Ядро CUDA перестает работать при использовании функции синхронизации сетки совместных групп ()
Я пытался реализовать некоторые ядра cuda, используя функцию кооперативных групп, когда обнаружил, что ядро вообще ничего не делает. Я свел это к небольшому примеру, который можно увидеть ниже. Как только я позвоню
sync()функция ядра cuda больше не работает. Я уже убедился, что вычислительные возможности моих графических процессоров (GTX 1070 Ti) достаточно высоки, а также добавил соответствующие переключатели (-rdc, -gencode) в nvcc.
Команда компиляции:
nvcc -o kernel.bin kernel.cu -I /nix/store/lxyjz3j1qbrf9hw0nnsdang3gk2a8wpp-cudatoolkit-11.0.3/include/ -ldir /nix/store/lxyjz3j1qbrf9hw0nnsdang3gk2a8wpp-cudatoolkit-11.0.3/nvvm/libdevice/ -L /nix/store/lxyjz3j1qbrf9hw0nnsdang3gk2a8wpp-cudatoolkit-11.0.3/lib/ -L /nix/store/sdjf499xfbykmr3lsyd7084krjxr3mfx-cudatoolkit-11.0.3-lib/lib/ --dont-use-profile -G --std=c++11 -rdc=true -gencode=arch=compute_60,code=sm_60 -lcudadevrt
Ядро без синхронизации()
#include <iostream>
#include <cooperative_groups.h>
using namespace std;
__global__ void coopkernel(float* buffer)
{
int id = threadIdx.x + blockDim.x * blockIdx.x;
auto g = cooperative_groups::this_grid();
buffer[id] = 13;
// g.sync();
}
Вывод (как и ожидалось)
Runtime Version: 11000
Driver Version: 11010
Return Code from Kernel: 0
Explanation: no error
13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13
Пример ошибки ядра с sync()
#include <iostream>
#include <cooperative_groups.h>
using namespace std;
__global__ void coopkernel(float* buffer)
{
int id = threadIdx.x + blockDim.x * threadIdx.y + blockIdx.x*(blockDim.x*blockDim.y);
auto g = cooperative_groups::this_grid();
buffer[id] = 13;
g.sync();
}
Выход (все равно 0)
Runtime Version: 11000
Driver Version: 11010
Return Code from Kernel: 0
Explanation: no error
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 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Полный код:
#include <iostream>
#include <cooperative_groups.h>
using namespace std;
__global__ void coopkernel(float* buffer)
{
int id = threadIdx.x + blockDim.x * blockIdx.x;
auto g = cooperative_groups::this_grid();
buffer[id] = 13;
// g.sync();
}
int main()
{
// Grid with 2 Block in x direction
dim3 dimGrid(2, 1, 1);
// 1024 Threads per Block
dim3 dimBlock(1024, 1, 1);
int run_version, driver_version;
cudaRuntimeGetVersion(&run_version);
cudaDriverGetVersion(&driver_version);
std::cout << "Runtime Version: ";
std::cout << run_version;
std::cout << "\nDriver Version: ";
std::cout << driver_version;
// just an arbitrary buffer
int bytes_buffer = 2048 * sizeof(float);
float *host_buffer = (float*)malloc(bytes_buffer);
// initialize to 0
memset(host_buffer, 0, bytes_buffer);
// Device pointer to buffer
float *d_buffer;
cudaMalloc(&d_buffer, bytes_buffer);
cudaMemcpy(d_buffer, host_buffer, bytes_buffer, cudaMemcpyHostToDevice);
// Launch kernel
coopkernel <<<dimGrid, dimBlock>>> (d_buffer);
std::cout << "\nReturn Code from Kernel: ";
std::cout << cudaPeekAtLastError();
std::cout << "\nExplanation: ";
std::cout << cudaGetErrorString(cudaGetLastError());
std::cout << "\n";
cudaMemcpy(host_buffer, d_buffer, bytes_buffer, cudaMemcpyDeviceToHost);
// Print the result
for(int i=0; i < 2048; i++)
{
std::cout << host_buffer[i];
std::cout << ", ";
}
cudaFree(d_buffer);
return 0;
}
Вопросы
Почему это происходит?
Как это исправить?
Или какие-нибудь советы по устранению неполадок? Очень странно, что ядро возвращает успех через
cudaGetLastError()хотя ничего не делал.
PS выход nvidia-smi
nvidia-smi
Tue Dec 8 18:29:46 2020
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 455.38 Driver Version: 455.38 CUDA Version: 11.1 |
|-------------------------------+----------------------+----------------------+
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
| | | MIG M. |
|===============================+======================+======================|
| 0 GeForce GTX 107... Off | 00000000:2A:00.0 On | N/A |
| 0% 51C P0 34W / 180W | 1121MiB / 8116MiB | 1% Default |
| | | N/A |
+-------------------------------+----------------------+----------------------+
+-----------------------------------------------------------------------------+
| Processes: |
| GPU GI CI PID Type Process name GPU Memory |
| ID ID Usage |
|=============================================================================|
| 0 N/A N/A 1209 G ...-xorg-server-1.20.8/bin/X 613MiB |
| 0 N/A N/A 1728 G ...nt-system/sw/bin/kwin_x11 256MiB |
| 0 N/A N/A 1772 G ...ce-5.18.5/bin/plasmashell 119MiB |
| 0 N/A N/A 1868 G ...AAAAAAAA== --shared-files 76MiB |
| 0 N/A N/A 2772 G ...AAAAAAAAA= --shared-files 48MiB |
+-----------------------------------------------------------------------------+