make hwloc_topology_load in umf constructor optional

Author: lplewa

src/libumf.c

@@ -77,7 +77,20 @@ umf_result_t umfInit(void) {
 #if !defined(UMF_NO_HWLOC)
     // some benchmarks uses multiple forks, and topology initialization is very slow
     // so if we initialize topology before the first fork, we can get significant performance gain.
-    umfGetTopologyReduced();
+
+    const char *env = getenv("UMF_CONF");
+    // todo: decide if we enable or disable umfGetTopologyReduced with env variable
+    // todo: find better name for this string "umf.hwloc.init"
+    // todo: with merge to master replace this with CTL
+#if 1
+    if (env && strcmp(env, "umf.hwloc.init=y") == 0) {
+        umfGetTopologyReduced();
+    }
+#else
+    if (!env || strcmp(env, "umf.hwloc.init=n") != 0) {
+        umfGetTopologyReduced();
+    }
+#endif
 #endif
     return UMF_RESULT_SUCCESS;
 }