[SciPy-Dev] Fwd: Re: [Numpy-discussion] Dealing with the mode argument in qr.

Nathaniel Smith njs@pobox....
Tue Feb 5 23:58:26 CST 2013


Dear scipy-dev,

What do you are think of these names for the qr modes? It would be nice if
scipy and numpy could get these aligned (right now they have different
defaults and multiple modes with the same name but different semantics...).

-n
---------- Forwarded message ----------
From: "Charles R Harris" <charlesr.harris@gmail.com>
Date: 5 Feb 2013 21:13
Subject: Re: [Numpy-discussion] Dealing with the mode argument in qr.
To: "numpy-discussion" <numpy-discussion@scipy.org>
Cc:



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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