[pypy-dev] Sorting structs

[Tuom Larsen]

Hello Carl,

thanks a lot for the clarification and for creating the ticket!


On Mon, Oct 3, 2016 at 7:28 PM, Carl Friedrich Bolz <cfbolz at gmx.de> wrote:
> Hi Tuom,
>
> The problem is the key=... argument to sort, which isn't optimized
> well. This kind of code is much faster:
>
>     wrapped_data = [(p.x, p) for p in data]
>     wrapped_data.sort()
>     data = [it[1] for it in wrapped_data]
>
> We should fix this problem. I've created an issue so it doesn't get
> lost:
>
> https://bitbucket.org/pypy/pypy/issues/2410/listsort-key-is-slow
>
> Thanks for the report!
>
> Cheers,
>
> Carl Friedrich
>
>
> On 26/09/16 22:57, Tuom Larsen wrote:
>> Dear list!
>>
>> I stumbled upon a problem and I was wondering if someone would by so
>> kind and explain to me what is going on.
>>
>> The problem is sorting 2 000 000 points by `x` coordinate:
>>
>>     from random import random
>>     from time import time
>>
>>     class point(object):
>>         def __init__(self, x, y):
>>             self.x, self.y = x, y
>>
>>     data = [point(random(), random()) for i in range(2000000)]
>>
>>     t = time()
>>     data.sort(key=lambda p:p.x)
>>     print time() - t
>>
>> on my machine in runs 8.74s under PyPy 5.4.1 on MacOS. I then try to
>> sort the points in JavaScript:
>>
>>     var data = [];
>>     for (var i=0; i<2000000; i++) {
>>         data.push({x:Math.random(), y:Math.random()});
>>     }
>>
>>     console.time('sorting');
>>     data.sort(function(a, b) { return a.x - b.x; });
>>     console.timeEnd('sorting');
>>
>> and it runs in 3.09s under V8 5.3.
>>
>> I was just wondering, why is it nearly 3x slower under PyPy than it is
>> under V8? Is there any way I could make the code run faster?
>>
>> Thank you in advance!
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>
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