xor: how come so slow?

[Peter Otten]

Michele wrote:

> I'm trying to encode a byte data. Let's not focus on the process of
> encoding; in fact, I want to emphasize that the method
> create_random_block takes 0.5s to be executed (even Java it's faster) on
> a Dual-Core 3.0Ghz machine:
> 
> took 46.746999979s, avg: 0.46746999979s

> How should I decrease the execution time?

Use numpy. You should be able to swap in the following in your script

    import numpy
    from numpy.core import multiarray as ma
    class Encoder(object):
        def create_random_block(self, data, seed, blocksize):
            number_of_blocks = len(data)//blocksize
            random.seed(seed)
            random_block = ma.fromstring("0"*blocksize, numpy.uint8)

            for index in range(number_of_blocks):
                if random.getrandbits(1):
                    block =
ma.fromstring(data[blocksize*index:blocksize*index+blocksize], numpy.uint8)
                    random_block ^= block
            return random_block.tostring()

There are absolutely no warranties as I'm just a random tinkerer when it
comes to numpy. But if it works you should get a nice speedup...

Peter