On Sat, Nov 15, 2008 at 10:20 AM, Jason Grout
<[EMAIL PROTECTED]> wrote:
>
> pong wrote:
>>
>> I have turned some codes that I have from PARI/GP into SAGE script but
>> I find that they are order of magnitude slower than the original
>> codes. Both types of codes are complied (i.e. I have .run in PARI and
>> spyx files for SAGE) and running on the same machine.
>>
>> I am sure that's because I don't know enough of SAGE/Python to make
>> them fast (e.g. log(RDF(2)) seems to be faster than log(float(2))). In
>> general, if I want to do some simply arithmetic operations fast,
>> what's the way to go with SAGE? Is sage.ext.arith the module that I
>> should use?
>>
>> I couldn't find help on using fast_arith from the SAGE documentation
>> so any examples and pointers are appreciated.
>
>
> Posting some specific snippets that we can help with will probably get
> better answers that queries for general advice.
>
> That is curious about the log(RDF(2)) compared to log(float(2)). What
> about math.log(float(2))? That is pretty much the C log function being
> called on a C float. (You might have to import math first). Here are
> the timings:
>
> sage: a=RDF(2)
> sage: %timeit b=log(a)
> 1000000 loops, best of 3: 1.71 µs per loop
> sage: a=float(2)
> sage: %timeit b=log(a)
> 100000 loops, best of 3: 10.4 µs per loop
> sage: from math import log
> sage: %timeit b=log(a)
> 1000000 loops, best of 3: 643 ns per loop
>
By the way, math.log is also just as fast on RDF's as on
floats, at least on my OS X box (see the last two timings
below):
sage: a = RDF(2)
sage: timeit('log(a)')
625 loops, best of 3: 4.98 µs per loop
sage: a = float(2)
sage: timeit('log(a)')
625 loops, best of 3: 7.68 µs per loop
sage: from math import log
sage: a = float(2)
sage: timeit('log(a)')
625 loops, best of 3: 619 ns per loop
sage: a = RDF(2)
sage: timeit('log(a)')
625 loops, best of 3: 613 ns per loop
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