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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