undefined cudaMalloc symbols

Question

I'm trying to compile the cublas example from the CUDA documentation

//Example 2. Application Using C and CUBLAS: 0-based indexing
//-----------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <cuda_runtime.h>
#include "cublas_v2.h"
#define M 6
#define N 5
#define IDX2C(i,j,ld) (((j)*(ld))+(i))

static __inline__ void modify (cublasHandle_t handle, float *m, int ldm, int n, int p, int q, float alpha, float beta){
    cublasSscal (handle, n-p, &alpha, &m[IDX2C(p,q,ldm)], ldm);
    cublasSscal (handle, ldm-p, &beta, &m[IDX2C(p,q,ldm)], 1);
}

int main (void){
    cudaError_t cudaStat;    
    cublasStatus_t stat;
    cublasHandle_t handle;
    int i, j;
    float* devPtrA;
    float* a = 0;
    a = (float *)malloc (M * N * sizeof (*a));
    if (!a) {
        printf ("host memory allocation failed");
        return EXIT_FAILURE;
    }
    for (j = 0; j < N; j++) {
        for (i = 0; i < M; i++) {
            a[IDX2C(i,j,M)] = (float)(i * M + j + 1);
        }
    }
    cudaStat = cudaMalloc ((void**)&devPtrA, M*N*sizeof(*a));
    if (cudaStat != cudaSuccess) {
        printf ("device memory allocation failed");
        return EXIT_FAILURE;
    }
    stat = cublasCreate(&handle);
    if (stat != CUBLAS_STATUS_SUCCESS) {
        printf ("CUBLAS initialization failed\n");
        return EXIT_FAILURE;
    }
    stat = cublasSetMatrix (M, N, sizeof(*a), a, M, devPtrA, M);
    if (stat != CUBLAS_STATUS_SUCCESS) {
        printf ("data download failed");
        cudaFree (devPtrA);
        cublasDestroy(handle);
        return EXIT_FAILURE;
    }
    modify (handle, devPtrA, M, N, 1, 2, 16.0f, 12.0f);
    stat = cublasGetMatrix (M, N, sizeof(*a), devPtrA, M, a, M);
    if (stat != CUBLAS_STATUS_SUCCESS) {
        printf ("data upload failed");
        cudaFree (devPtrA);
        cublasDestroy(handle);
        return EXIT_FAILURE;
    }
    cudaFree (devPtrA);
    cublasDestroy(handle);
    for (j = 0; j < N; j++) {
        for (i = 0; i < M; i++) {
            printf ("%7.0f", a[IDX2C(i,j,M)]);
        }
        printf ("\n");
    }
    free(a);
    return EXIT_SUCCESS;
}

I saved this file into "cudaexample.c" and am trying to compile with gcc cudaexample.c -I/usr/local/cuda/include -L/usr/local/cuda/lib -lcuda -lcublas

I get an undefined symbols error:

Undefined symbols for architecture x86_64:
  "_cudaFree", referenced from:
      _main in ccpPWjbO.o
  "_cudaMalloc", referenced from:
      _main in ccpPWjbO.o
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status

It seems like I've specified the commands properly as other symbols (e.g. cublasCreate) are found. Why are Free and Malloc not present?

Relevant details: OSX: 10.10.2 gcc: 4.8.4 (target: x86_64-apple-darwin14) Graphics: NVIDA GeForce GT 650M 1024 MB

I downloaded and installed the CUDA-6.5 toolkit

Answer 1

Those API functions (e.g. cudaMalloc) are contained in the CUDA runtime library. You are not linking against that library, so those symbols aren't found during the link phase.

Add -lcudart to your link flags:

-I/usr/local/cuda/include -L/usr/local/cuda/lib -lcuda -lcublas -lcudart

and it should fix that issue for you.

(-lcuda is only needed if you are using CUDA driver API functions. You can remove that if you wish.)