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Perfomance Issue

See original GitHub issue

I have tested the simple code with Brython and Javascript:

<!doctype html>
<html>
    <head>
        <meta charset="utf-8">
        <script src="brython.js"></script>
        <script src="brython_modules.js"></script>
    </head>

    <body onload="brython(1)">
        <script type="text/python">
            from browser import console

            console.time('python')
            list = []
            i = 0
            while i < 100000:
                list.append(i)
                i += 1
            console.timeEnd('python')
        </script>
        <script>
            console.time('javascript')
            var list = [];
            for (var i = 0; i <= 100000; i++) {
                list.push(i);
            }
            console.timeEnd('javascript')
        </script>
        <div id="root"></div>
    </body>
</html>

And the results in Chrome are the following:

javascript: 2.59716796875ms
brython.js:5316 using indexedDB for stdlib modules cache
brython.js:9073 python: 289.85302734375ms

Profiling from Chrome is attached:

Profile-20200617T123405.zip

Also according the report Brython seems to be only 3 times slower … strange …

Seems like it should be investigated as time will be …

Issue Analytics

State:
Created 3 years ago
Comments:33 (33 by maintainers)

Top GitHub Comments

2reactions

PierreQuentelcommented, Jun 18, 2020

I have not accepted PR #1422 for reasons explained in detail in the comment, but using a cache to speed up attribute lookup is certainly a good idea !

The flexibility of arguments parsing in Brython (positional, keywords, defaults, positional-only, keyword-only, etc…) makes it hard to implement it efficiently in Javascript. By default, $B.args() is used, as it covers all the possible combinations.

In commit 0b154e018b7972f9f6d747d03dcc5b8f02994769 I have replaced it by a call to 2 functions for list.append()

    $B.check_no_kw("append", self, x)
    $B.check_nb_args("append", 2, arguments)

It makes the code above not far from 2 times faster than with $B.args(). The same optimization can be done for all methods that don’t support keyword arguments and expect exactly a given number of arguments, without default values.

1reaction

redradistcommented, Jun 19, 2020

@PierreQuentel

@redradist All I can say is, good luck ! Checking that a variable didn’t change just by looking at the code (static analysis) is terribly difficult because of the flexibility of the language. For instance:
* module **`mymodule.py`**
bla = globals
* module **`main.py`**
from mymodule import *

class A:

    @property
    def x(self):
        bla()["i"] = "z"

a = A()
i = 5
a.x
print(i + 1) # must fail, i is now "z"...
How would static analysis of main.py guess that the expression a.x changed the value of i ?

Initial Proof of Concept will be done at https://github.com/redradist/DOpter

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