PG-PuReMD: add better checking for CUDA-capable devices.

PG-PuReMD/src/cuda_environment.cu

-
 #include "cuda_environment.h"
-
 #include "cuda_utils.h"
 
 extern "C" void Setup_Cuda_Environment (int rank, int nprocs, int gpus_per_node)
 {
 
-    int deviceCount = 0;
-    cudaGetDeviceCount (&deviceCount);
+    int deviceCount;
+    cudaError_t flag;
+    
+    flag = cudaGetDeviceCount (&deviceCount);
+
+    if ( flag != cudaSuccess )
+    {
+        fprintf( stderr, "ERROR: no CUDA capable device(s) found. Terminating...\n" );
+        exit( CANNOT_INITIALIZE );
+    }
 
     //Calculate the # of GPUs per processor
     //and assign the GPU for each process
-
-    //hpcc changes
-    //if (gpus_per_node == 2) {
+    //TODO: handle condition where # CPU procs > # GPUs
     cudaSetDevice ( (rank % (deviceCount)) );
-    //cudaSetDevice( 1 );
+
+#if defined(__CUDA_DEBUG__)
     fprintf( stderr, "p:%d is using GPU: %d \n", rank, (rank % deviceCount));
-    //} else {
-    //    cudaSetDevice ( 0 );
-    //}
+#endif
 
     ///////////////////////////////////////////////
     ///////////////////////////////////////////////
@@ -36,9 +39,9 @@ extern "C" void Setup_Cuda_Environment (int rank, int nprocs, int gpus_per_node)
     ///////////////////////////////////////////////
     ///////////////////////////////////////////////
     ///////////////////////////////////////////////
-
 }
 
+
 extern "C" void Cleanup_Cuda_Environment ()
 {
     cudaDeviceReset ();