add a bitequal() function

[bgruening]

I added a bitequal() function to calculate the same as (a & b).count().

Thanks for this great library.
Björn

[bgruening]

Hi Ilan,

any chance to get this merged?
Thanks,
Bjoern

[bgruening]

Is there anything I can do to get this PR merged?

[andre-merzky]

Hey @bgruening,

this repo has been silent for quite a while, and we thus created a fork at https://github.com/diamondman/bitarray/.

If you are interested, please feel free to transplant your pull request to the forked repo, we would be very happy to begin the code review and merge into bitarray before pushing out a new release. If you do not have the time to do so, we would kindly ask your permission to do the PR transfer our-self. If you could ping back in the next couple of days, one way or the other, that would be great.

Many thanks!

[bgruening]

@andre-merzky thats great to hear! I'm travelling the next days, so if you can take this PR over feel free to do so. Hopefully, it's useful!

[andre-merzky]

Thanks for the note, @bgruening - we'll do that then, and will ping back. Take care :)

[diamondman]

diamondman#9

[andre-merzky]

Hmm, isn't count() exactly what you are looking for?

#!/usr/bin/env python

import bitarray
import random
import time
import sys

n  = 1024*1024*1024
ba = bitarray.bitarray(n)

t_0 = time.time()
for i in range(1000*1000):
    ba.setrange(i*1000, i*1000+999, True)
t_1 = time.time()
print ba.count()
t_2 = time.time()
print 'timer 1: %5.2f' % (t_1 - t_0)
print 'timer 2: %5.2f' % (t_2 - t_1)

gives

$ python ./test.py
1000000000
timer 1:  0.53
timer 2:  0.05

On Tue, Nov 22, 2016 at 1:51 PM, Rémi Adon notifications@github.com wrote:

Hi everyone,
I didn't want to create new issue because I think my question is related.

I would like to get the cardinality of a bitarray, i.e the number of bits
set to 1, as defined in Java's BitSet class
https://docs.oracle.com/javase/7/docs/api/java/util/BitSet.html#cardinality()

using bitequal I could try something like:

b = bitarray.bitarray(bitarray.bitarray('1') * my_bitarray.length)
cardinality = bitarray.bitequal(my_bitarray, b)

or I could simply use sum:

cardinality = sum(1 for i in my_bitarray if i)

I did not try bitequal but sum is not that fast (between 10 and 50 ms for
1 million bits on my machine), I mean not that fast if i need to
recompute/use it many times.

Is there a faster way to compute the cardinality ?

[remiadon]

ow thank you @andre-merzky , my bad