Using clBLAS on MACOSX - c++

Question

I just installed clBLAS on my mac (Monterey 12.4) using brew :
brew install clblas
But I can't run the simple example given by the library :
#include <sys/types.h>
#include <stdio.h>
/* Include the clBLAS header. It includes the appropriate OpenCL headers */
#include <clBLAS.h>
/* This example uses predefined matrices and their characteristics for
* simplicity purpose.
*/
#define M 4
#define N 3
#define K 5
static const cl_float alpha = 10;
static const cl_float A[M*K] = {
11, 12, 13, 14, 15,
21, 22, 23, 24, 25,
31, 32, 33, 34, 35,
41, 42, 43, 44, 45,
};
static const size_t lda = K; /* i.e. lda = K */
static const cl_float B[K*N] = {
11, 12, 13,
21, 22, 23,
31, 32, 33,
41, 42, 43,
51, 52, 53,
};
static const size_t ldb = N; /* i.e. ldb = N */
static const cl_float beta = 20;
static cl_float C[M*N] = {
11, 12, 13,
21, 22, 23,
31, 32, 33,
41, 42, 43,
};
static const size_t ldc = N; /* i.e. ldc = N */
static cl_float result[M*N];
int main( void )
{
cl_int err;
cl_platform_id platform = 0;
cl_device_id device = 0;
cl_context_properties props[3] = { CL_CONTEXT_PLATFORM, 0, 0 };
cl_context ctx = 0;
cl_command_queue queue = 0;
cl_mem bufA, bufB, bufC;
cl_event event = NULL;
int ret = 0;
/* Setup OpenCL environment. */
err = clGetPlatformIDs( 1, &platform, NULL );
err = clGetDeviceIDs( platform, CL_DEVICE_TYPE_GPU, 1, &device, NULL );
props[1] = (cl_context_properties)platform;
ctx = clCreateContext( props, 1, &device, NULL, NULL, &err );
queue = clCreateCommandQueue( ctx, device, 0, &err );
/* Setup clBLAS */
err = clblasSetup( );
/* Prepare OpenCL memory objects and place matrices inside them. */
bufA = clCreateBuffer( ctx, CL_MEM_READ_ONLY, M * K * sizeof(*A),
NULL, &err );
bufB = clCreateBuffer( ctx, CL_MEM_READ_ONLY, K * N * sizeof(*B),
NULL, &err );
bufC = clCreateBuffer( ctx, CL_MEM_READ_WRITE, M * N * sizeof(*C),
NULL, &err );
err = clEnqueueWriteBuffer( queue, bufA, CL_TRUE, 0,
M * K * sizeof( *A ), A, 0, NULL, NULL );
err = clEnqueueWriteBuffer( queue, bufB, CL_TRUE, 0,
K * N * sizeof( *B ), B, 0, NULL, NULL );
err = clEnqueueWriteBuffer( queue, bufC, CL_TRUE, 0,
M * N * sizeof( *C ), C, 0, NULL, NULL );
/* Call clBLAS extended function. Perform gemm for the lower right sub-matrices */
err = clblasSgemm( clblasRowMajor, clblasNoTrans, clblasNoTrans,
M, N, K,
alpha, bufA, 0, lda,
bufB, 0, ldb, beta,
bufC, 0, ldc,
1, &queue, 0, NULL, &event );
/* Wait for calculations to be finished. */
err = clWaitForEvents( 1, &event );
/* Fetch results of calculations from GPU memory. */
err = clEnqueueReadBuffer( queue, bufC, CL_TRUE, 0,
M * N * sizeof(*result),
result, 0, NULL, NULL );
/* Release OpenCL memory objects. */
clReleaseMemObject( bufC );
clReleaseMemObject( bufB );
clReleaseMemObject( bufA );
/* Finalize work with clBLAS */
clblasTeardown( );
/* Release OpenCL working objects. */
clReleaseCommandQueue( queue );
clReleaseContext( ctx );
return ret;
}
I get the error :
Undefined symbols for architecture x86_64:
"_clblasSetup", referenced from:
_main in main.o
"_clblasSgemm", referenced from:
_main in main.o
"_clblasTeardown", referenced from:
_main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [Program] Error 1
I know this is a linker problem but I don't know how to solve it. I'm including OpenCL like I do for other project :
LDFLAGS=-framework OpenCL
I tried variations around :
LDFLAGS=-framework OpenCL -framework clblas
But nothing works. Sorry if the question is simple.
EDIT : I found with this question that cblas.h is in a
-framework Accelerate
But still no possibility to find clblas.h

Answer 1

I found the solution which was quite simple.
We only need to add the library in the makefile :
/usr/local/Cellar/clblas/2.12/lib/libclBLAS.dylib
And add the path to the header :
/usr/local/Cellar/clblas/2.12/include/
Paths may depend on your installation.