External calls are not supported - CUDA

Question

Objective is to call a device function available in another file, when i compile the global kernel it shows the following error *External calls are not supported (found non-inlined call to _Z6GoldenSectionCUDA)*.

Problematic Code (not the full code but where the problem arises), cat norm.h

# ifndef NORM_H_
# define NORM_H_
# include<stdio.h>

__device__ double invcdf(double prob, double mean, double stddev);

#endif

cat norm.cu

# include <norm.h>

__device__ double invcdf(double prob, double mean, double stddev) {
    return (mean + stddev*normcdfinv(prob));
       }

cat test.cu

# include <norm.h>
# include <curand.h>
# include <curand_kernel.h>

__global__ void phase2Kernel(double* out_profit, struct strategyHolder* strategy) {
       curandState seedValue;
       curand_init(threadIdx.x, 0, 0, &seedValue);
       double randomD = invcdf(curand_uniform_double( &seedValue ), 300, 80);
    }

nvcc -c norm.cu -o norm.o -I"."
nvcc -c test.cu -o test.o -I"."

Answer 1

You're trying to do separate compilation, which needs some special command line options. See the NVCC manual for details, but here's how to get your example to compile. I've targeted sm_20, but you can target sm_20 or later depending on what GPU you have. Separate compilation is not possible on older devices (sm_1x).

• You don't need to declare the __device__ function as extern in your header file, but if you have any static device variables they will need to be declared as extern

• Generate relocatable code for the device by compiling as shown below (-dc is the device equivalent of -c, see the manual for more information)

  nvcc -arch=sm_20 -dc norm.cu -o norm.o -I.
  nvcc -arch=sm_20 -dc test.cu -o test.o -I.
  

• Link the device parts of the code by calling nvlink before the final host link

  nvlink -arch=sm_20 norm.o test.o -o final.o