[Numpy-discussion] Psyco MA?

Francesc Alted falted at openlc.org
Wed Feb 12 05:04:03 CST 2003


Some days ago, I've also done some benchmarks on this issue, and I think
that could be good to share my results. 

I'm basically reproducing the figures of Tim, although that with a
difference still bigger in favour of Numeric for small matrix (2x2). The
benchmarks are made with a combination of Python and Pyrex (in order to test
also some functions in Numeric and numarray C API).

The figures I'm getting are, roughly:

Matrix multiplication:

In Python:
matrixmultiply (double(2,2) x double(2,)) in Numeric:    70 us
matrixmultiply (double(2,2) x double(2,)) in numarray: 4800 us

In Pyrex:
numarray multiply in Pyrex, using NA_InputArray:          620 us
numarray multiply in Pyrex, using PyObject_AsWriteBuffer: 146 us


In Python:
double(2,) in Numeric:    58 us
double(2,) in numarray: 3100 us

In Pyrex (using PyArray_FromDims):
double(2,) with Numeric:   26 us
double(2,) with numarray: 730 us

As, you can see, in pure Python, numarray has a factor of 50 (for zeros) and
up to 70 (for matrix multiply) times more overhead than Numeric. Increasing
the matrix to a 200x20 the overhead difference falls down to factor of 16
(for matrix multiply) and 50 (for zeros) always in favor of Numeric.

With Pyrex (i.e. making the C calls), the differences are not so big, but
there is still a difference. In particular, when assuming a contiguous
matrix and calling PyObject_AsWriteBuffer directly upon the object._data
memory buffer, the factor falls down to 2. Increasing the matrix to 200x20,
the overhead for zeros (using PyArray_FromDims) is the same for numarray
than Numeric (around 700 us), while multiply in Pyrex can't beat the
matrixmultiply in Numeric (Numeric is still 2 times faster).

Hope that helps. I also can send you my testbeds if you are interested in.

Francesc Alted

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