认识CUDA

CUDA

CUDA（Compute Unified Device Architecture），是显卡厂商NVIDIA推出的运算平台。 CUDA?是一种由NVIDIA推出的通用并行计算架构，该架构使GPU能够解决复杂的计算问题。 它包含了CUDA指令集架构（ISA）以及GPU内部的并行计算引擎。 开发人员可以使用C语言来为CUDA?架构编写程序，所编写出的程序可以在支持CUDA?的处理器上以超高性能运行。

?如果这是你第一次使用CUDA，在Linux系统中，你可能想使用以下命令来检查CUDA
编译器是否正确安装：

nvcc

使用nvidia-smi查询GPU信息

nvidia-smi

在运行时设置设备

CUDA_VISIBLE_DEVICES=2，nvidia驱动程序会屏蔽其他GPU，这时设备2作为设备0出现在应用程序中。

CUDA_VISIBLE_DEVICES=2，3 nvidia驱动程序将只使用ID为2和3的设备，并且会将设备ID分别映射为0和1。

使用运行时API查询GPU信息

checkDeviceInfor.cu

#include "../common/common.h"
#include <cuda_runtime.h>
#include <stdio.h>
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/*
 * Display a variety of information on the first CUDA device in this system,
 * including driver version, runtime version, compute capability, bytes of
 * global memory, etc.
 */
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int main(int argc, char **argv)
{
    printf("%s Starting...\n", argv[0]);
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    int deviceCount = 0;
    cudaGetDeviceCount(&deviceCount);
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    if (deviceCount == 0)
    {
        printf("There are no available device(s) that support CUDA\n");
    }
    else
    {
        printf("Detected %d CUDA Capable device(s)\n", deviceCount);
    }
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    int dev = 0, driverVersion = 0, runtimeVersion = 0;
    cudaDeviceProp deviceProp;
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    for(;  dev < deviceCount; dev++)
    {
        CHECK(cudaSetDevice(dev));
        CHECK(cudaGetDeviceProperties(&deviceProp, dev));
        printf("Device %d: \"%s\"\n", dev, deviceProp.name);
    }
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    cudaDriverGetVersion(&driverVersion);
    cudaRuntimeGetVersion(&runtimeVersion);
    printf("  CUDA Driver Version / Runtime Version          %d.%d / %d.%d\n",
           driverVersion / 1000, (driverVersion % 100) / 10,
           runtimeVersion / 1000, (runtimeVersion % 100) / 10);
    printf("  CUDA Capability Major/Minor version number:    %d.%d\n",
           deviceProp.major, deviceProp.minor);
    printf("  Total amount of global memory:                 %.2f GBytes (%llu "
           "bytes)\n", (float)deviceProp.totalGlobalMem / pow(1024.0, 3),
           (unsigned long long)deviceProp.totalGlobalMem);
    printf("  GPU Clock rate:                                %.0f MHz (%0.2f "
           "GHz)\n", deviceProp.clockRate * 1e-3f,
           deviceProp.clockRate * 1e-6f);
    printf("  Memory Clock rate:                             %.0f Mhz\n",
           deviceProp.memoryClockRate * 1e-3f);
    printf("  Memory Bus Width:                              %d-bit\n",
           deviceProp.memoryBusWidth);
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    if (deviceProp.l2CacheSize)
    {
        printf("  L2 Cache Size:                                 %d bytes\n",
               deviceProp.l2CacheSize);
    }
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    printf("  Max Texture Dimension Size (x,y,z)             1D=(%d), "
           "2D=(%d,%d), 3D=(%d,%d,%d)\n", deviceProp.maxTexture1D,
           deviceProp.maxTexture2D[0], deviceProp.maxTexture2D[1],
           deviceProp.maxTexture3D[0], deviceProp.maxTexture3D[1],
           deviceProp.maxTexture3D[2]);
    printf("  Max Layered Texture Size (dim) x layers        1D=(%d) x %d, "
           "2D=(%d,%d) x %d\n", deviceProp.maxTexture1DLayered[0],
           deviceProp.maxTexture1DLayered[1], deviceProp.maxTexture2DLayered[0],
           deviceProp.maxTexture2DLayered[1],
           deviceProp.maxTexture2DLayered[2]);
    printf("  Total amount of constant memory:               %lu bytes\n",
           deviceProp.totalConstMem);
    printf("  Total amount of shared memory per block:       %lu bytes\n",
           deviceProp.sharedMemPerBlock);
    printf("  Total number of registers available per block: %d\n",
           deviceProp.regsPerBlock);
    printf("  Warp size:                                     %d\n",
           deviceProp.warpSize);
    printf("  Maximum number of threads per multiprocessor:  %d\n",
           deviceProp.maxThreadsPerMultiProcessor);
    printf("  Maximum number of threads per block:           %d\n",
           deviceProp.maxThreadsPerBlock);
    printf("  Maximum sizes of each dimension of a block:    %d x %d x %d\n",
           deviceProp.maxThreadsDim[0],
           deviceProp.maxThreadsDim[1],
           deviceProp.maxThreadsDim[2]);
    printf("  Maximum sizes of each dimension of a grid:     %d x %d x %d\n",
           deviceProp.maxGridSize[0],
           deviceProp.maxGridSize[1],
           deviceProp.maxGridSize[2]);
    printf("  Maximum memory pitch:                          %lu bytes\n",
           deviceProp.memPitch);
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    exit(EXIT_SUCCESS);
}
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