Re: [Numpy-discussion] Numpy x Matlab: some synthetic benchmarks

[Andrew S. <str...@as...>]

Paulo J. S. Silva wrote:

>Em Qua, 2006-01-18 =C3=A0s 11:15 -0700, Travis Oliphant escreveu:
>
> =20
>
>>Will you run these again with the latest SVN version of numpy.   I=20
>>couldn't figure out why a copy was being made on transpose (because it=20
>>shouldn't have been).  Then, I dug deep into the PyArray_FromAny code=20
>>and found bad logic in when a copy was needed that was causing an=20
>>inappropriate copy.
>>
>>I fixed that and now wonder how things will change.  Because presumably=
,=20
>>the dotblas function should handle the situation now...
>>
>>   =20
>>
>
>Good work Travis :-)
>
>Tests    x.T*y   x*y.T     A*x     A*B   A.T*x    half    2in2
>
>Dimension: 5
>Array   0.9000  0.2400  0.2000  0.2600  0.7100  0.9400  1.1600
>Matrix  4.7800  1.5700  0.6200  0.7600  1.0600  3.0400  4.6500
>NumArr  3.2900  0.7400  0.6800  0.7800  8.4800  7.4200 11.6600
>Numeri  1.3300  0.3900  0.3100  0.4200  0.7900  0.6800  0.7600
>Matlab  1.88    0.44    0.41    0.35    0.37    1.20    0.98
>
>Dimension: 50
>Array   9.0000  2.1400  0.5500 18.9500  1.4100  4.2700  4.4500
>Matrix 48.7400  3.9200  1.0100 20.2000  1.8000  6.5000  8.1900
>NumArr 32.3900  2.6800  1.0000 18.9700 13.0300  8.6300 13.0700
>Numeri 13.1000  2.2600  0.6500 18.2700 10.1500  1.0400  3.2600
>Matlab 16.98    1.94    1.07   17.86    0.73    1.57    1.77
>
>Dimension: 500
>Array   1.1400  9.2300  2.0100 168.2700  2.1800  4.0200  4.2900
>Matrix  5.0300  9.3500  2.1500 167.5300  2.1700  4.1100  4.4200
>NumArr  3.4400  9.1000  2.1000 168.7100 21.8400  4.3900  5.8900
>Numeri  1.5800  9.2700  2.0700 167.5600 20.0500  3.4000  4.6800
>Matlab  2.09    6.07    2.17   169.45    2.10     2.56    3.06
>
>Note the 10-fold speed-up for higher dimensions :-)
>
>It looks like that now that numpy only looses to matlab in small
>dimensions. Probably, the problem is the creation of the object to
>represent the transposed object. Probably Matlab creation of objects is
>very lightweight (they only have matrices objects to deal with).
>Probably this phenomenon explains the behavior for the indexing
>operations too.
>
>Paulo
>
>
> =20
>
Here's an idea Fernando and I have briefly talked about off-list, but=20
which perhaps bears talking about here: Is there speed to be gained by=20
an alternative, very simple, very optimized ndarray constructor? The=20
idea would be a special-case constructor with very limited functionality=20
designed purely for speed. It wouldn't support (m)any of the fantastic=20
things Travis has done, but would be useful only in specialized use=20
cases, such as creating indices.

I'm not familiar enough with what the normal constructor does to know if=20
we could implement something, (in C, perhaps) that would do nothing but=20
create a simple, contiguous array significantly faster than what is=20
currently done. Or does the current constructor create a new instance=20
about as fast as possible? I know Travis has optimized it, but it's a=20
general purpose constructor, and I'm thinking these extra features may=20
take some extra CPU cycles.

Cheers!
Andrew