Poor cublas strmm() performance?

Accelerated Computing CUDA CUDA Programming and Performance
1

In my algorithm I’m making several calls to cublasStrmm (matrix multiply), all something like this:

cublasStrmm('r', 'u', 'n', 'n', 10000, 65, 1.0, A, 65, B, 10000);

So we have m=10000, n=65 and k=65.

I do 72 of these calls, and the total time taken is 645ms, so that’s 9ms per call

This seems a bit slow, even for the funny size matrices I’m using.

By my calculations

  • the number of fp operations per call is (65 * (65+1) / 2) * 2 * 10000 = 42900000

  • so the FLOPS acheived is 42900000 / 0.009 = 4766666666 (4.76 GFlops)

I was expecting something much higher than this? Is anyone else seeing similar performance? Or have I got my calculations wrong? :lol:

Thanks,

Alex

2

Here’s some test code… i get as output:

m=10000 k=65 n=65

execution time per call: 14.028479 ms

gflops = 3.058065

void main(int argc, char** argv) {

	float* A;

	float* B;

	int m = 10000;

	int k = 65;

	int n = k;

	int iters = 72;

	

	cublasInit();

	cublasStatus status = cublasAlloc(m * k, sizeof(float), (void**) &A);

	status = cublasAlloc(k * n, sizeof(float), (void**) &B);

	float* bigEmptySpace = new float[m*k];

	memset(bigEmptySpace, 0, m*k*sizeof(float));

	cublasSetMatrix(m, k, sizeof(float), bigEmptySpace, m, A, m);

	cublasSetMatrix(k, n, sizeof(float), bigEmptySpace, k, B, k);

	unsigned int timer;

	CUT_SAFE_CALL(cutCreateTimer(&timer));

	cutStartTimer(timer);

	for (int i = 0; i < iters; i++) {

  cublasStrmm('r', 'u', 'n', 'n', m, n, 1.0, A, n, B, m);

  cudaSync(); // my C-wrapper for cudaThreadSynchronize() - needed here or it hangs!!

	}

	cutStopTimer(timer);

	float timePerCall = cutGetTimerValue(timer) / iters;

	printf("m=%d k=%d n=%d\n", m, k, n);

	printf("execution time per call: %f ms\n", timePerCall);

	float flopsPerCall = (n * (n+1) / 2) * 2 * m;

	float seconds = timePerCall / 1000.0;

	float flops = flopsPerCall / seconds;

	float gflops = flops / 1000000000.0;

	printf("gflops = %f\n", gflops);

	cublasFree(A);

	cublasFree(B);

}
3

If you are still interested, maybe this post can help you:

http://forums.nvidia.com/index.php?showtopic=99094