On nodes with a number of cores that isn't a power of 2 an overrun

of the cpuid array was happening (COSMA4 has 24 cores per node).

There may be better solutions, one just refuses to accept invalid
ids using the existing calculation that runs cleanly to the next power of 2.


Former-commit-id: e698ada22eb1240257feb31505a55dfde386e105

src/engine.c

@@ -2011,11 +2011,17 @@ void engine_init ( struct engine *e , struct space *s , float dt , int nr_thread
                 cpuid[k] = k;
             }
         else {
+            /*  Get next highest power of 2. */
+            int maxint = 1;
+            while ( maxint < nr_cores )
+                maxint *= 2;
+
             cpuid[0] = 0;
             k = 1;
-            for ( i = 1 ; i < nr_cores ; i *= 2 )
-                for ( j = nr_cores / i / 2 ; j < nr_cores ; j += nr_cores / i )
-                    cpuid[k++] = j;
+            for ( i = 1 ; i < maxint ; i *= 2 )
+                for ( j = maxint / i / 2 ; j < maxint ; j += maxint / i )
+                    if ( j < nr_cores && j != 0 )
+                        cpuid[k++] = j;
             #ifdef WITHMPI
                 printf( "engine_init: cpu map is [ " );
             #else