int WorkFunc( int q, void *p ) {
int i;
int array[5];
PI_Read( chans[q], "%5d", array );
for ( i = 0; i < 5; i++ ) {
array[i] = array[i] + q;
}
PI_Write( chans_out[q], "%5d", array );
return 0;
}
/*
Performs all the work in the parallel version of this program. Is not run in serial version of this program (when workerCount == 0).
- Loops accepting data from PI_Main until END_OF_DATA message is recieved.
- Each time data is recieved the data is processed, the results appended to the variable 'pallindromes' and then this worker tells PI_Main it is ready for more data.
- When END_OF_DATA message is recieved, this worker sends PI_Main the contents of the variable 'pallindromes'.
*/
int workerFunc( int index, void* arg2 )
{
int pallindromesCount = 0;// How many pallindromes have been found so far
int maxPallindromes = 32; // The maximum number of pallindromes that can be held by this worker. This will grow dynamically to keep up as the worker finds more and more pallindromes.
int startingLine = 0; // The starting line of the data sent from PI_Main. Data from PI_Main is assumed to be a continous set of lines from the input file.
int dataLength = 0; // The number of chars (+ 1 for '\0') contained in the last data sent from PI_Main.
int lineIndex = 0; // The current index of a temporary string, used to parse the data from PI_Main. The string this indexes is sent to function 'LineIsPalindrome()'.
int curLine; // The running counter of what line we are on in the file. 'curLine' starts at startingLine, and is incremented everytime a '\n' is found in variable 'data' from PI_Main.
int i; // Generic iterator variable, used to loop through the data sent from PI_Main.
char line[MAX_LINE_LENGTH]; // A single line from the input file. Parsed out of the data sent from PI_Main in the variable 'data'.
char *pallindromes; // The output from this worker, 'pallindromes' will be returned to PI_Main when this workers recieves END_OF_DATA as a line number.
// Simply a list of all the lines in the input file that are pallindromes, seperated by newlines.
char *data = NULL; // The data sent from PI_Main, LINES_BEFORE_SENDING number of lines or less. This is a continous string, each line must be parsed out by looking for '\n's.
// Malloc pallindromes to a default starting size
pallindromes = (char *)malloc(sizeof(char) * maxPallindromes * MAX_OUTPUT_LINE_LENGTH);
while(1){
// Tell PI_Main this worker is ready for data.
PI_Write( result[index], "%c", READY_FOR_DATA);
// Wait until PI_Main sends this worker something.
PI_Read( toWorker[index], "%d", &startingLine);
// If PI_Main sends us the END_OF_DATA signal, we're done, otherwise we should work on the data recieved.
if(startingLine == END_OF_DATA){
break;
}
// If PI_Main didn't send us END_OF_DATA, then PI_MAIN must have data for us to work on.
PI_Read( toWorker[index], "%^s", &dataLength, &data );
// Once we have the data, initalize the workers line counter.
curLine = startingLine;
// Go through each char of the data recieved in order to parse it.
for(i = 0; i < dataLength; i++){
// Copy the data from PI_Main into a single line.
line[lineIndex] = data[i];
lineIndex++;
// If we encounter a char that represents the end of a line, we have a line, and we should figure out if it is a pallindrome.
if(data[i] == '\n' || data[i] == '\0'){
line[lineIndex - 1] = '\0';// Cap the line, so it becomes a proper C style string.
if(LineIsPalindrome(line)){
if(pallindromesCount >= maxPallindromes){ // If we've run out of space to store line numbers of lines that are pallindromes,
maxPallindromes = maxPallindromes * 2; // have this worker allocate more space. Double the amount of space we allocate each time in an attempt to
pallindromes = (char *)realloc(pallindromes, sizeof(char) * maxPallindromes * MAX_OUTPUT_LINE_LENGTH); // balance performance and memory usage.
if(pallindromes == NULL){
ExitFailure("Error reallocing...", __FILE__, __LINE__);
}
}
// Save the line number to our workers output string, (if it is a pallindrome), and increment the number of pallindromes we've found.
sprintf(&(pallindromes[pallindromesCount * MAX_OUTPUT_LINE_LENGTH]), "%010d\n", curLine);
pallindromesCount++;
}
// Prepare to continue reading the data sent from PI_Main.
curLine++;
line[0] = '\0';
lineIndex = 0;
}
}
free(data);
}
printf(">> Worker %d recieived end of data message\n\n", index);
// Send PI_Main the results of this workers work.
PI_Write( result[index], "%^s", strlen(pallindromes) + 1, pallindromes);
free(pallindromes);
return 0;
}
/*
Part of the parallel verison of this program. This function acts as 'PI_Main' in the master/worker configuration.
- Loops while there is still data in the input file, and sends a chunck of data off to a worker,
as soon a chunk is read in from the input file. (Chunk size is defined by LINES_BEFORE_SENDING).
- Once the end of the input file is reached, sends a signal to every worker that there is no more data left.
- Once all workers have recieved the END_OF_DATA signal, this function collects the data from each worker one by one,
writes said data to the output file right away.
*/
void Parallel(FILE *inputFile, FILE *outputFile, int workerCount){
printf(">> STARTING PARALLEL...\n");
char buffer[LINES_BEFORE_SENDING * MAX_LINE_LENGTH]; // Buffer which is the maximum size we can send to a worker in a single chunk.
char *workerResult = NULL; // The data gotten back from a worker, after the worker is told they are done. The output of this program.
char curChar = ' '; // The current char read in from the input file.
char signal = ' '; // Char recieved from worker, to tell PI_Main (this function) that the sending worker is ready for more data.
int workerResultLength = 0; // The length of the result from the worker.
int linesSinceSending = 0; // The number of lines we've read in from the input file. Resets to 0 everytime we send a chunk of data/lines to a worker.
int nextChannel = 0; // The next channel that is able to accept data from PI_Main (this function).
int bufferPos = 0; // The number of chars currently in the line buffer, once we find a newline this is reset to zero.
int lineNum = 1; // The current line number we are on in the input file.
int i; //Generic iterator, used to go through each channel to tell workers they are done, and then collect thier data.
while(curChar != EOF){
curChar = fgetc(inputFile);
// Read the file in char by char, and construct the file into lines, one line at a time.
if(curChar != '\0'){// Ignore null terminators in the buffer.
buffer[bufferPos] = curChar;
bufferPos++;
}
// When we find a line, increment the number of lines we've found since last time we sent a chunk of lines.
if(curChar == '\n' || curChar == '\0' || curChar == EOF){
linesSinceSending++;
// If the threshold number of lines is reached, send the chunk of lines to the next available worker.
if(linesSinceSending >= LINES_BEFORE_SENDING || curChar == EOF){
buffer[bufferPos-1] = '\0';
// Find the next available worker, and read their ready message.
nextChannel = PI_Select(fromWorkerBundle);
PI_Read(result[nextChannel], "%c", &signal);
// Send them the line number we started at since last time a chunk of lines was sent, and then send the worker the actual chunk of lines.
PI_Write( toWorker[nextChannel], "%d", lineNum);
PI_Write( toWorker[nextChannel], "%^s", strlen(buffer) + 1, &buffer);
// Get ready to continue collecting lines and sending chunks of lines to workers.
buffer[0] = '\0';
bufferPos = 0;
lineNum += linesSinceSending;
linesSinceSending = 0;
}
}
}
printf(">> Telling workers they are done.\n");
// Send workers signal that there is no more data to work on.
for(i = 0; i < workerCount; i++){
PI_Read(result[i], "%c", &signal);
PI_Write( toWorker[i], "%d", END_OF_DATA);
}
printf(">> Collecting data from workers.\n");
// Gather the results from each worker, and write the results to a file as they are gotten.
for(i = 0; i < workerCount; i++){
PI_Read(result[i], "%^s", &workerResultLength, &workerResult);
fprintf(outputFile, "%s", workerResult);
free(workerResult);
}
printf(">> ENDING PARALLEL... <<\n");
}