一、管程來解決生産者/消費者問題
1)
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Struct Monitor
{
condition NF,NE;
int Buffer[n];
int k = 0,t = 0,count = 0;
define Add(int),Remove(int);
use wait(),signal(),check(),release();
void init() //初始化局部變量和條件變量
{
count = 0;k = 0;t = 0;NF = 0;NE = 0;
}
vodi Add(int i)
{
check();
if(count ==n) wait(NF);
Buffer[k] = i;
k = (k+1)%n;
count++;
signal(NE);
release();
}
void Remove(int &i)
{
check();
if(count == 0)wait(NE);
i = Buffer[t];
t = (t+1)%n;
count–;
signal(NF);
release();
}
}
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process producteri()//i = 1,2…,m
{
int x;
x = 生産一個産品(整數)
Add(x);
}
process consumerj()//j = 1,2,…,r
{
int x;
Remove(x);
消費該産品(整數);
}
二、用管程來解決優先寫着的讀者/寫着問題
優先寫者的讀者/寫着問題要求是:
①讀者共享;
②寫着互斥;
③有讀者在讀,寫着不可寫;
④寫着在寫,讀者不可讀;
⑤當讀者在讀時,寫着提出寫的要求,後面的讀者就不允許進入讀檔案;
⑥當裡面的讀者讀完時,由寫着進入寫;
⑦當寫着寫完後,優先喚醒等待的寫着,如果沒有寫着等待,才喚醒等待的讀者進行讀;
1)
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struct Monitor
{
condition RR,WW;
int ReaderCnt,WriterCnt;
define StartRead,EndRead,StartWrite,EndWrite;
use wait,signal,check,release;
void StartRead()
{
check();
if(WriterCnt>0)wait(RR);
ReaderCnt++;
signal(RR);
release();
}
void EndRead()
{
check();
ReaderCnt–;
if(ReaderCnt == 0)signal(WW);
release();
}
void StartWrite()
{
check();
WriterCnt++;
if(ReadCnt>0 || WriterCnt>1)wait(WW);
release();
}
void EndWrite()
{
check();
WriterCnt–;
if(WriterCnt>0)signal(WW);
else
signal(RR);
release();
}
void init()
{
ReaderCnt=0;WriterCnt=0;RR=0;WW=0;
}
}
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process reader()
{
ReadWriter.StartRead();
讀檔案;
ReadWriter.EndRead();
}
process writer()
{
ReadWriter.StartWrite();
寫檔案;
ReadWriter.EndWrite();
}