Question
Help with fixing following C program : fix the program: 1) The function run_enzyme() needs to be created. Please see the notes inside enzyme.c. 2)
Help with fixing following C program :
fix the program:
1) The function run_enzyme() needs to be created. Please see the notes inside enzyme.c.
2) The function 'make_enzyme_threads' has a memory bug. Fix this by simply re-ordering the lines in this function. It is simple fix but may take a while for you to find it.
3) The function 'join_on_enzymes' is incomplete. Read the relevant man pages and figure out how the function is supposed to work. Then insert the correct code snippets into 'whatgoeshere'.
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#include "enzyme.h"
int please_quit;
int use_yield;
int workperformed;
// The code each enzyme executes.
void *run_enzyme(void *data) {
/* This function should :
1. cast the void* pointer to thread_info_t*
2. initialize the swapcount to zero
3. Set the cancel type to PTHREAD_CANCEL_ASYNCHRONOUS
4. If the first letter of the string is a C then call pthread_cancel on this thread.
5. Create a while loop that only exits when please_quit is nonzero
6. Within this loop: if the first character of the string has an ascii value greater than the second (s[0] >s[1]) then -
Set workperformed=1, increment swapcount for this thread, then swap the two characters around
If "use_yield" is nonzero then call pthread_yield at the end of the loop.
7. Return a pointer to the updated structure.
*/
while(0) {
sched_yield();
};
return NULL;
}
// Make threads to sort string.
// Returns the number of threads created.
// There is a memory bug in this function.
int make_enzyme_threads(pthread_t * enzymes, char *string, void *(*fp)(void *)) {
int i,rv,len;
thread_info_t *info;
len = strlen(string);
info = (thread_info_t *)malloc(sizeof(thread_info_t));
for(i=0;i info->string = string+i; rv = pthread_create(enzymes+i,NULL,fp,info); if (rv) { fprintf(stderr,"Could not create thread %d : %s ", i,strerror(rv)); exit(1); } } return len-1; } // Join all threads at the end. // Returns the total number of swaps. int join_on_enzymes(pthread_t *threads, int n) { int i; int totalswapcount = 0; int whatgoeshere=0; // just to make the code compile // you will need to edit the code below for(i=0;i void *status; int rv = pthread_join(threads[i],&status); if(whatgoeshere) { fprintf(stderr,"Can't join thread %d:%s. ",i,strerror(rv)); continue; } if ((void*)whatgoeshere == PTHREAD_CANCELED) { continue; } else if (status == NULL) { printf("Thread %d did not return anything ",i); } else { printf("Thread %d exited normally: ",i);// Don't change this line int threadswapcount = whatgoeshere; // Hint - you will need to cast something. printf("%d swaps. ",threadswapcount); // Don't change this line totalswapcount += threadswapcount;// Don't change this line } } return totalswapcount; } /* Wait until the string is in order. Note, we need the workperformed flag just in case a thread is in the middle of swapping characters so that the string temporarily is in order because the swap is not complete. */ void wait_till_done(char *string, int n) { int i; while(1) { sched_yield(); workperformed=0; for(i=0;i if (string[i] > string[i+1]) { workperformed=1; } if(workperformed==0) break; } } void * sleeper_func(void *p) { sleep( (int) p); // Actually this may return before p seconds because of signals. // See man sleep for more information printf("sleeper func woke up - exiting the program "); exit(1); } int smp2_main(int argc, char **argv) { pthread_t enzymes[MAX]; int n,totalswap; char string[MAX]; if (argc <= 1) { fprintf(stderr,"Usage: %s exit(1); } strncpy(string,argv[1],MAX); // Why is this necessary? Why cant we give argv[1] directly to the thread functions? please_quit = 0; use_yield =1; printf("Creating threads... "); n = make_enzyme_threads(enzymes,string,run_enzyme); printf("Done creating %d threads. ",n); pthread_t sleeperid; pthread_create(&sleeperid,NULL,sleeper_func,(void*)5); wait_till_done(string,n); please_quit = 1; printf("Joining threads... "); totalswap = join_on_enzymes(enzymes, n); printf("Total: %d swaps ",totalswap); printf("Sorted string: %s ",string); exit(0); }
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