// program description:
// This program written in BACI simulates the studying and
// drinking coffee of students.
int amtOfStudents; // how many students there are
int mugsPerPot; // how many mugs each pot fills
int timesToFill; // how many times to fill pot in simulation
int potToFillNext; // which pot to fill next
int fillCount =0; // how many times has pot been filled const
int amtOfPots = 5; // how many pots are there
int mugsLeft[ amtOfPots ];
int gettingFilled[ amtOfPots ];
semaphore outputMutex; // one person can write to screen
semaphore potNeedsFilling; // signal when student should fill
semaphore potMutex; // only one should get the pot
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semaphore checkMutex; // for checking if coffee is left
semaphore filledPot; // for checking if pot has coffee
semaphore confirm; // for changing which pot to fill
// student who fills the coffee pot
void studentFiller() {
int potToFill;
// continue to fill as long as the user wanted
while ( 1 && fillCount < timesToFill ) {
// sleep until the pot needs filling and then wait on pot access
wait( potNeedsFilling );
potToFill = potToFillNext;
signal( confirm );
wait( potMutex );
mugsLeft[ potToFill ] = mugsPerPot; // fill up the pot
fillCount = fillCount + 1; // increment fill count
wait( outputMutex );
cout << "Pot " << potToFill << " filled" << endl;
signal( outputMutex );
gettingFilled[ potToFillNext ] = 0; // pot getting filled
signal( potMutex ); // release access to the pot
signal( filledPot ); // signify that the pot was filled
}
}
// normal studying student
void student( int id ) {
int i; // used in for loop
int temp;
// continue to drink coffee as long as the user wanted
while ( 1 && fillCount < timesToFill ) {
temp = -1;
// wait for access to the pot
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wait( potMutex );
// if the pot is empty and it is not currently getting filled
for ( i = 0; i < amtOfPots; i = i + 1 ) {
if ( mugsLeft[ i ] == 0 && gettingFilled[ i ] == 0 ) {
wait( outputMutex );
cout << "Student " << id << " had the pot filled" << endl;
signal( outputMutex );
gettingFilled[ i ] = 1; // show pot about to fill
potToFillNext = i;
signal( potNeedsFilling ); // wake up the pot filler
wait( confirm ); // ensure stnt has pot number
}
}
// release access to the pot
signal( potMutex );
// if the last filling ended up being the last one then break
if ( fillCount >= timesToFill ) {
signal( filledPot );
break;
}
// wait for access to the pot
wait( potMutex );
// as long as the pot is empty keep looping
do {
for ( i = 0; i < amtOfPots && temp == -1; i = i + 1 ) {
if ( mugsLeft[ i ] > 0 ) {
temp = i;
}
}
signal( potMutex ); // release access to the pot
if ( fillCount < timesToFill ) {
wait( filledPot ); // wait until pot has stuff in it
}
else {
signal( filledPot );
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break;
}
wait( potMutex ); // wait on the pot again
}
while ( mugsLeft[ temp ] == 0 );
// drink a mug of coffee
mugsLeft[ temp ] = mugsLeft[ temp ] - 1;
if ( mugsLeft[ temp ] != 0 ) {
signal( filledPot ); // check if pot empty for next guy
}
wait( outputMutex );
if ( fillCount < timesToFill ) {
cout << "Student " << id << " drank a cup of coffee" << endl;
}
signal( outputMutex );
// release access to the pot
signal( potMutex );
}
}
// main function
void main() {
int i; // used in for loop
initialsem( outputMutex, 1 ); // initialize output sempahore
initialsem( potNeedsFilling, 0 ); // does the pot need filling
initialsem( potMutex, 1 ); // access to the coffee pot
initialsem( checkMutex, 1 ); // for checking mugsLeft
initialsem( filledPot, 1 ); // is coffee left
initialsem( confirm, 1 ); // is coffee left
cout << "How many students should there be ( no more than 17 ): ";
cin >> amtOfStudents;
cout << "How many mugs should each pot of coffee fill: ";
cin >> mugsPerPot;
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cout << "How many times should the coffee pot be filled: ";
cin >> timesToFill;
// fill up all the pots before starting
for ( i = 0; i < amtOfPots; i = i + 1 ) {
mugsLeft[ i ] = mugsPerPot;
gettingFilled[ i ] = 0;
}
// begin the appropriate number of students
cobegin {
studentFiller();
for ( i = 0; i < amtOfStudents; i = i + 1 ) {
student( i );
}
}
cout << "Simulation Finished!" << endl;
}