use a different RNG than default for codes_local_latency

codes/codes.h

@@ -38,9 +38,10 @@ still have a timestamp that is greater than g_tw_lookahead.
 #define CODES_MEAN_LOCAL_LATENCY 0.01
 static inline tw_stime codes_local_latency(tw_lp *lp)
 {
+    int r = g_tw_nRNG_per_lp-1;
     tw_stime tmp;
 
-    tmp = (1.1 * g_tw_lookahead) + tw_rand_exponential(lp->rng, CODES_MEAN_LOCAL_LATENCY);
+    tmp = (1.1 * g_tw_lookahead) + tw_rand_exponential(&lp->rng[r], CODES_MEAN_LOCAL_LATENCY);
 
     return(tmp);
 }

src/util/codes_mapping.c

@@ -469,6 +469,11 @@ void codes_mapping_setup_with_seed_offset(int offset)
       message_size = 256;
       printf("\n Warning: ross message size not defined, resetting it to %d", message_size);
   }
+
+  // we increment the number of RNGs used to let codes_local_latency use the
+  // last one
+  g_tw_nRNG_per_lp++;
+
   tw_define_lps(codes_mapping_get_lps_for_pe(), message_size, 0);
 
   // use a similar computation to codes_mapping_init to compute the lpids and
@@ -480,7 +485,7 @@ void codes_mapping_setup_with_seed_offset(int offset)
       for (tw_lpid l = 0; l < g_tw_nlp; l++){
           for (int i = 0; i < g_tw_nRNG_per_lp; i++){
               tw_rand_initial_seed(&g_tw_lp[l]->rng[i], (g_tw_lp[l]->gid +
-                          global_nlps * offset) * g_tw_rng_max + i);
+                          global_nlps * offset) * g_tw_nRNG_per_lp + i);
           }
       }
   }