Stefan Behnel stefan...@behnel.de wrote in message
news:mailman.563.1283921317.29448.python-l...@python.org...
BartC, 08.09.2010 03:45:
Getting back to the OP's code again (trivial and pointless as it might
seem), I got these results:
C (gcc 3.4.5 -O3) 0.8 secs
C (DMC-o) 2.3 secs
C (lccwin32
BartC wrote:
So 'range' is just a class like any other. And that a class is something
you can blithely copy from one variable to another. And whenever you see
'range' anywhere, you can't always be certain that someone hasn't done:
range = 42
at some point.
True. I read an explanation
On Tue, 07 Sep 2010 11:00:03 +0100, BartC wrote:
for i in xrange(1):
a = a + f(i)
then unrolling the loop is even less useful. The overhead of the loop
itself is likely to be trivial compared to the cost of calling f() 100
million times -- the added complexity to shave 3 seconds
Steven D'Aprano st...@remove-this-cybersource.com.au writes:
With Python 3 and def f(x): return x+1, unrolling this loop 4x improved
speed by 15%; 4.00 minutes reduces to 3.30 minutes.
I'm afraid that I can't replicate those figures. In my test, unrolling
the loop causes a massive SLOWDOWN
Steven D'Aprano st...@remove-this-cybersource.com.au wrote in message
news:4c878be5$0$3$c3e8...@news.astraweb.com...
On Tue, 07 Sep 2010 11:00:03 +0100, BartC wrote:
for i in xrange(1):
a = a + f(i)
With Python 3 and def f(x): return x+1, unrolling this loop 4x improved
speed
Steven D'Aprano steve-remove-t...@cybersource.com.au wrote in message
news:4c85adfe$0$5$c3e8...@news.astraweb.com...
On Mon, 06 Sep 2010 11:38:22 +0100, BartC wrote:
Manually unrolling such a loop four times (ie. 4 copies of the body, and
counting only to 25 million) increased the speed
In article ny3ho.32445$la2.18...@newsfe23.ams2,
BartC ba...@freeuk.com wrote:
(BTW why doesn't Python 3 just accept 'xrange' as a
synonym for 'range'?)
If you've ever tried to maintain a legacy code base, you'll understand
why there's only one way to do it is A Good Thing.
Imagine that
In article o4oho.85508$za5.26...@newsfe16.ams2,
BartC ba...@freeuk.com wrote:
Steven D'Aprano steve-remove-t...@cybersource.com.au wrote in message
news:4c85adfe$0$5$c3e8...@news.astraweb.com...
xrange = range
There, that wasn't hard, was it?
I think I just learned more about Python than
In article roy-0ec6f2.08091107092...@news.panix.com,
Roy Smith r...@panix.com wrote:
Imagine that you're looking at some code which was written years ago, by
people who are no longer around to answer questions. In one place, you
see:
for i in range(n):
blah
and in another, you see:
for
On Sun, Sep 5, 2010 at 8:28 PM, BartC ba...@freeuk.com wrote:
One order of magnitude (say 10-20x slower) wouldn't be so bad. That's what
you might expect for a dynamically typed, interpreted language.
10/20x slower than C is only reached by extremely well optimized
dynamic languages. It would
On 9/7/2010 6:00 AM, BartC wrote:
Why should it? But if you want it, you can do it:
xrange = range
There, that wasn't hard, was it?
I think I just learned more about Python than from months of reading this
group.
So 'range' is just a class like any other. And that a class is something
you
David Cournapeau courn...@gmail.com wrote in message
news:mailman.546.1283897932.29448.python-l...@python.org...
On Sun, Sep 5, 2010 at 8:28 PM, BartC ba...@freeuk.com wrote:
One order of magnitude (say 10-20x slower) wouldn't be so bad. That's
what
you might expect for a dynamically typed,
On 08/09/2010 02:45, BartC wrote:
David Cournapeau courn...@gmail.com wrote in message
news:mailman.546.1283897932.29448.python-l...@python.org...
On Sun, Sep 5, 2010 at 8:28 PM, BartC ba...@freeuk.com wrote:
One order of magnitude (say 10-20x slower) wouldn't be so bad. That's
what
you
BartC, 08.09.2010 03:45:
Getting back to the OP's code again (trivial and pointless as it might
seem), I got these results:
C (gcc 3.4.5 -O3) 0.8 secs
C (DMC-o) 2.3 secs
C (lccwin32 -O) 2.9 secs
[...]
I've seen LuaJIT in action. It's timing for this test is 1.5 secs:
forget being only 10x
Stefan Behnel stefan...@behnel.de wrote in message
news:mailman.470.1283712666.29448.python-l...@python.org...
BartC, 05.09.2010 19:09:
All those compilers that offer loop unrolling are therefore wasting
their time...
Sometimes they do, yes.
Modifying the OP's code a little:
a = 0
for i
BartC, 06.09.2010 12:38:
why doesn't Python 3 just accept 'xrange' as a synonym for 'range'?
Because Python 3 deliberately breaks backwards compatibility in order to
clean up the language.
These are just some simple tests on my particular machine and
implementations, but they bring up
On Mon, Sep 6, 2010 at 4:08 PM, BartC ba...@freeuk.com wrote:
Stefan Behnel stefan...@behnel.de wrote in message
news:mailman.470.1283712666.29448.python-l...@python.org...
BartC, 05.09.2010 19:09:
All those compilers that offer loop unrolling are therefore wasting
their time...
Sometimes
On Mon, 06 Sep 2010 13:20:01 +0200
Stefan Behnel stefan...@behnel.de wrote:
(2) Integer arithmetic seems to go straight from 32-bits to long
integers; why not use 64-bits before needing long integers?
You are making assumptions based on Python 2, I guess. Try Python 3.1 or
later
Stefan Behnel stefan...@behnel.de wrote in message
news:mailman.485.1283772019.29448.python-l...@python.org...
BartC, 06.09.2010 12:38:
(2) Integer arithmetic seems to go straight from 32-bits to long
integers; why not use 64-bits before needing long integers?
You are making assumptions
On 9/6/2010 7:20 AM, Stefan Behnel wrote:
BartC, 06.09.2010 12:38:
(3) Since the loop variable is never used, why not have a special loop
statement that repeats code so many times?
There sort-of is, just slightly more general.
Because special cases are not special enough to break the
On Mon, 06 Sep 2010 11:38:22 +0100, BartC wrote:
Modifying the OP's code a little:
a = 0
for i in xrange(1): # 100 million
a = a + 10 # add 10 or 100
print a
Manually unrolling such a loop four times (ie. 4 copies of the body, and
counting only to 25
David Cournapeau courn...@gmail.com wrote in message
news:mailman.455.1283665528.29448.python-l...@python.org...
On Thu, Sep 2, 2010 at 7:02 PM, Michael Kreim mich...@perfect-kreim.de
wrote:
imax = 10
a = 0
for i in xrange(imax):
a = a + 10
print a
Unfortunately my Python Code
On Fri, 03 Sep 2010 21:17:44 +0100, BartC wrote:
I'm not sure the Python developers were interested in getting fast
loops.
For-loops which iterate between two numbers are amongst the easiest
things to make fast in a language. Yet originally you had to use:
for i in range(N):
I don't
On Sun, 05 Sep 2010 12:28:47 +0100, BartC wrote:
Getting the above kind of code fast requires the interpreter to be
clever enough so that it will use native machine operations on a int
type instead of converting back and forth between internal
representations.
Writing for i in
Steven D'Aprano, 05.09.2010 17:00:
Of course, a real optimizing compiler would realise that the Pascal code
did nothing at all, and compile it all away to an empty a.out file...
Which is just one of the reasons why this kind if benchmark provides no
insight into anything that should have an
Steven D'Aprano st...@remove-this-cybersource.com.au wrote in message
news:4c83b425$0$28657$c3e8...@news.astraweb.com...
On Sun, 05 Sep 2010 12:28:47 +0100, BartC wrote:
It would
be nice if you could directly code low-level algorithms in it without
relying on accelerators, and not have to
BartC, 05.09.2010 19:09:
I've thought about it (writing an independent interpreter). But I don't
know enough of the language, and a lot of it I don't understand (eg.
OOP). Besides, I think the language itself deliberately makes it
difficult to get it up to speed. Some of the reasons might be the
Maybe for the simple sum you can just use the sum builtin:
python -m timeit -s 'sum((10,)*1)'
1000 loops, best of 3: 0.0985 usec per loop
About the loop in general it's a good practice to use list comprehension and
generator expressions
2010/9/2 Michael Kreim mich...@perfect-kreim.de
On Thu, Sep 2, 2010 at 7:02 PM, Michael Kreim mich...@perfect-kreim.de wrote:
Hi,
I was comparing the speed of a simple loop program between Matlab and
Python.
My Codes:
$ cat addition.py
imax = 10
a = 0
for i in xrange(imax):
a = a + 10
print a
$ cat addition.m
imax =
Tim Wintle wrote:
[..] under the hood, cpython does something like this (in psudo-code)
itterator = xrange(imax)
while 1:
next_attribute = itterator.next
try:
i = next_attribute()
except:
break
a = a + 10
There is one thing that strikes me here: The code claims that
Ulrich Eckhardt, 03.09.2010 08:52:
Tim Wintle wrote:
[..] under the hood, cpython does something like this (in psudo-code)
itterator = xrange(imax)
while 1:
next_attribute = itterator.next
try:
i = next_attribute()
except:
break
a = a + 10
There is one thing that
Hi,
thanks a lot for your answers. I learn a lot and I like to sum up your
suggestions and show you the results of the time command on my machine:
Original code by me:
imax = 10
a = 0
for i in xrange(imax):
a = a + 10
print a
= runs (wall clock time): 1:55.14
Peter Otten
Michael Kreim, 03.09.2010 11:21:
So finally I followed the recommendation of Tim Wintle to use cython. I
did not know this before, but I figured out the following:
additionWintle2.pyx:
def addition():
cdef long imax = 10
cdef long a = 0
cdef long i
for i in
Michael,
Thanks for summarizing and sharing your results. Very interesting.
Regards,
Malcolm
--
http://mail.python.org/mailman/listinfo/python-list
Ulrich Eckhardt eckha...@satorlaser.com writes:
Tim Wintle wrote:
[..] under the hood, cpython does something like this (in psudo-code)
itterator = xrange(imax)
while 1:
next_attribute = itterator.next
try:
i = next_attribute()
except:
break
a = a + 10
There is one
On Fri, 2010-09-03 at 08:52 +0200, Ulrich Eckhardt wrote:
Tim Wintle wrote:
[..] under the hood, cpython does something like this (in psudo-code)
itterator = xrange(imax)
while 1:
next_attribute = itterator.next
try:
i = next_attribute()
except:
break
a = a +
On Fri, 03 Sep 2010 11:21:36 +0200, Michael Kreim wrote:
An anonymous Nobody suggested to use Numpy. I did not do this, because I
am very very new to Numpy and I did not figure out a Numpy specific way
to do this. Maybe a Numpy expert has something for me?
The problem with giving examples
Michael Kreim mich...@perfect-kreim.de wrote in message
news:mailman.362.1283422325.29448.python-l...@python.org...
I was comparing the speed of a simple loop program between Matlab and
Python.
My Codes:
$ cat addition.py
imax = 10
a = 0
for i in xrange(imax):
a = a + 10
print a
BartC, 03.09.2010 22:17:
for i in range(N):
which (if I understood correctly) actually created a list of N objects,
populated it with the values 0, 1, 2...N-1 (presumably using a more
sensible loop), then iterated between the values of the list!
I guess what applies here is special cases
Hi,
I was comparing the speed of a simple loop program between Matlab and
Python.
My Codes:
$ cat addition.py
imax = 10
a = 0
for i in xrange(imax):
a = a + 10
print a
$ cat addition.m
imax = 1e9;
a = 0;
for i=0:imax-1
a = a + 10;
end
disp(a);
exit;
The results look like
Michael Kreim wrote:
I was comparing the speed of a simple loop program between Matlab and
Python.
My Codes:
$ cat addition.py
imax = 10
a = 0
for i in xrange(imax):
a = a + 10
print a
Are there any ways to speed up the for/xrange loop?
Move it into a function; this
Peter Otten wrote:
Move it into a function; this turns a and i into local variables.
def f():
imax = 10
a = 0
for i in xrange(imax):
a = a + 10
print a
f()
Wow. It is still slower than Matlab, but your suggestion speeds up the
code by ca 50%.
But I do not
Michael Kreim wrote:
Peter Otten wrote:
Move it into a function; this turns a and i into local variables.
def f():
imax = 10
a = 0
for i in xrange(imax):
a = a + 10
print a
f()
Wow. It is still slower than Matlab, but your suggestion speeds up the
On Thu, 2010-09-02 at 12:02 +0200, Michael Kreim wrote:
Hi,
I was comparing the speed of a simple loop program between Matlab and
Python.
Unfortunately my Python Code was much slower and I do not understand why.
The main reason is that, under the hood, cpython does something like
this (in
Tim Wintle, 02.09.2010 14:55:
If you really need to optimise it then you can convert that module to
cython by adding a cdef, and then compile it:
cdef int i
for i in xrange(imax):
a = a + 10
print a
or you can write it in C it'll run a lot faster.
Just to get the context right here: a
Michael Kreim mich...@perfect-kreim.de writes:
Are there any ways to speed up the for/xrange loop?
Or do I have to live with the fact that Matlab beats Python in this
example?
To a point, yes. However, there are things you can do to make your
Python code go faster. One has been pointed out
Hi,
Are there any ways to speed up the for/xrange loop?
You can use psyco.
The following example should be about 4-times as fast as your example:
import psyco
psyco.full()
def f():
imax = 10
a = 0
for i in xrange(imax):
a += 10
print a
f()
regards,
On Thu, 02 Sep 2010 12:02:40 +0200, Michael Kreim wrote:
I was comparing the speed of a simple loop program between Matlab and
Python.
imax = 10
a = 0
for i in xrange(imax):
a = a + 10
print a
Are there any ways to speed up the for/xrange loop?
Sure; the above can be
On Thu, 2010-09-02 at 16:13 +0200, Roland Koebler wrote:
Hi,
Are there any ways to speed up the for/xrange loop?
You can use psyco.
Assuming you've got a 32-bit machine.
--
http://mail.python.org/mailman/listinfo/python-list
] On Behalf Of
Nobody
Sent: Thursday, September 02, 2010 9:05 AM
To: python-list@python.org
Subject: Re: Speed-up for loops
On Thu, 02 Sep 2010 12:02:40 +0200, Michael Kreim wrote:
I was comparing the speed of a simple loop program between Matlab and
Python.
imax = 10
a = 0
for i
Philip Bloom wrote:
Uh.
Try:
Imax=10
a=0
i=0
While(iimax):
a= a+10
i=i+1
print a
I suspect you will find it is way faster than using range or xrange for
large numbers and map far more closely in the final result to what you
are doing on matlab's side. At
On Sep 2, 5:55 am, Tim Wintle tim.win...@teamrubber.com wrote:
On Thu, 2010-09-02 at 12:02 +0200, Michael Kreim wrote:
Hi,
I was comparing the speed of a simple loop program between Matlab and
Python.
Unfortunately my Python Code was much slower and I do not understand why.
The main
On 9/2/2010 8:55 AM, Tim Wintle wrote:
On Thu, 2010-09-02 at 12:02 +0200, Michael Kreim wrote:
Hi,
I was comparing the speed of a simple loop program between Matlab and
Python.
Unfortunately my Python Code was much slower and I do not understand why.
The main reason is that, under the
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