Improvements to machine_hierarchy code for re-sizing

[jlpeyton]

Summary

These changes include:

1. Machine hierarchy now uses the base_num_threads field to indicate the maximum number of threads the current hierarchy can handle without a resize.
2. In __kmp_get_hierarchy, we need to get depth after any potential resize is done.
3. Cleanup of hierarchy resize code to support 1 above.

[tlwilmar]

LGTM

openmp/trunk/runtime/src/kmp_affinity.h

void init(AddrUnsPair *adr2os, int num_addrs)
         uninitialized = initialized; // One writer
 
     }
 
     // Resize the hierarchy if nproc changes to something larger than before
     void resize(kmp_uint32 nproc)
     {
         kmp_int8 bool_result = KMP_COMPARE_AND_STORE_ACQ8(&resizing, 0, 1);
-        if (bool_result == 0) { // Someone else is resizing
-            while (TCR_1(resizing) != 0) KMP_CPU_PAUSE();
+        while (bool_result == 0) { // someone else is trying to resize
+            KMP_CPU_PAUSE();
+            if (nproc <= base_num_threads)  // happy with other thread's resize
                 return;
+            else // try to resize
+                bool_result = KMP_COMPARE_AND_STORE_ACQ8(&resizing, 0, 1);
         }
         KMP_DEBUG_ASSERT(bool_result!=0);
-        KMP_DEBUG_ASSERT(nproc > base_num_threads);
+        if (nproc <= base_num_threads) return; // happy with other thread's resize
 
         // Calculate new maxLevels
         kmp_uint32 old_sz = skipPerLevel[depth-1];
         kmp_uint32 incs = 0, old_maxLevels = maxLevels;
-  // First see if old maxLevels is enough to contain new size
+        // First see if old maxLevels is enough to contain new size
         for (kmp_uint32 i=depth; i<maxLevels && nproc>old_sz; ++i) {
             skipPerLevel[i] = 2*skipPerLevel[i-1];
+            numPerLevel[i-1] *= 2;
             old_sz *= 2;
             depth++;
         }
-  if (nproc <= old_sz) // enough space already
-      return;
-  // Not enough space, need to expand hierarchy
+        if (nproc > old_sz) { // Not enough space, need to expand hierarchy
             while (nproc > old_sz) {
                 old_sz *=2;
                 incs++;
-      depth++;
-  }
+                depth++;
+            }
             maxLevels += incs;
 
             // Resize arrays
             kmp_uint32 *old_numPerLevel = numPerLevel;
             kmp_uint32 *old_skipPerLevel = skipPerLevel;
             numPerLevel = skipPerLevel = NULL;
             numPerLevel = (kmp_uint32 *)__kmp_allocate(maxLevels*2*sizeof(kmp_uint32));
             skipPerLevel = &(numPerLevel[maxLevels]);
 
             // Copy old elements from old arrays
             for (kmp_uint32 i=0; i<old_maxLevels; ++i) { // init numPerLevel[*] to 1 item per level
                 numPerLevel[i] = old_numPerLevel[i];
                 skipPerLevel[i] = old_skipPerLevel[i];
             }
 
             // Init new elements in arrays to 1
             for (kmp_uint32 i=old_maxLevels; i<maxLevels; ++i) { // init numPerLevel[*] to 1 item per level
                 numPerLevel[i] = 1;
                 skipPerLevel[i] = 1;
             }
 
             // Free old arrays
             __kmp_free(old_numPerLevel);
+        }
 
         // Fill in oversubscription levels of hierarchy
         for (kmp_uint32 i=old_maxLevels; i<maxLevels; ++i)
             skipPerLevel[i] = 2*skipPerLevel[i-1];
 
         base_num_threads = nproc;
         resizing = 0; // One writer
 
     }
 };
 #endif // KMP_AFFINITY_H

openmp/trunk/runtime/src/kmp_affinity.cpp

 }
 
 void __kmp_get_hierarchy(kmp_uint32 nproc, kmp_bstate_t *thr_bar) {
     kmp_uint32 depth;
     // The test below is true if affinity is available, but set to "none". Need to init on first use of hierarchical barrier.
     if (TCR_1(machine_hierarchy.uninitialized))
         machine_hierarchy.init(NULL, nproc);
 
-    depth = machine_hierarchy.depth;
-    KMP_DEBUG_ASSERT(depth > 0);
     // Adjust the hierarchy in case num threads exceeds original
-    if (nproc > machine_hierarchy.skipPerLevel[depth-1])
+    if (nproc > machine_hierarchy.base_num_threads)
         machine_hierarchy.resize(nproc);
 
+    depth = machine_hierarchy.depth;
+    KMP_DEBUG_ASSERT(depth > 0);
+
     thr_bar->depth = depth;
     thr_bar->base_leaf_kids = (kmp_uint8)machine_hierarchy.numPerLevel[0]-1;
     thr_bar->skip_per_level = machine_hierarchy.skipPerLevel;
 }
 
 #if KMP_AFFINITY_SUPPORTED
 
 //