CUDA __device__ 未解析的外部函数

2022-01-10 00:00:00 c linker-errors cuda c++

我正在尝试了解如何在单独的头文件中解耦 CUDA __device__ 代码.

I am trying to understand how to decouple CUDA __device__ codes in separate header files.

我有三个文件.

文件:1:int2.cuh

#ifndef INT2_H_
#define INT2_H_

#include "cuda.h"
#include "cuda_runtime.h"
#include "device_launch_parameters.h"

__global__ void kernel();
__device__ int k2(int k);

int launchKernel(int dim);

#endif /* INT2_H_ */

文件 2:int2.cu

#include "int2.cuh"
#include "cstdio"

__global__ void kernel() {
    int tid = threadIdx.x;
    printf("%d
", k2(tid));
}

__device__ int k2(int i) {
    return i * i;
}

int launchKernel(int dim) {
    kernel<<<1, dim>>>();
    cudaDeviceReset();
    return 0;
}

文件 3:CUDASample.cu

include <stdio.h>
#include <stdlib.h>
#include "int2.cuh"
#include "iostream"

using namespace std;

static const int WORK_SIZE = 256;

__global__ void sampleCuda() {
    int tid = threadIdx.x;
//    printf("%d
", k2(tid)); //Can not call k2
    printf("%d
", tid * tid);
}

int main(void) {

    int var;
    var = launchKernel(16);

    kernel<<<1, 16>>>();
    cudaDeviceReset();

    sampleCuda<<<1, 16>>>();
    cudaDeviceReset();

    return 0;
}

代码工作文件.我可以调用 sampleCuda() 内核(在同一个文件中)，调用 C 函数 launchKernel() (在其他文件中)，然后调用 kernel() 直接(在其他文件中).

The code works file. I can call the sampleCuda() kernel (in same file), call the C function launchKernel() (in other file), and call kernel() directly (in other file).

我面临的问题是从 sampleCuda() 内核调用 __device__ 函数.然后它显示以下错误.但是，在 kernel() 中可以调用相同的函数.

The problem I am facing is calling the __device__ function from sampleCuda() kernel. then it shows the following error. However, the same function is callable in kernel().

10:58:11 **** Incremental Build of configuration Debug for project CUDASample ****
make all 
Building file: ../src/CUDASample.cu
Invoking: NVCC Compiler
/Developer/NVIDIA/CUDA-6.5/bin/nvcc -G -g -O0 -gencode arch=compute_20,code=sm_20  -odir "src" -M -o "src/CUDASample.d" "../src/CUDASample.cu"
/Developer/NVIDIA/CUDA-6.5/bin/nvcc -G -g -O0 --compile --relocatable-device-code=false -gencode arch=compute_20,code=compute_20 -gencode arch=compute_20,code=sm_20  -x cu -o  "src/CUDASample.o" "../src/CUDASample.cu"
../src/CUDASample.cu(18): warning: variable "var" was set but never used

../src/CUDASample.cu(8): warning: variable "WORK_SIZE" was declared but never referenced

../src/CUDASample.cu(18): warning: variable "var" was set but never used

../src/CUDASample.cu(8): warning: variable "WORK_SIZE" was declared but never referenced

ptxas fatal   : Unresolved extern function '_Z2k2i'
make: *** [src/CUDASample.o] Error 255

10:58:14 Build Finished (took 2s.388ms)

推荐答案

问题是您在调用它的 __global__ 的单独编译单元中定义了一个 __device__ 函数.您需要通过添加 -dc 标志显式启用 可重定位设备代码 模式，或者将您的定义移动到同一单元.

The issue is that you defined a __device__ function in separate compilation unit from __global__ that calls it. You need to either explicitely enable relocatable device code mode by adding -dc flag or move your definition to the same unit.

来自 nvcc 文档:

From nvcc documentation:

--device-c|-dc 将每个 .c/.cc/.cpp/.cxx/.cu 输入文件编译成一个包含可重定位设备代码的目标文件.它相当于--relocatable-device-code=true --compile.

--device-c|-dc Compile each .c/.cc/.cpp/.cxx/.cu input file into an object file that contains relocatable device code. It is equivalent to --relocatable-device-code=true --compile.

参见CUDA C++ 设备代码的单独编译和链接 了解更多信息.

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