python - Using multiprocessing to utilize all cores of the CPU -

i trying calculate number of floating point operations per second cpu can perform, wrote following program:

import time import sys multiprocessing import process   numofloops = 10000000  if (len(sys.argv) != 2):     print "correct usage: python cpu.py 'no_of_processes'"     sys.exit()  #function each process def fpops():     = float(0.0)     in xrange(0, numofloops):         += 0.5         #print #for debugging purpose  processes = [] numofprocesses = int(sys.argv[1]) numofops = numofloops * numofprocesses  in xrange(0, numofprocesses):     processes.append(process(target=fpops))  start = time.time() process in processes:     process.start() process in processes:     process.join() end = time.time()  exectime = end - start print "exec time " , exectime   flops = (float(numofops/exectime)) print "flops : " , flops 

the program calculates time (exectime) takes perform 'n' number of floating point operations , 'n / exectime' gives me flops value want.

but, flops value decreases increase number processes. expecting reduce since processes performing more number of operations per second because run in parallel. doing wrong??