CUDA - 将CPU变量传输到GPU __constant__变量 [英] CUDA - Transfering CPU variables to GPU __constant__ variables

问题描述

与CUDA一样，最基本的东西有时是最难的...

As anything with CUDA, the most basic things are sometimes the hardest...

所以...我只想将一个变量从CPU复制到

So...I just want to copy a variable from the CPU to a GPU's constant variable, and I am having a hard time.

这是我所拥有的：

__constant__ int contadorlinhasx_d;

int main(){

(...)
int contadorlinhasx=100;
     status=cudaMemcpyToSymbol(contadorlinhasx_d,contadorlinhasx,1*sizeof(int),0,cudaMemcpyHostToDevice);

我收到此错误

presortx.cu(222): error: no instance of overloaded function "cudaMemcpyToSymbol" matches the argument list
        argument types are: (int, int, unsigned long, int, cudaMemcpyKind)

有人可以帮助我吗？我知道这是一个愚蠢的错误，但我厌倦了谷歌，我花了差不多30分钟只是试图复制一个愚蠢的变量：/

Could anyone help me? I know it is some stupid error, but I am tired of googling it, and I have spent almost 30 minutes just trying to copy a stupid variable :/

提前感谢

推荐答案

您需要执行

cudaMemcpyToSymbol("contadorlinhasx_d",
                   &contadorlinhasx,
                   1*sizeof(int),
                   0,
                   cudaMemcpyHostToDevice);

[请注意，这是旧的API调用，现在已在CUDA 4.0及更高版本中弃用]

[Note this is the old API call, now deprecated in CUDA 4.0 and newer]

或

cudaMemcpyToSymbol(contadorlinhasx_d,
                   &contadorlinhasx,
                   1*sizeof(int),
                   0,
                   cudaMemcpyHostToDevice);

如果您查看 API文档，前两个参数是指针。第一个可以是字符串，这将强制在API内部（CUDA 4之前）或设备符号地址（CUDA 4及更高版本）的符号查找。第二个参数是副本的主机源内存的地址。编译器错误消息非常明确 - 您传递的参数类型错误，编译器无法在库中找到匹配的实例。

If you look at the API documentation, the first two arguments are pointers. The first can either be a string, which will force a symbol lookup internally in the API (pre CUDA 4), or a device symbol address (CUDA 4 and later). The second argument is the address of the host source memory for the copy. The compiler error message is pretty explicit - you are passing the wrong types of argument and the compiler can't find an instance in the library which matches.

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