Multi-threading and file access assignment (test on Dual-Core)
Here is the story (skip it if you are not interested skip directly to the Problem). I have an assignment to do on Dual core. Take some code that counts words in a file and write it using multi-threading and semaphores. I looked at the code - it is horrible, really horrible... I thought if they want me to use semaphores - why not to give me some sample that really requires use of it? So I change the code a little bit... And a little bit more and come with this version that does the task - calculates the number of words in the file, but does not require semaphores.
Description of the program: Program can be run without parameters (it uses one thread for calculations) or with 1 param from 0 to 9 that determines number of threads to use (0 stands for 10 threads). The only locking is used - are inside function fgets, no additional locks are required in my code... Program calculates number of words in the file "InFile1.txt" (sample file is attached, filename is hardcoded, to use other file its name should be changed to that and it should be put in the folder together with exe)
Problem: I have no idea if running this program with 1 thread and 2 threads make any difference on dualcore. So if someone can run it once without params and once as <Threaded 2> on Dualcore system I will appritiate.
Thanks.
Here is the code.
Code:
/***********************************************************
* Threaded.c
************************************************************
* Description
* Counts number of words in the file InFile1.txt
* Uses from 1 to 10 threads to perform the calculations
* depending on the command line arguments
*************************************************************
* Compiled using MSVS Express 2005
* With Warning 4996 disabled
*************************************************************
* Usage:
* Threaded
* for running in the single thread mode
* Threaded x
* where x is from 1 to 9 to run using x threads
* Threaded 0
* to run using 10 threads
*************************************************************
* (c) vart 2007
*************************************************************/
#include <windows.h>
#include <stdio.h>
#include <time.h>
#define MAX_THREADCOUNT 10
struct TotalWords
{
int TotalEvenWords;
int TotalOddWords;
};
static struct TotalWords empty = {0};
struct Params
{
struct TotalWords count;
FILE* fd;
};
void GetWordAndLetterCount(unsigned char *Line, struct TotalWords* current)
{
int Letter_Count = 0;
int i;
for (i=0;Line[i];i++)
{
if (!isspace(Line[i]))
Letter_Count++;
else
{
if(Letter_Count > 0)
{
if (Letter_Count % 2)
{
current->TotalOddWords++;
}
else
{
current->TotalEvenWords++;
}
Letter_Count = 0;
}
}
}
if(Letter_Count > 0)
{
/* last word can have no white space at the end - we still need to count it */
if (Letter_Count % 2)
{
current->TotalOddWords++;
}
else
{
current->TotalEvenWords++;
}
Letter_Count = 0;
}
return ;
}
DWORD WINAPI CountWords(LPVOID arg)
{
struct Params* current = (struct Params*)arg;
unsigned char inLine[BUFSIZ];
current->count = empty; /* initializes counters to zero */
while (fgets((char*)inLine,sizeof inLine,current->fd))
{
GetWordAndLetterCount(inLine, ¤t->count) ;
}
return 0;
}
int main(int argc, char* argv[])
{
int threadCount = 1;
HANDLE hThread[MAX_THREADCOUNT];
struct Params par[MAX_THREADCOUNT];
FILE* fd = NULL;
if(argc == 2 && isdigit(argv[1][0]))
threadCount = argv[1][0] - '0';
if (threadCount == 0) threadCount = 10;
fd = fopen("InFile1.txt", "r"); // Open file for read
if(fd == NULL)
perror("Cannot open file");
else
{
clock_t start,stop;
start = clock();
if(threadCount == 1)
{
par[0].fd = fd;
CountWords(par);
}
else
{
int i;
for (i = 0; i < threadCount; i++)
{
par[i].fd = fd;
hThread[i] = CreateThread(NULL,0,CountWords,par+i,0,NULL);
}
WaitForMultipleObjects(threadCount, hThread, TRUE, INFINITE);
for (i = 1; i < threadCount; i++)
{
par[0].count.TotalEvenWords += par[i].count.TotalEvenWords;
par[0].count.TotalOddWords += par[i].count.TotalOddWords;
}
}
fclose(fd);
stop = clock();
printf("Total Words = %8d\n\n", par[0].count.TotalEvenWords + par[0].count.TotalOddWords);
printf("Total Even Words = %7d\nTotal Odd Words = %7d\n", par[0].count.TotalEvenWords, par[0].count.TotalOddWords);
printf(" Calculated during %f clocks\n", (double)(stop-start));
}
}
The uploaded sample file is really short. Using this file time results are zeroes on my notebook... So for real test I'd ask to provided some text file in the size of around 5M or bigger ( could not upload it here)...
