Add simple iteration option for regression runnersa dn save CPU

bench/bench_alloc_shrink_to_fit.cpp

@@ -132,21 +132,25 @@ void vector_test_template(unsigned int num_iterations, unsigned int num_elements
 
 int main(int argc, const char *argv[])
 {
-   #define SINGLE_TEST
-   #ifndef SINGLE_TEST
+   //#define SINGLE_TEST
+   #define SIMPLE_IT
+   #ifdef SINGLE_TEST
+      #ifdef NDEBUG
+      unsigned int numit [] =  { 10 };
+      #else
+      unsigned int numit [] =  { 50 };
+      unsigned int numele[] = { 2000 };
+      #endif
+   #elif defined SIMPLE_IT
+      unsigned int numit [] =  { 3 };
+      unsigned int numele[] = { 2000 };
+   #else
       #ifdef NDEBUG
       unsigned int numit [] =  { 100,   1000, 10000 };
       #else
       unsigned int numit [] =  { 10,   100, 1000 };
       #endif
       unsigned int numele [] = { 10000, 2000, 500   };
-   #else
-      #ifdef NDEBUG
-      unsigned int numit [] =  { 500 };
-      #else
-      unsigned int numit [] =  { 50 };
-      #endif
-      unsigned int numele [] = { 2000   };
    #endif
 
    bool csv_output = argc == 2 && (strcmp(argv[1], "--csv-output") == 0);