[Numpy-discussion] Dealing with the mode argument in qr.

Charles R Harris charlesr.harris@gmail....
Tue Feb 5 23:12:58 CST 2013


On Tue, Feb 5, 2013 at 2:23 PM, Charles R Harris
<charlesr.harris@gmail.com>wrote:

> Hi All,
>
> This post is to bring the discussion of PR #2965<https://github.com/numpy/numpy/pull/2965>to the attention of the list. There are at least three issues in play here.
>
> 1) The PR adds modes 'big' and 'thin' to the current modes 'full', 'r',
> 'economic' for qr factorization. The problem is that the current 'full' is
> actually 'thin' and 'big' should be 'full'. The solution here was to raise
> a FutureWarning on use of 'full', alias it to 'thin' for the time being,
> and at some distant time change 'full' to alias 'big'.
>
> 2) The 'economic' mode serves little purpose. I propose to deprecate it
> and add a 'qrf' mode instead, corresponding to scipy's 'raw' mode. We can't
> use 'raw' itself as traditionally the mode may be specified using the first
> letter only and that leads to a conflict with 'r'.
>
> 3) As suggested in 2, the use of single letter abbreviations can constrain
> the options in choosing mode names and they are not as informative as the
> full name. A possibility here is to deprecate the use of the abbreviations
> in favor of the full names.
>
> A longer term problem is the divergence between the numpy and scipy
> versions of qr. The divergence is enough that I don't see any easy way to
> come to a common interface, but that is something that would be desirable
> if possible.
>
> Thoughts?
>
>
bfroehle has suggested the names

1. complete: Q is a M-by-M matrix, i.e. a complete orthogonal basis.
2. reduced: Q is a M-by-K matrix.
3. r: Only return R
4. raw: Return Householder reflectors Q and TAU

Chuck
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