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 #include <functional> #include <iostream> #include <string> #include <vector>
#include <cuda_runtime.h>
#define CHECK_CUDA_ERROR(val) check((val), #val, __FILE__, __LINE__) void check(cudaError_t err, const char* const func, const char* const file, const int line) { if (err != cudaSuccess) { std::cerr << "CUDA Runtime Error at: " << file << ":" << line << std::endl; std::cerr << cudaGetErrorString(err) << " " << func << std::endl; std::exit(EXIT_FAILURE); } }
#define CHECK_LAST_CUDA_ERROR() checkLast(__FILE__, __LINE__) void checkLast(const char* const file, const int line) { cudaError_t const err{cudaGetLastError()}; if (err != cudaSuccess) { std::cerr << "CUDA Runtime Error at: " << file << ":" << line << std::endl; std::cerr << cudaGetErrorString(err) << std::endl; std::exit(EXIT_FAILURE); } }
template <class T> float measure_performance(std::function<T(cudaStream_t)> bound_function, cudaStream_t stream, unsigned int num_repeats = 100, unsigned int num_warmups = 100) { cudaEvent_t start, stop; float time;
CHECK_CUDA_ERROR(cudaEventCreate(&start)); CHECK_CUDA_ERROR(cudaEventCreate(&stop));
for (unsigned int i{0}; i < num_warmups; ++i) { bound_function(stream); }
CHECK_CUDA_ERROR(cudaStreamSynchronize(stream));
CHECK_CUDA_ERROR(cudaEventRecord(start, stream)); for (unsigned int i{0}; i < num_repeats; ++i) { bound_function(stream); } CHECK_CUDA_ERROR(cudaEventRecord(stop, stream)); CHECK_CUDA_ERROR(cudaEventSynchronize(stop)); CHECK_LAST_CUDA_ERROR(); CHECK_CUDA_ERROR(cudaEventElapsedTime(&time, start, stop)); CHECK_CUDA_ERROR(cudaEventDestroy(start)); CHECK_CUDA_ERROR(cudaEventDestroy(stop));
float const latency{time / num_repeats};
return latency; }
constexpr unsigned int N{64U * 1024U / sizeof(int)}; __constant__ int const_values[N];
constexpr unsigned int magic_number{1357U};
enum struct AccessPattern { OneAccessPerBlock, OneAccessPerWarp, OneAccessPerThread, PseudoRandom };
void add_constant_cpu(int* sums, int const* inputs, int const* values, unsigned int num_sums, unsigned int num_values, unsigned int block_size, AccessPattern access_pattern) { for (unsigned int i{0U}; i < num_sums; ++i) { unsigned int const block_id{i / block_size}; unsigned int const thread_id{i % block_size}; unsigned int const warp_id{thread_id / 32U}; unsigned int index{0U};
switch (access_pattern) { case AccessPattern::OneAccessPerBlock: index = block_id % num_values; break; case AccessPattern::OneAccessPerWarp: index = warp_id % num_values; break; case AccessPattern::OneAccessPerThread: index = thread_id % num_values; break; case AccessPattern::PseudoRandom: index = (thread_id * magic_number) % num_values; break; }
sums[i] = inputs[i] + values[index]; } }
__global__ void add_constant_global_memory( int* sums, int const* inputs, int const* values, unsigned int num_sums, unsigned int num_values, AccessPattern access_pattern = AccessPattern::OneAccessPerBlock) { unsigned int const i{blockIdx.x * blockDim.x + threadIdx.x}; unsigned int const block_id{blockIdx.x}; unsigned int const thread_id{threadIdx.x}; unsigned int const warp_id{threadIdx.x / warpSize}; unsigned int index{0U};
switch (access_pattern) { case AccessPattern::OneAccessPerBlock: index = block_id % num_values; break; case AccessPattern::OneAccessPerWarp: index = warp_id % num_values; break; case AccessPattern::OneAccessPerThread: index = thread_id % num_values; break; case AccessPattern::PseudoRandom: index = (thread_id * magic_number) % num_values; break; }
if (i < num_sums) { sums[i] = inputs[i] + values[index]; } }
void launch_add_constant_global_memory(int* sums, int const* inputs, int const* values, unsigned int num_sums, unsigned int num_values, unsigned int block_size, AccessPattern access_pattern, cudaStream_t stream) { add_constant_global_memory<<<(num_sums + block_size  1) / block_size, block_size, 0, stream>>>( sums, inputs, values, num_sums, num_values, access_pattern); CHECK_LAST_CUDA_ERROR(); }
__global__ void add_constant_constant_memory(int* sums, int const* inputs, unsigned int num_sums, AccessPattern access_pattern) { unsigned int const i{blockIdx.x * blockDim.x + threadIdx.x}; unsigned int const block_id{blockIdx.x}; unsigned int const thread_id{threadIdx.x}; unsigned int const warp_id{threadIdx.x / warpSize}; unsigned int index{0U};
switch (access_pattern) { case AccessPattern::OneAccessPerBlock: index = block_id % N; break; case AccessPattern::OneAccessPerWarp: index = warp_id % N; break; case AccessPattern::OneAccessPerThread: index = thread_id % N; break; case AccessPattern::PseudoRandom: index = (thread_id * magic_number) % N; break; }
if (i < num_sums) { sums[i] = inputs[i] + const_values[index]; } }
void launch_add_constant_constant_memory(int* sums, int const* inputs, unsigned int num_sums, unsigned int block_size, AccessPattern access_pattern, cudaStream_t stream) { add_constant_constant_memory<<<(num_sums + block_size  1) / block_size, block_size, 0, stream>>>( sums, inputs, num_sums, access_pattern); CHECK_LAST_CUDA_ERROR(); }
void parse_args(int argc, char** argv, AccessPattern& access_pattern, unsigned int& block_size, unsigned int& num_sums) { if (argc < 4) { std::cerr << "Usage: " << argv[0] << " <access pattern> <block size> <number of sums>" << std::endl; std::exit(EXIT_FAILURE); }
std::string const access_pattern_str{argv[1]}; if (access_pattern_str == "one_access_per_block") { access_pattern = AccessPattern::OneAccessPerBlock; } else if (access_pattern_str == "one_access_per_warp") { access_pattern = AccessPattern::OneAccessPerWarp; } else if (access_pattern_str == "one_access_per_thread") { access_pattern = AccessPattern::OneAccessPerThread; } else if (access_pattern_str == "pseudo_random") { access_pattern = AccessPattern::PseudoRandom; } else { std::cerr << "Invalid access pattern: " << access_pattern_str << std::endl; std::exit(EXIT_FAILURE); }
block_size = std::stoi(argv[2]); num_sums = std::stoi(argv[3]); }
int main(int argc, char** argv) { constexpr unsigned int num_warmups{100U}; constexpr unsigned int num_repeats{100U};
AccessPattern access_pattern{AccessPattern::OneAccessPerBlock}; unsigned int block_size{1024U}; unsigned int num_sums{12800000U}; parse_args(argc, argv, access_pattern, block_size, num_sums);
cudaStream_t stream; CHECK_CUDA_ERROR(cudaStreamCreate(&stream));
int h_values[N]; for (unsigned int i{0U}; i < N; ++i) { h_values[i] = i; } int* d_values; CHECK_CUDA_ERROR(cudaMallocAsync(&d_values, N * sizeof(int), stream)); CHECK_CUDA_ERROR(cudaMemcpyAsync(d_values, h_values, N * sizeof(int), cudaMemcpyHostToDevice, stream)); CHECK_CUDA_ERROR(cudaMemcpyToSymbolAsync(const_values, h_values, N * sizeof(int), 0, cudaMemcpyHostToDevice, stream));
std::vector<int> inputs(num_sums, 0); int* h_inputs{inputs.data()}; int* d_inputs_for_constant; int* d_inputs_for_global; CHECK_CUDA_ERROR(cudaMallocAsync(&d_inputs_for_constant, num_sums * sizeof(int), stream)); CHECK_CUDA_ERROR( cudaMallocAsync(&d_inputs_for_global, num_sums * sizeof(int), stream)); CHECK_CUDA_ERROR(cudaMemcpyAsync(d_inputs_for_constant, h_inputs, num_sums * sizeof(int), cudaMemcpyHostToDevice, stream)); CHECK_CUDA_ERROR(cudaMemcpyAsync(d_inputs_for_global, h_inputs, num_sums * sizeof(int), cudaMemcpyHostToDevice, stream));
std::vector<int> reference_sums(num_sums, 0); std::vector<int> sums_from_constant(num_sums, 1); std::vector<int> sums_from_global(num_sums, 2);
int* h_reference_sums{reference_sums.data()}; int* h_sums_from_constant{sums_from_constant.data()}; int* h_sums_from_global{sums_from_global.data()};
int* d_sums_from_constant; int* d_sums_from_global; CHECK_CUDA_ERROR( cudaMallocAsync(&d_sums_from_constant, num_sums * sizeof(int), stream)); CHECK_CUDA_ERROR( cudaMallocAsync(&d_sums_from_global, num_sums * sizeof(int), stream));
CHECK_CUDA_ERROR(cudaStreamSynchronize(stream));
add_constant_cpu(h_reference_sums, h_inputs, h_values, num_sums, N, block_size, access_pattern); launch_add_constant_global_memory(d_sums_from_global, d_inputs_for_global, d_values, num_sums, N, block_size, access_pattern, stream); launch_add_constant_constant_memory(d_sums_from_constant, d_inputs_for_constant, num_sums, block_size, access_pattern, stream);
CHECK_CUDA_ERROR(cudaMemcpyAsync(h_sums_from_constant, d_sums_from_constant, num_sums * sizeof(int), cudaMemcpyDeviceToHost, stream)); CHECK_CUDA_ERROR(cudaMemcpyAsync(h_sums_from_global, d_sums_from_global, num_sums * sizeof(int), cudaMemcpyDeviceToHost, stream));
CHECK_CUDA_ERROR(cudaStreamSynchronize(stream));
for (unsigned int i{0U}; i < num_sums; ++i) { if (h_reference_sums[i] != h_sums_from_constant[i]) { std::cerr << "Error at index " << i << " for constant memory." << std::endl; std::exit(EXIT_FAILURE); } if (h_reference_sums[i] != h_sums_from_global[i]) { std::cerr << "Error at index " << i << " for global memory." << std::endl; std::exit(EXIT_FAILURE); } }
std::function<void(cudaStream_t)> bound_function_constant_memory{ std::bind(launch_add_constant_constant_memory, d_sums_from_constant, d_inputs_for_constant, num_sums, block_size, access_pattern, std::placeholders::_1)}; std::function<void(cudaStream_t)> bound_function_global_memory{ std::bind(launch_add_constant_global_memory, d_sums_from_global, d_inputs_for_global, d_values, num_sums, N, block_size, access_pattern, std::placeholders::_1)}; float const latency_constant_memory{measure_performance( bound_function_constant_memory, stream, num_repeats, num_warmups)}; float const latency_global_memory{measure_performance( bound_function_global_memory, stream, num_repeats, num_warmups)}; std::cout << "Latency for Add using constant memory: " << latency_constant_memory << " ms" << std::endl; std::cout << "Latency for Add using global memory: " << latency_global_memory << " ms" << std::endl;
CHECK_CUDA_ERROR(cudaStreamDestroy(stream)); CHECK_CUDA_ERROR(cudaFree(d_values)); CHECK_CUDA_ERROR(cudaFree(d_inputs_for_constant)); CHECK_CUDA_ERROR(cudaFree(d_inputs_for_global)); CHECK_CUDA_ERROR(cudaFree(d_sums_from_constant)); CHECK_CUDA_ERROR(cudaFree(d_sums_from_global));
return 0; }
