Search DaniWeb - semaphore

Re: Semaphore - what is that? 19 Years Ago by blud Semaphore's are what the system uses to run processes, kind … inodes on a disk, there are a limited number of Semaphore's available to access by files at any given time…. Usually when Semaphore's are completely used it is because a software application… semaphore help 12 Years Ago by Nakeo …Btime2, Etime1, Etime2; // time pointers Semaphore semaphore(123, 2); semaphore.Init(0,1); semaphore.Init(1,99); srand(time(NULL));// …; randomnums; index++) // random number loop { semaphore.Wait(0); semaphore.Wait(0); oldnumber = semaphore.ReadValue(1); newnumber=rand() % 100; cout … Re: semaphore help 12 Years Ago by sundip Compilation does not mean a correct program. Have you try to debug your program? Just by a quick look on your program i am unable to understand the use of [CODE] line 33. semaphore.Wait(0); Line 34. semaphore.Wait(0);[/CODE] Re: semaphore help 12 Years Ago by Nakeo … to understand the use of [CODE] line 33. semaphore.Wait(0); Line 34. semaphore.Wait(0);[/CODE][/QUOTE] Those two lines where… Semaphore - what is that? 19 Years Ago by Gandalf …/2004-July/002269.html[/url] My question is what is Semaphore? What casues it to end up within 3 days and… get when via SSH i make a command ipcs -u -------Semaphore Status -------- used arrays = 93 allocated semaphores = 93 semaphore instead synchronized methods? 10 Years Ago by nikolaos … class SemaphoreMultithreadingExample { static int counter = 0; static Semaphore semaphore = new Semaphore(1); public static void incrementCounter(){ try { semaphore.acquire(); counter++; semaphore.release(); } catch (InterruptedException ex… Re: semaphore instead synchronized methods? 10 Years Ago by nikolaos I think that a disadvantage of semaphore is that the thread using semaphore.acquire() could be interrupted. I 've read that when we are dealing with a small number of threads synchronized methods are faster but as the number of threads increases semaphores are faster. Thank you for your answer. Re: semaphore instead synchronized methods? 10 Years Ago by JamesCherrill The main advantage of Semaphore is that you can limit access to n threads, not just one thread, at a time. Personally I would use synchronised to limit to one thread at atime, mainly because its simpler and more obvious code. Semaphore explanation (signals : wait/up etc) 11 Years Ago by BryantFury … The notes I have are rather vague about comparing two semaphore operations (like in this case) I have attempted the …)E this is beginning from A with changes due to semaphore signalling. Other possible orders I have in mind are:… change)E I feel I am not correctly analysing the semaphore operations (and admittingly they do confuse me) B)some… Semaphore Understanding 12 Years Ago by Gaiety …when the process is going to sleep the semaphore is not cleared so i expect sem unavailable)… atleast once in course of execution. #include <semaphore.h> #include <stdio.h> #include…PROT_READ |PROT_WRITE,MAP_SHARED,fd,0); close(fd); /* create, initialize semaphore */ if( sem_init(&mutex,1,1) < 0)… Re: Semaphore Understanding 12 Years Ago by Banfa … execution for potentially an infinite amount of time if the semaphore value is already 0 in order to lock the… semaphore. It only returns -1 if there is an error, including … could try calling `sem_trywait` which will return immediately if the semaphore can not be locked with a value of -1 and… Re: Semaphore(Binary & Counting) 12 Years Ago by mike_2000_17 … in (and didn't check out yet), that's a semaphore. Of course, this requires that everyone is diligent enough not… particular room that is available. This is why the counting semaphore is not as useful, at least, by itself. There are… resource pool), in which case you might use a counting semaphore as part of the solution, but often not. The reason… semaphore and critical section 12 Years Ago by sydsine Plz explain m the following wid example if possible. These ques. Are basically for interview purpose 1. System clock 2. Semaphore 3. Mutex 4. Monitor 6. Difference b/w monitor and semaphore 7. Backup and restore 6. Does deadlock happens in a system when. Is system hang a deadlock plz reply .. Semaphore Problem 12 Years Ago by smith32 … properly for writer/reader problem. I think something with the semaphore. but can't solve and online can't help me… too. [CODE] semaphore mutex, read, write; void *reader(void *argv) { char buffer[200… Semaphore Problem 12 Years Ago by smith32 …'m trying to do the third writer/reader problem with semaphore (as mention on wiki). But it's not working properly…;pthread.h> #include <stdlib.h> #include <semaphore.h> #include <string.h> #include <fcntl… Semaphore(Binary & Counting) 12 Years Ago by Ankit_Parmar What is the difference between Binary Semaphore & Counting Semaphore? What will be situation to prefer one from both of them? Re: Semaphore(Binary & Counting) 12 Years Ago by rubberman It depends upon how many threads are allowed to access a resource at a time. A binary semaphore allows only one, whereas a counting semaphore may only allow N accesses at a time. The counting version is not frequently used, but it may be useful for some situations. semaphore applied to parent and child process 10 Years Ago by haresh.sankarraj Hi members, This is a program i wanted to implement semaphore between parent and child processes which are trying to access …/types.h> #include <unistd.h> #include <semaphore.h> #include <stdlib.h> #include <errno… semaphore implementation using the linked list 14 Years Ago by bappee11 hey guys i,m having a bit problem with the programming..... i have to implement semaphore with two function called wait() and signal() using the linked list and array or stack in c++ semaphore/mutex 11 Years Ago by kesuke Can I use semaphore or mutex on MikroC? If you know , please tell me the function name or exsample code. Re: Semaphore with value 0 9 Years Ago by serpi90 … uses `sem_post` The case you mentioned of the semaphore being initialized with 1, used to protect *shared memory…* segments is the case of a **mutex**, or semaphore for *mutual exclusion*. You could also achieve this initializing… possibilities. * **A** posts and **B** waits * The semaphore value is 0, **A** uses `sem_post` and it becomes … Re: Semaphore with value 0 9 Years Ago by Moschops …can't have any". If you're using a semaphore system that someone else wrote, they will probably have …already decided what a zero semaphore means and you should check the documentation. It is … interpret a zero (or other such nullesque value) valued semaphore to mean "nobody is using this data right now… Re: Semaphore with value 0 9 Years Ago by Moschops > The only restriction of a semaphore is that it's value can not be less than zero. I use the value of -1 on a semaphore to indicate that it is not being used (i.e. does not currently refer to any particualar object or data). Stuck in Readers-Writers problem using Semaphore 14 Years Ago by skyzer …ve found an example of how to use Semaphore and made my code into there for Readers… final Random rand = new Random(); private static Semaphore sm = new Semaphore(2); String text = "Beginning of the… thrdsync.startThreads(); } }[/CODE] [QUOTE]Semaphore(int permits) Creates a Semaphore with the given number of permits and … System V to POSIX Semaphore Wrapper 13 Years Ago by pikpik … trying to link the library's semaphore class to the platform's semaphore implementation. The problem is that the…BSD license. Thank you, pikpik 1. The library, semaphore example [url]http://code.google.com/p/v8/source…Semaphores [url]http://www.opengroup.org/onlinepubs/009695399/basedefs/semaphore.h.html[/url] 4. The operating system's System… Semaphores - Using command line arguments to create and remove semaphore set 13 Years Ago by mashhype …[j+3]) == atoi(argv[argc-1])) break; } /* Create semaphore */ if ((sem_id = semget(ipc_key, ns, IPC_CREAT | IPC_EXCL | 0666…: File exists"); exit(1); } printf ("Semaphore identifier %d\n", sem_id); /* Set arg (the…("semctl : GETVAL"); exit(4); } printf ("Semaphore %d has value of %d\n",i, sem_value); }… Re: mutex and semaphore 12 Years Ago by mike_2000_17 …the difference between a mutex and a *binary* semaphore is that the semaphore is a more general mechanism which makes it … scenario is that multiple threads can increase (lock) the semaphore when they need to, and decrease (unlock) it when…just like having a number of mutexes instead of one semaphore count. It's just a simpler (but sufficient … Re: Stuck in Readers-Writers problem using Semaphore 14 Years Ago by moutanna … little changes: import java.util.Random; import java.util.concurrent.Semaphore; import java.util.logging.Level; import java.util.logging.Logger…; private static final Random rand = new Random(); private static Semaphore sm = new Semaphore(2, true); String text = "Beginning of the Book… how to check if semaphore is lock efficiently 13 Years Ago by neti1987 … some code, but only after the first locked the semaphore. right now I do it with busy-waiting: [… x; // wait untill the main thread will lock the first semaphore: while (1) { x = semctl ( sem1 , 0 , GETNCNT); // …gt; 0) break; // if the main thread locked the first semaphore - break the loop. usleep(1); // else - wait milisecond … Re: how to check if semaphore is lock efficiently 13 Years Ago by neti1987 …to it ?[/QUOTE] I have to lock a semaphore in the main thread. and right after that…code. the problem is, that when I locked the semaphore - the program is stucked - and this is not… if the main thread already locked the semaphore. (of course I cannot write it right …after the semaphore lock - because it won't run)…