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关于cuda kernel能否调用printf（）函数

2016-01-10 14:23 603 查看
笔者最近想编译cuda kernel的代码，不知道何种原因，cuda-gdb总是进入不了cuda 的kernel代码。问了身边的大神们，他们表示自己也没有用过cuda-gdb调试程序。他们告诉我最简单的方式就是设置printf输出中间变量。可是笔者有疑惑了，cuda __device__ 打头的函数不是不支持调用host端的函数吗，为何printf能调？

我试着在kernel代码中加上printf（），编译

map.cu(28): error: calling a host function("printf") from a __device__/__global__ function("map_count") is not allowed

怎么会报错？然后又去网上找相关资料，也有人告诉我用cuPrintf（）函数，于是我把所有的printf全部改为cuPrinf.编译还是会报错，怎么办

最后我在stackoverflow上看到了以下内容


printing
from cuda kernels

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I am writing a cuda program and trying to print something inside the cuda kernels using the printf function. But when I am compiling the program then I am getting an error
error : calling a host function("printf") from a __device__/__global__ function("agent_movement_top") is not allowed

error MSB3721: The command ""C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v4.2\bin\nvcc.exe" -gencode=arch=compute_10,code=\"sm_10,compute_10\" --use-local-env --cl-version 2008 -ccbin "c:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin" -I"C:\ProgramData\NVIDIA Corporation\NVIDIA GPU Computing SDK 4.2\C\common\inc" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v4.2\include"  -G  --keep-dir "Debug" -maxrregcount=0  --machine 32 --compile  -g    -Xcompiler "/EHsc /nologo /Od /Zi  /MDd  " -o "Debug\test.cu.obj" "C:\Users\umdutta\Desktop\SANKHA_ALL_MATERIALS\PROGRAMMING_FOLDER\ABM_MODELLING_2D_3D\TRY_NUM_2\test_proj_test\test_proj\test_proj\test.cu"" exited with code 2.


I am using the card GTX 560 ti having a compute capability greater than 2.0 and when I have searched a bit about the printing from cuda kernels I also saw that I need to change the compiler from sm_10 to sm_2.0 to take the full advantage of the card. Also some
suggested for cuPrintf to serve the purpose. I am bit confused what should I do and what should be the simplest and quickest way to get the printouts on my console screen. If I need to change the nvcc compiler from 1.0 to 2.0 then what should I do? One more
thing I would like to mention that I am using windows 7.0 and programming in visual studio 2010. Thanks for all your help.

这个问题涉及到cuda的计算能力，在cuda计算能力2.0 以上才支持printf（这点我也不知道为何能调用printf）

于是笔者仔细看了自己的makefile文件，做了一下修改



注解掉了一部分，只保留-gencode=arch=compute_20,code=\"sm_20,compute_20\"(也就是使计算能力为2.0的选项编译它)

最后 make dbg=1，编译成功

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