Pyhon 2.x or 3.x, which is faster?

[BartC]

On 08/03/2016 02:45, Mark Lawrence wrote:
> On 08/03/2016 01:47, BartC wrote:

>> The Python timing for that file is around 20 seconds, time enough to
>> read 10000 copies from the disk.
>>
>> And a C program reads /and decodes/ the same file from the same disk in
>> between 0.1 and 0.2 seconds.
>>
>
> So how much of that time is Python startup time, compared to C which is
> effectively zero?

Virtually zero as well.

That's if by start-up time you mean how long between invoking Python 
with the name of the main module, executing all the imports and defs in 
the main and imported modules, until it starts properly executing code.

In the jpeg test, perhaps 50ms. And it would not depend on the size of 
the input since the start-up routines won't know that.

> Or are you suggesting that C code is always 100 times
> faster than Python?

This test is one of those where C can clearly do a good job of reducing 
most of it down to a series of tight loops where everything is in registers.

But yes, numeric algorithms are generally going to be a magnitude or two 
faster in optimised C, compared with CPython executing pure Python code.

(But I also remember posting a test in comp.lang.c that was faster in 
Python than in C. It involved strings and Python had the edge because it 
used counted strings. A straightforward C version would use 
zero-terminated strings, although it could be speeded up with a bit more 
work.)

 > Of course I'd like to see you write C code 100
> times faster than Python,

No, it would take longer. But the final result could be run hundreds of 
times a day by millions of people.

-- 
Bartc