd) >= loadBalanceTriggerFactor);
             }
@@ -1019,7 +1025,7 @@ void pme_loadbal_do(pme_load_balancing_t *pme_lb,
     }
 
     if (!pme_lb->bBalance &&
-        (!pme_lb->bSepPMERanks || (step_rel <= pme_lb->step_rel_stop)))
+        (!pme_lb->bSepPMERanks || step_rel > pme_lb->step_rel_stop))
     {
         /* We have just deactivated the balancing and we're not measuring PP/PME
          * imbalance during the first steps of the run: deactivate the tuning.