convert RDF/CDF matrices to numpy

[jasongrout]

This patch makes the following work:

            sage: import numpy
            sage: m = matrix(RDF, 2, range(6)); m
            [0.0 1.0 2.0]
            [3.0 4.0 5.0]
            sage: numpy.array(m)                  
            array([[ 0.,  1.,  2.],
            [ 3.,  4.,  5.]])
            sage: numpy.array(m).dtype            
            dtype('float64')
            sage: m = matrix(CDF, 2, range(6)); m
            [  0 1.0 2.0]
            [3.0 4.0 5.0]
            sage: numpy.array(m)                  
            array([[ 0.+0.j,  1.+0.j,  2.+0.j],
            [ 3.+0.j,  4.+0.j,  5.+0.j]])
            sage: numpy.array(m).dtype            
            dtype('complex128')

            sage: import numpy
            sage: b=numpy.array(a); b
            array([[ 0,  1,  2,  3],
                   [ 4,  5,  6,  7],
                   [ 8,  9, 10, 11]])
            sage: b.dtype
            dtype('int64')
            sage: b.shape
            (3, 4)

CC: @rbeezer

Component: linear algebra

Author: Jason Grout

Reviewer: Rob Beezer

Merged: sage-4.4.2.alpha0

Issue created by migration from https://trac.sagemath.org/ticket/8719

[jasongrout]

Author: Jason Grout

[jasongrout]

comment:5

rbeezer: it seems like you could naturally review this. It just adds a numpy-specific magic method for conversion.

[rbeezer]

comment:6

Hi Jason,

So you have defined a new method "__array__" for a Sage matrix object. When somebody calls numpy.array(a) for a Sage matrix a then this __array__ method gets called (and this is in effect just the numpy() method of a Sage matrix)? In other words, the numpy.array() method has an expanded reportoire and now "knows" how to deal with a Sage matrix object?

If so, could you say so? The line __array__=numpy all by itself looks really mysterious with no documentation. And the new doctests say "you could use numpy" - when Sage is really doing the heavy-lifting? It sounds like numpy is doing the work, when this is not a standard behavior of numpy.

So I'm suggesting maybe this seemingly circular arrrangement (modify Sage matrices, so numpy can deal with them, using a Sage function to convert to a numpy array) could be better explained so nobody messes it up or gets too confused. With the added code and the added doctests all together, I think I was able to figure this out - otherwise it would have been a head-scratcher.

Rob

[jasongrout]

Attachment: trac_8719-numpy-conversion.patch.gz

[jasongrout]

comment:7

I updated the docs.

[rbeezer]

comment:8

Replying to @jasongrout:

I updated the docs.

Looks good! I'll finish this tomorrow night.

[rbeezer]

comment:9

Looks good, builds and passes all tests, documentation builds without warnings.

The added documentation looks great.

Positive review.

[rbeezer]

Reviewer: Rob Beezer

[sagetrac-mvngu]

Merged: sage-4.4.2.alpha0