Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Present your own fully documented and tested programming example illustrating the problem of unbalanced loads. Describe the use of OpenMP's scheduler as a means of mitigating this problem.
The below example shows a number of tasks that all update a global counter. Since threads share the same memory space, they indeed see and update the same memory location. The code returns a false result because updating the variable is much quicker than creating the thread as on a multicore processor the chance of errors will greatly increase. If we artificially increase the time for the update, we will no longer get the right result. All threads read out the value of sum, wait a while (presumably calculating something) and then update.
#include
#include "pthread.h"
int sum=0;
void adder() {
int sum = 0;
int t = sum; sleep(1); sum = t+1;
return;
}
#define NTHREADS 50
int main() {
int i;
pthread_t threads[NTHREADS];
printf("forking\n");
for (i=0; i if (pthread_create(threads+i,NULL,&adder,NULL)!=0) return i+1; printf("joining\n"); for (i=0; i { if (pthread_join(threads[i],NULL)!=0) return NTHREADS+i+1; printf("Sum computed: %d\n",sum); } return 0; } The use of OpenMP is the parallel loop. Here, all iterations can be executed independently and in any order. The pragma CPP directive then conveys this fact to the compiler. A sequential code can be easily parallelized this way. #include #include #include "pthread.h" int sum=0; void adder() { int sum = 0; int t = sum; sleep(1); sum = t+1; return; } #define NTHREADS 50 int main() { int i; pthread_t threads[NTHREADS]; printf("forking\n"); #pragma omp for for (i=0; i if (pthread_create(threads+i,NULL,&adder,NULL)!=0) return i+1; } printf("joining\n"); for (i=0; i { if (pthread_join(threads[i],NULL)!=0) return NTHREADS+i+1; printf("Sum computed: %d\n",sum); } return 0; }
if (pthread_create(threads+i,NULL,&adder,NULL)!=0) return i+1;
printf("joining\n");
for (i=0; i { if (pthread_join(threads[i],NULL)!=0) return NTHREADS+i+1; printf("Sum computed: %d\n",sum); } return 0; } The use of OpenMP is the parallel loop. Here, all iterations can be executed independently and in any order. The pragma CPP directive then conveys this fact to the compiler. A sequential code can be easily parallelized this way. #include #include #include "pthread.h" int sum=0; void adder() { int sum = 0; int t = sum; sleep(1); sum = t+1; return; } #define NTHREADS 50 int main() { int i; pthread_t threads[NTHREADS]; printf("forking\n"); #pragma omp for for (i=0; i if (pthread_create(threads+i,NULL,&adder,NULL)!=0) return i+1; } printf("joining\n"); for (i=0; i { if (pthread_join(threads[i],NULL)!=0) return NTHREADS+i+1; printf("Sum computed: %d\n",sum); } return 0; }
{
if (pthread_join(threads[i],NULL)!=0) return NTHREADS+i+1;
printf("Sum computed: %d\n",sum);
return 0;
The use of OpenMP is the parallel loop. Here, all iterations can be executed independently and in any order. The pragma CPP directive then conveys this fact to the compiler. A sequential code can be easily parallelized this way.
#pragma omp for
for (i=0; i if (pthread_create(threads+i,NULL,&adder,NULL)!=0) return i+1; } printf("joining\n"); for (i=0; i { if (pthread_join(threads[i],NULL)!=0) return NTHREADS+i+1; printf("Sum computed: %d\n",sum); } return 0; }
for (i=0; i { if (pthread_join(threads[i],NULL)!=0) return NTHREADS+i+1; printf("Sum computed: %d\n",sum); } return 0; }
Define seek time and latency time. The time taken by the head to move to the appropriate cylinder or track is known as seek time. Once the head is at right track, it must wait
Define the “turn-around” time of a user job Turn- around time is total time taken to execute the job.
Describe the differences between symmetric and asymmetric multiprocessing. What are three advantages and one disadvantage of multiprocessor systems? Symmetric multiprocessing t
LRU evicts the page which was last accessed the farthest into the past of any page resident in physical memory, i.e. the least-recently used page. LRU approximates OPT when the rec
Consider a particular system that does not have an interrupting clock. The only way a thread can lose the processor is to voluntarily surrender it. Additionally, the operating sy
Define memory management In multiprogramming system the user part of memory should be further subdivided to accommodate multiple processes. The task of subdivision is carried o
What is input output operation ?
Q. The accelerating search for described in subsequent exercise is typical of hard-disk drives. By contrast floppy disks and several hard disks manufactured before the mid-1980s t
What are the different thread levels? There are two broad type of thread implementation: User-Level Threads -- Thread Libraries. Kernel-level Threads -- System Calls.
Question: a) What special measures must be taken to ensure the reliability, availability, and security of electronic commerce and digital business process? b) What are the c
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd