[pypy-dev] pypy1.6 slow on string-heavy ops

[Aaron DeVore]

Python 2.4 introduced a change that helps improve performance of
string concatenation, according to its release notes. I don't know
anything beyond that.

-Aaron DeVore

On Thu, Aug 18, 2011 at 3:31 PM, Justin Peel <peelpy at gmail.com> wrote:
> Yes, Vincent's way is the better way to go. To elaborate more on the
> problem, string appending is O(N^2) while appending to a list and then
> joining is an O(N) operation. Why CPython is faster than Pypy at doing
> the less efficient way is something that I'm not fully sure about, but
> I believe that it might have to do with the differing memory
> management strategies.
>
> On Thu, Aug 18, 2011 at 4:24 PM, Vincent Legoll
> <vincent.legoll at gmail.com> wrote:
>> Hello,
>>
>> Try this:
>>
>> import sys
>>
>> fasta_file = sys.argv[1]  # should be *.fa
>> print 'loading dna from', fasta_file
>> chroms = {}
>> dna = []
>> for l in open(fasta_file):
>>    if l.startswith('>'):  # new chromosome
>>        if len(dna) > 0:
>>            chroms[chrom] = ''.join(dna)
>>        chrom = l.strip().replace('>', '')
>>        dna = []
>>    else:
>>        dna.append(l.rstrip())
>> if len(dna) > 0:
>>    chroms[chrom] = ''.join(dna)
>>
>> --
>> Vincent Legoll
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>>
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