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Re: [pygame] Screeching, Howling Garbage in One Ear pygame.sndarray

On 5/5/06, Luke Paireepinart <rabidpoobear@xxxxxxxxx> wrote: 
but the line
    for l in range(0,length):

would be faster if you said
l = 0
while l < length:
    l+=1

I believe,
because then python doesn't have to generate an array of integers
that's (length) long, which is what the range() function does in the for
loop version.

while doing an explicit counter doesn't hog a bunch of memory like
range does, it really isn't any faster.... the builtin xrange on the
other hand, which uses a generator to return the list values is
probably the best way to do a simple counter-type for loop

on my machine, range is a memory hog, but is faster than an explicit
counter until a loop of about 1 million and range gets much worse from
there, while xrange was always less than half the speed of the
explicit counter (makes sense, when it's less than half the code)

for the curious, attached is a some python code to see the difference
between range, xrange and an explicit counter on your own machine(s)

import timeit

def iter_counter(length):
	l = 0
	while l < length:
		num = l
		l+=1
	return num

def iter_range(length):
	for l in range(0,length):
		num = l
	return num

def iter_xrange(length):
	for l in xrange(0,length):
		num = l
	return num

def print_function_timings(func_name, count):
	statement = "%s(%d)" % (func_name, count)
	print " timed:",func_name
	timer = timeit.Timer(statement, "from __main__ import %s"%func_name)
	results = timer.repeat(3, 1)
	print "  average:", reduce(lambda a,b: a+b, results)/len(results)
	print "  min:", min(results)
	return min(results)
	
def print_function_comparison(loop_size):
	print "Comparing",loop_size,"iterations"
	range_time = print_function_timings("iter_range", loop_size)
	counter_time = print_function_timings("iter_counter", loop_size)
	xrange_time = print_function_timings("iter_xrange", loop_size)
	print "counter vs. range: %.1f%% less time"%(100*(range_time - counter_time)/range_time)
	print "xrange vs. counter: %.1f%% less time"%(100*(counter_time - xrange_time)/counter_time)
	print ""

print_function_comparison(10000)
print_function_comparison(1000000)
print_function_comparison(100000000)