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/* Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of NVIDIA CORPORATION nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <helper_cuda.h>
#include <helper_string.h>
#include <cstdio>
#include <cstdlib>
#include <iostream>
////////////////////////////////////////////////////////////////////////////////
// Variable on the GPU used to generate unique identifiers of blocks.
////////////////////////////////////////////////////////////////////////////////
__device__ int g_uids = 0;
////////////////////////////////////////////////////////////////////////////////
// Print a simple message to signal the block which is currently executing.
////////////////////////////////////////////////////////////////////////////////
__device__ void print_info(int depth, int thread, int uid, int parent_uid) {
if (threadIdx.x == 0) {
if (depth == 0)
printf("BLOCK %d launched by the host\n", uid);
else {
char buffer[32];
for (int i = 0; i < depth; ++i) {
buffer[3 * i + 0] = '|';
buffer[3 * i + 1] = ' ';
buffer[3 * i + 2] = ' ';
}
buffer[3 * depth] = '\0';
printf("%sBLOCK %d launched by thread %d of block %d\n", buffer, uid,
thread, parent_uid);
}
}
__syncthreads();
}
////////////////////////////////////////////////////////////////////////////////
// The kernel using CUDA dynamic parallelism.
//
// It generates a unique identifier for each block. Prints the information
// about that block. Finally, if the 'max_depth' has not been reached, the
// block launches new blocks directly from the GPU.
////////////////////////////////////////////////////////////////////////////////
__global__ void cdp_kernel(int max_depth, int depth, int thread,
int parent_uid) {
// We create a unique ID per block. Thread 0 does that and shares the value
// with the other threads.
__shared__ int s_uid;
if (threadIdx.x == 0) {
s_uid = atomicAdd(&g_uids, 1);
}
__syncthreads();
// We print the ID of the block and information about its parent.
print_info(depth, thread, s_uid, parent_uid);
// We launch new blocks if we haven't reached the max_depth yet.
if (++depth >= max_depth) {
return;
}
cdp_kernel<<<gridDim.x, blockDim.x>>>(max_depth, depth, threadIdx.x, s_uid);
}
////////////////////////////////////////////////////////////////////////////////
// Main entry point.
////////////////////////////////////////////////////////////////////////////////
int main(int argc, char **argv) {
printf("starting Simple Print (CUDA Dynamic Parallelism)\n");
// Parse a few command-line arguments.
int max_depth = 2;
if (checkCmdLineFlag(argc, (const char **)argv, "help") ||
checkCmdLineFlag(argc, (const char **)argv, "h")) {
printf(
"Usage: %s depth=<max_depth>\t(where max_depth is a value between 1 "
"and 8).\n",
argv[0]);
exit(EXIT_SUCCESS);
}
if (checkCmdLineFlag(argc, (const char **)argv, "depth")) {
max_depth = getCmdLineArgumentInt(argc, (const char **)argv, "depth");
if (max_depth < 1 || max_depth > 8) {
printf("depth parameter has to be between 1 and 8\n");
exit(EXIT_FAILURE);
}
}
// Find/set the device.
int device = -1;
cudaDeviceProp deviceProp;
device = findCudaDevice(argc, (const char **)argv);
checkCudaErrors(cudaGetDeviceProperties(&deviceProp, device));
if (!(deviceProp.major > 3 ||
(deviceProp.major == 3 && deviceProp.minor >= 5))) {
printf("GPU %d - %s does not support CUDA Dynamic Parallelism\n Exiting.",
device, deviceProp.name);
exit(EXIT_WAIVED);
}
// Print a message describing what the sample does.
printf(
"*********************************************************************"
"******\n");
printf(
"The CPU launches 2 blocks of 2 threads each. On the device each thread "
"will\n");
printf(
"launch 2 blocks of 2 threads each. The GPU we will do that "
"recursively\n");
printf("until it reaches max_depth=%d\n\n", max_depth);
printf("In total 2");
int num_blocks = 2, sum = 2;
for (int i = 1; i < max_depth; ++i) {
num_blocks *= 4;
printf("+%d", num_blocks);
sum += num_blocks;
}
printf("=%d blocks are launched!!! (%d from the GPU)\n", sum, sum - 2);
printf(
"************************************************************************"
"***\n\n");
// Launch the kernel from the CPU.
printf("Launching cdp_kernel() with CUDA Dynamic Parallelism:\n\n");
cdp_kernel<<<2, 2>>>(max_depth, 0, 0, -1);
checkCudaErrors(cudaGetLastError());
// Finalize.
checkCudaErrors(cudaDeviceSynchronize());
exit(EXIT_SUCCESS);
}
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