Python: Difference between revisions
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* [[multiprocess.Lock replacement using SYSV]] |
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<nowiki> |
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* [[Converting Gregorian dates to day numbers]] |
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import ctypes |
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* [[numpy surprises]]] |
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import os |
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import sys |
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IPC_CREAT=00001000 |
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# man shm_overview |
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# for f in `find /lib/lib* -type f `; do nm -D $f|grep sem_open && echo found in library: $f; done |
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locksUsed=0 |
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class Lock: |
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def __init__(self): |
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#http://www.dailyfreecode.com/code/create-shared-memory-print-id-shared-2183.aspx |
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global locksUsed |
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self.fname="/tmp/Py-Lock%4i"%locksUsed |
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self.libc = ctypes.cdll.LoadLibrary("/lib/libc.so.6") |
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self.librt = ctypes.cdll.LoadLibrary("/lib/librt.so.1") |
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f=open(self.fname,"w") |
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f.write("0") |
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f.close() |
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self.key=self.libc.ftok(fname, 0x55) |
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print "ftok returned:", self.key |
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r=self.libc.semget(self.key, 1, IPC_CREAT|0666) |
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print "semget returned: ",r |
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si=self.librt.sem_init(self.mem, 1, 1) |
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print "sem_init returned:", si |
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locksUsed+=1 |
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def acquire(self): |
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self.librt.sem_wait(self.sm) |
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def release(self): |
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self.librt.sem_post(self.sm) |
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#class Lock_POSIX: |
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# def __init__(self): |
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# global locksUsed |
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# self.librt = ctypes.cdll.LoadLibrary("/lib/libpthread.so.0") |
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# |
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# try: |
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# self.librt.sem_unlink("/PyLock%4i"%locksUsed) |
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# except: |
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# pass |
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# self.sm=self.librt.sem_open("/PyLock%4i"%locksUsed, os.O_RDWR|os.O_CREAT, 0x1ff, 1) |
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# if sm==0: |
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# print "sem_open returned:", self.sm |
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# sys.exit() |
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# #si=self.librt.sem_init(self.sm, 1, 1) |
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# print "sem_init returned:", si |
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# if self.sm>=0: |
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# locksUsed+=1 |
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# |
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# def acquire(self): |
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# self.librt.sem_wait(self.sm) |
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# |
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# def release(self): |
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# self.librt.sem_post(self.sm) |
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if __name__== "__main__": |
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import time |
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import random |
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from multiprocessing import Process |
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l=Lock() |
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def fight(i): |
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for j in range(10): |
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l.acquire() |
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for k in range(10): |
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print i |
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time.sleep(random.random()/30.) |
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print |
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l.release() |
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Process(target=fight, args=(1,)).start() |
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Process(target=fight, args=(2,)).start() |
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Process(target=fight, args=(3,)).start() |
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Process(target=fight, args=(4,)).start() |
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</nowiki> |
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<nowiki> |
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#include <sys/types.h> |
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#include <sys/ipc.h> |
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#include <sys/sem.h> |
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#include <stdlib.h> |
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#include <stdio.h> |
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int acquire(int semid){ |
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struct sembuf sops[2]; |
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sops[0].sem_num = 0; |
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sops[0].sem_op = -1; |
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sops[0].sem_flg = SEM_UNDO; |
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if (semop(semid, sops, 1) == -1) { |
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perror("acquire"); |
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exit(1); |
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} |
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} |
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int release(int semid){ |
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struct sembuf sops[2]; |
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sops[0].sem_num = 0; /* Operate on semaphore 0 */ |
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sops[0].sem_op = 1; /* Wait for value to equal 0 */ |
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sops[0].sem_flg = SEM_UNDO; |
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if (semop(semid, sops, 1) == -1) { |
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perror("release"); |
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exit(1); |
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} |
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} |
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void p(int semid, int i){ |
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int j; |
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acquire(semid); |
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for(j=0; j<10; j++){ |
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printf("%i\n",i); |
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sleep(1); |
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} |
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release(semid); |
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} |
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int main(int argc, char **argv){ |
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key_t key; |
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int semid; |
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int wait_status; |
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key=ftok("l-.l", 0x55); |
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printf("key=%i\n",key); |
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semid=semget(key, 1, IPC_CREAT|0666); |
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printf("semid=%i\n",semid); |
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release(semid); |
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printf("after first release"); |
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printf("semid=%i\n", semid); |
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if(fork()){ |
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p(semid, 1); |
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wait(&wait_status); |
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} else { |
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p(semid, 2); |
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} |
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} |
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</nowiki> |
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