用Peterson算法实现临界区的控制

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定义两个全局变量初始值为0，用两个线程分别完成加1减1操作，然后相加两全局变量，结果为0则正确

设计思路

利用Peterson算法，实现线程间的互斥。

boolean flag[2];//初值false int turn; do{

flag[i]:=true; turn=j;

while(flag[j] and turn=j);

临界区;

flag[i]=false;

剩余区;

}while(1);

i为线程自身的序号减去1，j为2减去该线程的序号。

当某一进程试图访问临界区时，若另一进程已在访问临界区，则该线程通过循环等待直至另一线程退出临界区方可执行。

#include <windows.h>#include <conio.h>#include <stdlib.h>#include <fstream.h>#include <stdio.h>#define INTE_PER_SEC  1000#define MAX_THREAD_NUM  64struct ThreadInfo{intserial;doubledelay;};volatile  int accnt1 = 0; /*  in the memory */volatile  int accnt2 = 0;void account( char* file);void acc(void* p);////////////////////////////////////////////////////////// main fuction////////////////////////////////////////////////////////int main( int agrc, char* argv[] ){char ch;while ( TRUE ){// Cleare screensystem( "cls" );// display prompt infoprintf("*********************************************\n");printf("       1.Start test\n");printf("       2.Exit to Windows\n");printf("*********************************************\n");printf("Input your choice(1or2): ");// if the number inputed is error, retry!do{ch = (char)_getch(); }while( ch != '1' && ch != '2');system ( "cls" );if ( ch == '1')account("sm6.dat");else if ( ch == '2')return 0;printf("\nPress any key to finish this Program. \nThank you test this Proggram!\n");_getch();} //end while} //end mainvoid account( char* file){DWORD n_thread = 0;DWORD thread_ID;DWORD wait_for_all;// Tread Object ArrayHANDLE h_Thread[MAX_THREAD_NUM];ThreadInfo  thread_info[MAX_THREAD_NUM];ifstream  inFile;inFile.open(file);//open fileprintf( "Now, We begin to read thread Information to thread_info array \n\n" );while ( inFile ){// read every thread infoinFile>>thread_info[n_thread].serial;inFile>>thread_info[n_thread++].delay;inFile.get();} //end while// Create all threadfor( int i = 0; i < (int)(n_thread); i++){// Create a thread    h_Thread[i] = CreateThread( NULL, 0, (LPTHREAD_START_ROUTINE)(acc), &thread_info[i], 0, &thread_ID);} //end for// Create thread// waiting all thread will been finishedwait_for_all = WaitForMultipleObjects(n_thread,h_Thread,TRUE, -1);printf("All threads have finished Operating.\n");}// end accountvoid acc(void* p){DWORD m_delay;int m_serial;int rand_num, accnt,counter = 0;;//get info froam param_serial = ((ThreadInfo*) (p)) -> serial;m_delay  = (DWORD) (((ThreadInfo*)(p)) -> delay*INTE_PER_SEC);boolean flag[2];flag[0]=flag[1]=false;int turn,a;srand( (unsigned)((ThreadInfo*)(p)) -> delay );do {printf("I am thread  %d , I am doing  %05dth step\n",m_serial,counter);rand_num = rand();printf("rand_num =  %05d \n",rand_num);//Sleep(m_delay);//begin critical_sectionflag[m_serial-1]=true;a=2-m_serial;turn=a;while(flag[a]&&turn==a);accnt1 = accnt1 - rand_num;//Sleep(m_delay);accnt2 = accnt2 + rand_num;accnt = accnt1 + accnt2; /*critical section*/ ;    flag[m_serial-1]=false;printf("Now accnt1+accnt2 =  %05d\n",accnt);Sleep(10*m_serial+700);  //wait a moment//critical_section  endcounter++;} while ( (accnt == 0) && (counter<10)); printf("Now accnt1+accnt2 =  %05d\n",accnt);} //end acc

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