Temporarily disable adaptive sampling on GPU

Author: willend

mcstas-comps/examples/Prototypes/ODIN_TOF_train4/ESS_butterfly.comp

@@ -551,7 +551,9 @@ TRACE
   int train_index;
 
   long tmp;
-  
+
+  // temporarily disable any attempt at adaptive sampling on GPU
+  #ifndef OPENACC
   if (total_N_sent == 0) {
     tmp = N_trains;
   } else {
@@ -563,6 +565,7 @@ TRACE
 
   #pragma acc atomic write
   adaptive_N = tmp;
+  #endif
 
   for (train_index=0; train_index<adaptive_N; train_index++) {