Kernels do not launch when -arch x86_64 is specified

Accelerated Computing CUDA CUDA Programming and Performance
1

I am running the following simple program:

#include "cuda.h"

#include "stdio.h"

#define SIZE 10

__global__  void vecAdd(float* A, float* B, float* C) {

// threadIdx.x is a built-in variable  provided by CUDA at runtime                                                                                               

  int i = threadIdx.x;

  A[i]=0;

  B[i]=i;

  C[i] = A[i] + B[i];

}

int main() {

int N=SIZE;

  float A, B, C;

  float *devPtrA;

  float *devPtrB;

  float *devPtrC;

  int memsize= SIZE * sizeof(float);

cudaMalloc((void**)&devPtrA, memsize);

  cudaMalloc((void**)&devPtrB, memsize);

  cudaMalloc((void**)&devPtrC, memsize);

cudaMemcpy(devPtrA, A, memsize,  cudaMemcpyHostToDevice);

  cudaMemcpy(devPtrB, B, memsize,  cudaMemcpyHostToDevice);

// __global__ functions are called:  Func<<< Dg, Db, Ns  >>>(parameter);                                                                                         

  vecAdd<<<1, N>>>(devPtrA,  devPtrB, devPtrC);

cudaError_t cudaResult;

  cudaResult = cudaGetLastError();

  if (cudaResult != cudaSuccess) {

    printf( "LAST ERROR: %s\n", cudaGetErrorString(cudaResult) );

  }

cudaMemcpy(C, devPtrC, memsize,  cudaMemcpyDeviceToHost);

for (int i=0; i<SIZE; i++)

    printf("C[%d]=%f\n",i,C[i]);

cudaFree(devPtrA);

  cudaFree(devPtrB);

  cudaFree(devPtrC);

}

The program runs without errors if I compile like this:

nvcc -o simpleadd simpleadd.cu

However, I am running on a 64 bit Mac Pro and need to be able to specify my 64-bit architecture like this:

nvcc -Xcompiler "-arch x86_64" -o simpleadd simpleadd.cu

This gives the error:

error: -malign-double makes no sense in the 64bit mode

which through exhaustive searching I realized could be “fixed” by compiling like this:

nvcc -Xcompiler "-arch x86_64" --no-align-double -o simpleadd simpleadd.cu

So now I run using

./simpleadd

and see this error in my output:

LAST ERROR: too many resources requested for launch

Supposedly, this error refers to using too many registers, but I can’t imagine this program is stretching any resources of the Quadro 4000 for mac in this machine. Does anyone have any idea what might be causing this? In my real project, I am calling CUDA functions from MEX files, and their compilation requires that I compile with the “arch x86_64” flag because the linker auto-detects my system architecture, so I really need to solve this.

People in this forums indicated that the “–ptxas-options=-v” option could be used to get more information about resource usage. My results were:

ptxas info : Compiling entry function ‘Z6vecAddPfS_S’ for ‘sm_10’

ptxas info : Used 4 registers, 12+16 bytes smem

Thanks for any help.

2

hm, I thought Mac supported -m64 as an nvcc option at this point for both host and device compilation. does that not work?

3

Thank you. I replaced the -Xcompiler “arch x86_64” compiler option with -m64 option to nvcc, and all my test programs seem to be working. This also obviated the need for the “–no-align-double” option I had been passing. In case this helps anyone, my machine is a 64-bit Mac Pro running Mac OS X version 10.6.6.

4 
int N=SIZE;

float A, B, C

That’s probably totally beside the point but this bit of code amused me. Is the compiler smart enough (or does it think it’s smart enough External Image ) to make this work?

This means it statically allocates an array of size N where N is, in fact, a mutable variable. Sure, it’s initialized by a constant, but it’s not defined as const int. Does this compile on your C++ compiler?

What if you add N++; before initializing the arrays?

5

uh, SIZE is a #define