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Illuminatus's scratchpad

by Illuminatus (Curate)
on Mar 31, 2011 at 14:42 UTC ( #896639=scratchpad: print w/ replies, xml ) Need Help??

freerun.c
#include <pthread.h> #include <stdio.h> #include <time.h> typedef struct { int i; int loops; } shared; void *worker( void *arg ) { shared *s = (shared*)arg; int i = 0; for( i=0; i < s->loops; ++i ) { ++s->i; } return; } int main( int argc, char **argv ) { int i = 0, nThreads = 4; clock_t start, finish; double elapsed; pthread_t threads[32]; shared s = { 0, 1000000 }; if( argc > 1 ) nThreads = atoi( argv[1] ); if( argc > 2 ) s.loops = atoi( argv[2] ); printf( "threads:%d loops:%d\n", nThreads, s.loops ); start = clock(); for( i=0; i < nThreads; ++i ) pthread_create( &threads[ i ], NULL, &worker, &s ); for( i=0; i < nThreads; ++i ) pthread_join( threads[ i ], NULL ); finish = clock(); elapsed = (double)(finish - start) / CLOCKS_PER_SEC; printf( "count: %u time:%.6f\n", s.i, elapsed ); }
results on my Mac:

threads:4 loops:1000000
count: 2172720 time:0.079071

results on Ubuntu 9.04

threads:4 loops:1000000
count: 3215463 time:0.070000

mutex.c
#include <pthread.h> #include <stdio.h> #include <time.h> typedef struct { int i; int loops; pthread_mutex_t mutex; } shared; void *worker( void *arg ) { shared *s = (shared*)arg; int i = 0; for( i=0; i < s->loops; ++i ) { pthread_mutex_lock( &s->mutex ); ++s->i; pthread_mutex_unlock( &s->mutex ); } return; } int main( int argc, char **argv ) { int i = 0, nThreads = 4; clock_t start, finish; double elapsed; pthread_t threads[32]; shared s = { 0, 1000000 };; pthread_mutex_init( &s.mutex, NULL ); if( argc > 1 ) nThreads = atoi( argv[1] ); if( argc > 2 ) s.loops = atoi( argv[2] ); printf( "threads:%d loops:%d\n", nThreads, s.loops ); start = clock(); for( i=0; i < nThreads; ++i ) pthread_create( &threads[ i ], NULL, &worker, &s ); for( i=0; i < nThreads; ++i ) pthread_join( threads[ i ], NULL ); finish = clock(); elapsed = (double)(finish - start) / CLOCKS_PER_SEC; printf( "count: %u time:%.6f\n", s.i, elapsed ); }
Ran like dogsh*t on my Mac
But on Ubuntu 9.04

threads:4 loops:1000000
count: 4000000 time:1.050000

The Ubuntu 9.04 machine I was testing on was a Dell. FYI, if you are on a Linux machine, and want to get all the CPU info, just 'cat /proc/cpuinfo':

processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 15
model name : Intel(R) Core(TM)2 Duo CPU E4600 @ 2.40GHz
stepping : 13
cpu MHz : 1200.000
cache size : 2048 KB
(above info is per core)

Other Info:

kernel: linux 2.6.18-11 (64-bit)
gcc: 4.5.1
libc: 2.9
gcc -o mutex mutex.c -lpthread

freelock.c
#include <pthread.h> #include <stdio.h> #include <time.h> typedef struct { int i; int loops; } shared; //shared s = { 0, 1000000 }; void *worker( void *arg ) { shared *s = (shared*)arg; int i = 0; for( i=0; i < s->loops; ++i ) { //__sync_fetch_and_add( &s->i, s->i + 1 ); __sync_fetch_and_add( &s->i, 1 ); } return; } void main( int argc, char **argv ) { int i = 0, nThreads = 4; clock_t start, finish; double elapsed; pthread_t threads[32]; shared s = { 0, 1000000 };; if( argc > 1 ) nThreads = atoi( argv[1] ); if( argc > 2 ) s.loops = atoi( argv[2] ); printf( "threads:%d loops:%d\n", nThreads, s.loops ); start = clock(); for( i=0; i < nThreads; ++i ) pthread_create( &threads[ i ], NULL, &worker, &s ); for( i=0; i < nThreads; ++i ) pthread_join( threads[ i ], NULL ); finish = clock(); elapsed = (double)(finish - start) / CLOCKS_PER_SEC; printf( "count: %u time:%.6f\n", s.i, elapsed ); }
results on same Dell:

threads:4 loops:1000000
count: 4000000 time:0.240000

Just a note that, obviously, this would be intel-specific, and could perhaps vary significantly based on x86 type.
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