?? ??? CUDA ??

? ???? NVIDIA? ?? ?? ??? ????? ????? ??? CUDA? ?? ?? ??? ?????. 2013?? CUDA? ?? ?? ???? ?? ???? ???? ?? ??? ???? CUDA ?????? ? ???? GPU? ?? ???? ??? ????? (??? ? ??) ??? ?????.

CUDA C++? CUDA? ??? ?? ??????? ?? ? ?? ?? ? ?????. ??? C++ ????? ??? ???? GPU?? ???? ?? ?? ?? ???? ???? ??? ????? ??? ? ????. ?? ???? ??? ???? ?? ? ???? ?? ???? ??????? ??????, ???? ? ???? ??? ?? ??? ???? ??? ????? ?????? ?????? ?????.

?? CUDA? ?? ??? ???????. ?? ???? ???????? ???? ??? ??????. C ?? C++ ??????? ? ??? ???? ?? ??? ? ????. ? ??? ????? CUDA ?? GPU? ??? ???(Windows, Mac ?? Linux, NVIDIA GPU? ?? ??) ?? GPU? ??? ???? ????(AWS, Azure, IBM SoftLayer ? ?? ???? ??? ?????? ??)? ?????. ?? ??? ???? CUDA ??? ???? ??? ???. ????? GPU?? ???? Jupyter ????? ??? ?? ????.

??? ???!

???? ????

?? ?? ?? ??? ?? ? ??? ??? ???? ??? C++ ?????? ???????.

#include <iostream>
#include <math.h>

// function to add the elements of two arrays
void add(int n, float *x, float *y)
{
  for (int i = 0; i < n; i++)
      y[i] = x[i] + y[i];
}

int main(void)
{
  int N = 1<<20; // 1M elements

  float *x = new float[N];
  float *y = new float[N];

  // initialize x and y arrays on the host
  for (int i = 0; i < N; i++) {
    x[i] = 1.0f;
    y[i] = 2.0f;
  }

  // Run kernel on 1M elements on the CPU
  add(N, x, y);

  // Check for errors (all values should be 3.0f)
  float maxError = 0.0f;
  for (int i = 0; i < N; i++)
    maxError = fmax(maxError, fabs(y[i]-3.0f));
  std::cout << "Max error: " << maxError << std::endl;

  // Free memory
  delete [] x;
  delete [] y;

  return 0;
}

?? ? C++ ????? ????? ?????. ?? ??? ??? ?? add.cpp?? ???? ??? ?? C++ ????? ???? ??????. ?? Mac? ???? ??? clang++? ???? ??? Linux??? g++?, Windows??? MSVC? ??? ? ????.

> clang++ add.cpp -o add

?? ?? ?????:

> ./add
 Max error: 0.000000

(Windows??? ?? ?? ??? add.exe? ???? .\add? ??? ? ????.)

???? ??? ??? ??? ??? ?? ?????. ?? ? ??? GPU? ?? ???? (???) ?????. ?? ? ?? ??? ???? ?? ? ????.

?? add ??? GPU? ??? ? ?? ??, ? CUDA? ??? ???? ?? ???. ??? ??? ??? __global__??? ???? ????? ?? ???, ?? CUDA C++ ????? ? ??? GPU?? ???? ???? CPU ???? ??? ? ??? ?????.

// CUDA Kernel function to add the elements of two arrays on the GPU
__global__
void add(int n, float *x, float *y)
{
  for (int i = 0; i < n; i++)
      y[i] = x[i] + y[i];
}

??? __global__ ??? ????? ??, GPU?? ???? ??? ?? ???? ???? ?? CPU?? ???? ??? ??? ???? ???.

CUDA? ??? ??

GPU?? ????? GPU?? ???? ? ?? ???? ???? ???. CUDA? ?? ???? ???? ?? GPU? CPU? ???? ? ?? ?? ??? ??? ???? ?? ?? ????. ?? ???? ???? ????? ???(CPU) ?? ?? ????(GPU) ???? ???? ? ?? ???? ???? cudaMallocManaged()? ???? ???. ???? ????? ???? cudaFree()? ???? ???.

? ???? new? ?? ??? cudaMallocManaged() ??? ??? delete []?? ?? ??? cudaFree? ?? ??? ???? ?? ???.

  // Allocate Unified Memory -- accessible from CPU or GPU
  float *x, *y;
  cudaMallocManaged(&x, N*sizeof(float));
  cudaMallocManaged(&y, N*sizeof(float));

  ...

  // Free memory
  cudaFree(x);
  cudaFree(y);

????? GPU?? ?? ???? add() ??? ???? ???. CUDA ?? ??? ?? ?? ?? ?? <<< >>>? ???? ?????. ???? ?? ?? ??? ??? add? ????? ?? ???.

add<<<1, 1>>>(N, x, y);

?????! ?? ?? ??? ?????? ? ??? ????????, ??? ? ?? add()? ???? ?? ??? GPU ???? ????? ?? ?? ???.

? ?? ?: CPU? ??? ??? ??? ????? ??? ????? ???(CUDA ?? ??? ???? CPU ???? ???? ????). ?? ?? CPU?? ?? ?? ??? ???? ?? cudaDeviceSynchronize()? ???? ???.

?? ??? ??? ????:

#include <iostream>
#include <math.h>
// Kernel function to add the elements of two arrays
__global__
void add(int n, float *x, float *y)
{
  for (int i = 0; i < n; i++)
    y[i] = x[i] + y[i];
}

int main(void)
{
  int N = 1<<20;
  float *x, *y;

  // Allocate Unified Memory – accessible from CPU or GPU
  cudaMallocManaged(&x, N*sizeof(float));
  cudaMallocManaged(&y, N*sizeof(float));

  // initialize x and y arrays on the host
  for (int i = 0; i < N; i++) {
    x[i] = 1.0f;
    y[i] = 2.0f;
  }

  // Run kernel on 1M elements on the GPU
  add<<<1, 1>>>(N, x, y);

  // Wait for GPU to finish before accessing on host
  cudaDeviceSynchronize();

  // Check for errors (all values should be 3.0f)
  float maxError = 0.0f;
  for (int i = 0; i < N; i++)
    maxError = fmax(maxError, fabs(y[i]-3.0f));
  std::cout << "Max error: " << maxError << std::endl;

  // Free memory
  cudaFree(x);
  cudaFree(y);
  
  return 0;
}

CUDA ??? ?? ???? .cu???. ??? ? ??? add.cu?? ??? ???? CUDA C++ ????? nvcc? ??????.

> nvcc add.cu -o add_cuda
> ./add_cuda
Max error: 0.000000

? ??? ???? ?? ???? ?? ??? ?? ??? ???? ??? ? ??? ?? ?????? ???? ??? ??? ? ?? ??? ????. ?? ?? ?? ?? ???? ?? ??? ?? ?? ??? ?? ??? ?????.

??: Windows? ?? Microsoft Visual Studio?? ????? ?? ???? ???? x64? ????? ???? ???.

???????!

??? ???? ? ??? ??? ???? ?? ??? ??? CUDA ??? ?? ???? ??? GPU ?????? nvprof? ??? ???? ????. ???? nvprof ./add_cuda? ????? ?? ???:

$ nvprof ./add_cuda
==3355== NVPROF is profiling process 3355, command: ./add_cuda
Max error: 0
==3355== Profiling application: ./add_cuda
==3355== Profiling result:
Time(%)      Time     Calls       Avg       Min       Max  Name
100.00%  463.25ms         1  463.25ms  463.25ms  463.25ms  add(int, float*, float*)
...

?? nvprof? ?? ????, add? ?? ??? ?????. NVIDIA Tesla K80 ?????? ? 0.5?? ???, 3?? ? Macbook Pro? NVIDIA GeForce GT 740M??? ?? ?? ??? ????.

?? ??? ? ??? ??? ???.

??? ????

?? ??? ???? ??? ???? ??? ????? ??? ??? ?? ? ????? ??? CUDA? <<<1, 1>>> ??? ????. ?? ?? ????? ??, CUDA ???? GPU?? ??? ? ??? ?? ??? ?? ?????. ???? ? ?? ????? ???, ?? ? ?? ????? ??? ??? ??? ?? ???? ??? ??? ?????. CUDA GPU? 32? ?? ??? ??? ??? ???? ??? ????? 256?? ???? ???? ?? ?????.

add<<<1, 256>>>(N, x, y);

? ?? ??? ??? ??? ???? ?? ???? ?? ??? ???? ?? ???? ? ?? ??? ?????. ?? ??? ????? ??? ???? ???. CUDA C++? ??? ?? ?? ???? ???? ??? ? ?? ???? ?????. ????? threadIdx.x? ?? ?? ? ?? ???? ???? ????, blockDim.x? ?? ? ??? ?? ?????. ?? ???? ??? ????? ??? ???????.

__global__
void add(int n, float *x, float *y)
{
  int index = threadIdx.x;
  int stride = blockDim.x;
  for (int i = index; i < n; i += stride)
      y[i] = x[i] + y[i];
}

add ??? ?? ???? ?????. ??? index?? 0?? ???? ?????(stride)? 1? ???? ? ?? ??? ????? ?????.

??? add_block.cu? ???? nvprof?? ?? ????? ?????. ? ?? ??? ????? ??? ?? ?? ????????.

Time(%)      Time     Calls       Avg       Min       Max  Name
100.00%  2.7107ms         1  2.7107ms  2.7107ms  2.7107ms  add(int, float*, float*)

?? ? ?? ??(463ms?? 2.7ms? ??)???, 1 ????? 256 ???? ???? ??? ??? ?? ????. K80? ? ?? ?? ?? GPU(3.2ms)?? ? ????. ? ?? ??? ?? ?? ???? ?????.

?? ???

CUDA GPU?? ???? ?????? ?? SM?? ???? ?? ?? ????? ????. ? SM? ?? ?? ?? ??? ??? ??? ? ????. ?? ??, ??? GPU ???? ??? Tesla P100 GPU?? 56?? SM? ???, ? SM? ?? 2048?? ?? ???? ??? ? ????. ? ?? ???? ??? ????? ?? ??? ???? ??? ???? ???.

?? ?? ??? ? ?? ????? ??? ??? ?? ????? ?? ????? ????. ?? ??? ??? ?? ????? ??? ?? ?????. ???? ? ??? N??? ??? ???? 256???? ?? N?? ???? ?? ?? ?? ?? ???? ???. N? ?? ??? ???? ?? ???(N? blockSize? ??? ?? ?? ???? ?????).

int blockSize = 256;
int numBlocks = (N + blockSize - 1) / blockSize;
add<<<numBlocks, blockSize>>>(N, x, y);

?? ??? ??? ?? ???? ????? ?? ??? ?????? ???. CUDA? ??? ? ?? ?? ???? gridDim.x? ??? ? ?? ??? ??? ???? ???? blockIdx.x? ?????. ?? 1? blockDim.x, gridDim.x ? threadIdx.x? ???? CUDA?? ??(1??)? ????? ??? ?????. ? ???? ??? ?? ??? ?? ???(?? ???? ?? ??: blockIdx.x * blockDim.x)? ???? ?? ??? ???? ???? ???(threadIdx.x) ??? ??? ???? ??? ????. blockIdx.x * blockDim.x + threadIdx.x ??? CUDA ??????.

__global__
void add(int n, float *x, float *y)
{
  int index = blockIdx.x * blockDim.x + threadIdx.x;
  int stride = blockDim.x * gridDim.x;
  for (int i = index; i < n; i += stride)
    y[i] = x[i] + y[i];
}

????? ??? ?? stride? ???? ? ??? ?(blockDim.x * gridDim.x)? ?????. CUDA ???? ??? ??? ??? grid-stride loop?? ???? ???.

??? add_grid.cu? ???? nvprof?? ?? ????? ?????.

Time(%)      Time     Calls       Avg       Min       Max  Name
100.00%  94.015us         1  94.015us  94.015us  94.015us  add(int, float*, float*)

K80? ?? SM?? ?? ??? ???? ??? 28? ?????! ??? K80?? 2?? GPU ? ??? ???? ???, ? GPU?? 13?? SM? ????. ? ???? GeForce?? 2?? (? ??) SM? ??? ??? ???? ? 680us? ????? ?? ?????.

??

??? Tesla K80 ? GeForce GT 750M?? ? ?? ??? add() ??? ??? ??? ????.

?????, GPU?? ?? ?? ???? ??? ? ????. ? ?? ??? ???? ?? ????? GPU? ??? ?? ?? ??, ? ??, ??? ? ?? ??, ?? ????? ?? ?? ???? ?? ???? ?????.

?? ??

?? ??? ? ??? ?? ?? ? ?? ? ?? ?? ??? ?????. ?? ?? ??? ???? ??? ?????.

1. CUDA ?? ???? ?????. ?? CUDA? ???? ???? ?? ?? ???? ?? ???? ?????. ?? ?? ????? ???? ?? ?? ???? ?????. ??? ????? ?? ?? ???? ????.
2. ?? ??? printf()? ??? ???. ?? ?? ?? ???? ?? threadIdx.x? blockIdx.x? ?? ??? ???. ???? ??? ?????? ? ?? ? ? ????
3. ???? threadIdx.y ?? threadIdx.z(?? blockIdx.y)? ?? ??? ???. (blockDim ? gridDim? ???????). ? ?? ??? ?????? 0? ?? ?? ?? ????? ??? ?? ???(dim? ?? 1)?
4. ??? ?? GPU? ???? ? ?? ?? add_grid.cu? ??? ???. K80 ???? ??? ? ???, ????? ? ??? ?????? (??: ???? ??? ?????? ??? CUDA 8 ?? ??? API? ?? ?????.) ? ??? ?? ??? ??? CUDA ???? ?? ?? ??? ???? ?????.

?? ??

? ???? CUDA? ?? ??? ??????, ? ?? ?? ??? ??? ??? CUDA C++? ???? ? ??? ???? ????. ???? ??? ???? ?? ?? ??? ?? ???? ??? ??? ???.

? ???? ???? CUDA ????? ?? ??? ??? ?????, ???? ?? ?? ??? ???? ????? ???(?? ??? ?? ????/??? ?????):

• CUDA C++?? ?? ???? ???? ??
• CUDA C++?? ???? ??? ???? ??? ???? ??
• CUDA C++?? ??? ??? ????? ??
• CUDA C++?? ??? ??? ???? ??
• CUDA C++?? ??? ???? ????? ????? ??
• CUDA C++?? ?? ??? ????
• CUDA C++? ???? ?? ????
• CUDA C++? ?? ???, 1?
• CUDA C++? ?? ?? ??, 2?
• CUDA? ??? ??? ???? ?? ????

??, ?? ??? ??? CUDA Fortran ??? ???? CUDA Fortran? ?? ???? ?????.

Udacity? NVIDIA?? ???? CUDA ?????? ?? ??? ??? ???? ?? ????.

NVIDIA ??? ????? CUDA C++ ? ?? GPU ??? ??? ?? ??? ???? ??? ????? ????!

? ??? ????? ? ?? ?? ??? ????? NVIDIA DLI?? ?? ?? ???? CUDA ????? ??? ?????.

• ?? ? ???? ??? ?? ?? GPU ???, ?? ??? ????? ??, NVIDIA Nsight ??? ??? ????? ??, ?? ?? ??? ??, ??? ??????, 8?? ??? ??, DLI ??? ?? ??? ???? CUDA C/C++? ??? ?? ???? ??? ?????.
• ??? ?????? ?? CUDA ???? ??? ?? ???? ??? ?????.
• ? ?? ?? ? ?? CUDA ????? ??? NVIDIA DLI ?? ??? ????? ?? ??? ??? ?????.

?? ???

• DLI ??: ? ?? CUDA ??
• DLI ??: CUDA C/C++? ??? ?? ???? ??
• GTC ??: CUDA ???? ?? ??: ?? ???
• GTC ??: CUDA C++ ?????: CUDA C++ ?? ?????? ??? ?? ?? ??
• GTC ??: CUDA ????? ? ?? ??? ??
• NGC ????: CUDA