gtest: dynamically generate tests based on test machine's GPU count (#467)

* gtest: dynamically generate tests based on test machine's GPU count

* Adjust test element size and bfloat16 threshold for up to 16 GPUs

test/test_ReduceScatter.cpp

@@ -10,6 +10,8 @@ namespace CorrectnessTests
 {
     TEST_P(ReduceScatterCorrectnessTest, Correctness)
     {
+         // Adjust numElements to be multiple of numDevices
+        numElements = (numElements/numDevices)*numDevices;
         if (numDevices > numDevicesAvailable) return;
         if (numElements % numDevices != 0) return;
 
@@ -61,7 +63,7 @@ namespace CorrectnessTests
                                 // Number of elements
                                 testing::Values(2520, 3026520),
                                 // Number of devices
-                                testing::Values(2,3,4,5,6,7,8),
+                                testing::Range(2,(GTESTS_NUM_GPUS+1)),
                                 // In-place or not
                                 testing::Values(false, true),
                                 testing::Values("")),