📄 parallel_preorder.cpp
字号:
/* Copyright 2005-2007 Intel Corporation. All Rights Reserved. This file is part of Threading Building Blocks. Threading Building Blocks is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 2 as published by the Free Software Foundation. Threading Building Blocks is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with Threading Building Blocks; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA As a special exception, you may use this file as part of a free software library without restriction. Specifically, if other files instantiate templates or use macros or inline functions from this file, or you compile this file and link it with other files to produce an executable, this file does not by itself cause the resulting executable to be covered by the GNU General Public License. This exception does not however invalidate any other reasons why the executable file might be covered by the GNU General Public License.*//* Example program that shows how to use parallel_while to do parallel preorder traversal of a directed acyclic graph. */#include "tbb/parallel_while.h"#include "tbb/atomic.h"#include <vector>#include <algorithm>#include "Graph.h"//! Number of trials. Can be changed from command lineint ntrial = 50;class Body { tbb::parallel_while<Body>& my_while; public: Body( tbb::parallel_while<Body>& w ) : my_while(w) {}; //------------------------------------------------------------------------ // Following signatures required by parallel_while //------------------------------------------------------------------------ typedef Cell* argument_type; void operator()( Cell* c ) const { c->update(); // Restore ref_count in preparation for subsequent traversal. c->ref_count = ArityOfOp[c->op]; for( size_t k=0; k<c->successor.size(); ++k ) { Cell* successor = c->successor[k]; if( 0 == --(successor->ref_count) ) { my_while.add( successor ); } } }}; class Stream { size_t k; const std::vector<Cell*>& my_roots;public: Stream( const std::vector<Cell*>& root_set ) : my_roots(root_set), k(0) {} bool pop_if_present( Cell*& item ) { bool result = k<my_roots.size(); if( result ) item = my_roots[k++]; return result; }}; void ParallelPreorderTraversal( const std::vector<Cell*>& root_set ) { tbb::parallel_while<Body> w; Stream s(root_set); w.run(s,Body(w));}//------------------------------------------------------------------------// Test driver//------------------------------------------------------------------------#include <cctype>#include "tbb/task_scheduler_init.h"#include "tbb/tick_count.h"//! A closed range of int.struct IntRange { int low; int high; void set_from_string( const char* s ); IntRange( int low_, int high_ ) : low(low_), high(high_) {}};void IntRange::set_from_string( const char* s ) { char* end; high = low = strtol(s,&end,0); switch( *end ) { case ':': high = strtol(end+1,0,0); break; case '\0': break; default: printf("unexpected character = %c\n",*end); }}//! Number of threads to use.static IntRange NThread(1,4);//! If true, then at end wait for user to hit returnstatic bool PauseFlag = false;//! Displays usage messagevoid Usage(char * argv0) { fprintf(stderr, "Usage: %s [nthread [ntrials ['pause']]]\n", argv0); fprintf(stderr, "where nthread is a non-negative integer, or range of the form low:high [%d:%d]\n", NThread.low, NThread.high); fprintf(stderr, "ntrials is a positive integer. Default value is 50, reduce it (e.g. to 5) to shorten example run time\n"); fprintf(stderr, "The application waits for user to hit return if 'pause' is specified\n");}//! Parse the command line.static void ParseCommandLine( int argc, char* argv[] ) { int i = 1; if( i<argc && !isdigit(argv[i][0]) ) { // Command line is garbled. Usage(argv[0]); exit(1); } if( i<argc ) NThread.set_from_string(argv[i++]); if( i<argc && !isdigit(argv[i][0]) ) { // Command line is garbled. Usage(argv[0]); exit(1); } if (i<argc) { ntrial = strtol(argv[i++], 0, 0); } if (ntrial == 0) { // Command line is garbled. Usage(argv[0]); exit(1); } if (i<argc && strcmp( argv[i], "pause" )==0 ) { PauseFlag = true; }}int main( int argc, char* argv[] ) { ParseCommandLine(argc,argv); // Start scheduler with given number of threads. for( int p=NThread.low; p<=NThread.high; ++p ) { tbb::task_scheduler_init init(p); srand(2); tbb::tick_count::interval_t interval; size_t total_root_set_size = 0; for( int trial=0; trial<ntrial; ++trial ) { Graph g; g.create_random_dag(1000); std::vector<Cell*> root_set; g.get_root_set(root_set); total_root_set_size += root_set.size(); tbb::tick_count t0 = tbb::tick_count::now(); for( int i=0; i<10; ++i ) { ParallelPreorderTraversal(root_set); } tbb::tick_count t1 = tbb::tick_count::now(); interval += t1-t0; } printf("%g seconds using %d threads (average of %g nodes in root_set)\n",interval.seconds(),p,(double)total_root_set_size/ntrial); } if (PauseFlag) { printf ("Press return key to exit"); char c; scanf("%c", &c); } return 0;}⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -