gpufilter
GPU-Efficient Recursive Filtering and Summed-Area Tables
|
This is an example of how to use the alg5() function in the GPU and the r() function in the CPU, as well as the gpufilter::scoped_timer_stop class.
#include <ctime> #include <cstdlib> #include <iostream> #include <iomanip> #include <timer.h> #include <cpuground.h> #include <gpufilter.h> #include <util.h> // Check computation void check_reference( const float *ref, const float *res, const int& ne, float& me, float& mre ) { mre = me = (float)0; for (int i = 0; i < ne; i++) { float a = (float)(res[i]) - ref[i]; if( a < (float)0 ) a = -a; if( ref[i] != (float)0 ) { float r = (ref[i] < (float)0) ? -ref[i] : ref[i]; float b = a / r; mre = b > mre ? b : mre; } me = a > me ? a : me; } } // Main int main(int argc, char *argv[]) { const int in_w = 1024, in_h = 1024; const float b0 = 0.482305, a1 = -0.517695; std::cout << "[r2] Generating random input image (" << in_w << "x" << in_h << ") ... " << std::flush; float *in_cpu = new float[in_w*in_h]; float *in_gpu = new float[in_w*in_h]; srand(time(0)); for (int i = 0; i < in_w*in_h; ++i) in_gpu[i] = in_cpu[i] = rand() / (float)RAND_MAX; std::cout << "done!\n[r2] Recursive filter: y_i = b0 * x_i - a1 * " << "y_{i-1}\n[r2] Considering forward and reverse on rows " << "and columns\n[r2] Feedforward and feedback coefficients " << "are: b0 = " << b0 << " ; a1 = " << a1 << "\n" << "[r2] CPU Computing first-order recursive filtering with " << "zero-border ... " << std::flush; std::cout << std::fixed << std::setprecision(2); { gpufilter::scoped_timer_stop sts( gpufilter::timers.cpu_add("CPU") ); gpufilter::r( in_cpu, in_w, in_h, b0, a1 ); std::cout << "done!\n[r2] CPU Timing: " << sts.elapsed()*1000 << " ms\n"; } std::cout << "[r2] GPU Computing first-order recursive filtering with " << "zero-border ... " << std::flush; { gpufilter::scoped_timer_stop sts( gpufilter::timers.gpu_add("GPU") ); gpufilter::alg5( in_gpu, in_w, in_h, b0, a1 ); std::cout << "done!\n[r2] GPU Timing: " << sts.elapsed()*1000 << " ms\n"; } std::cout << "[r2] GPU Timing includes memory transfers from and to " << "the CPU\n" << "[r2] Checking GPU result against CPU reference\n"; float me, mre; check_reference( in_cpu, in_gpu, in_w*in_h, me, mre ); std::cout << std::resetiosflags( std::ios_base::floatfield ); std::cout << "[r2] Maximum relative error: " << mre << " ; Maximum error: " << me << "\n"; delete [] in_cpu; delete [] in_gpu; return 0; }