clGetPlatformID error when running OpenCL program. - opencl

Question

I've been trying to make OpenCL work in my laptop. I followed this link for that. I have an NVIDIA GT525M video card and Windows 8.1.
The steps I followed were:
Installing the up-to-date NVIDIA drivers.
Installing Visual Studio 2013 Community Edition.
Adding the paths for the linker and the compiler.
and then I tried to run the following code as given in that page:
#include <stdio.h>
#include <CL/cl.h>
int main(void)
{
cl_int err;
cl_uint* numPlatforms=NULL;
err = clGetPlatformIDs(0, NULL,numPlatforms);
if (CL_SUCCESS == err)
printf("\nDetected OpenCL platforms: %d", numPlatforms);
else
printf("\nError calling clGetPlatformIDs. Error code: %d", err);
getchar();
return 0;
}
The code builds successfully but the result I get is:
Error calling clGetPlatformIDs. Error code: -30
I get zero as the number of platforms.
I've been looking all over the internet for a solution but couldn't find one. Please help.

Answer 1

This:
cl_uint* numPlatforms=NULL;
err = clGetPlatformIDs(0, NULL,numPlatforms);
Is equivalent to this:
err = clGetPlatformIDs(0, NULL, NULL);
Which doesn't make sense. As per the documentation:
Returns CL_SUCCESS if the function is executed successfully. Otherwise it returns CL_INVALID_VALUE if num_entries is equal to zero and platforms is not NULL, or if both num_platforms and platforms are NULL.
CL_INVALID_VALUE is the -30 you are getting, for the reasons stated above.
What you really want is the following:
cl_uint numPlatforms = 0;
err = clGetPlatformIDs(0, NULL, &numPlatforms);