Re: [ublas] CVS updates (please update and report regressions)

From: Hugo Duncan (hugoduncan_at_[hidden])
Date: 2007-03-17 14:41:57

Hello Karl,

>>> Any chance of getting the leading dimension fixed in the bindings
>>> traits?
>>>
>>> http://www.nabble.com/Lapack-bindings-t3237071.html
>>> http://www.nabble.com/ublas-traits-bug-----leading_dimension-p9469619
>>> .html

> In my opinion, there is no error in the bindings traits classes.
> To be sure, can someone tell me what the difference is between size_m
> and size_M? The leading dimension is the number of rows of ublas::matrix
> for column_major matrices.

The nearest I can find to a canonical description of leading dimension  
(LDA):
   http://www.netlib.org/lapack/lug/node116.html

Although this is more informative.
http://icl.cs.utk.edu/lapack-forum/viewtopic.php?t=217&sid=79b90021ff88b6cc1d18db411b2f7ad4

As I am sure you are all too aware, and you state above, these all show  
the leading dimension as the number of rows.  So far I think we agree.

I find the use of m and M non-intuitive, but believe:

size_m = minor size
size_M = major size

For a column major matrix, I believe the major size is the number of  
columns, so the leading dimension should be the minor size.  The debugger  
leads me to confirm these beliefs.  But I get thoroughly confused by major  
and minor sizes, so I would not be too categoric in stating this.

> Note that for row_major matrices, lapack bindings do not work.

Agreed.

Thanks for looking at this,

Hugo