[boost] ublas questions

Subject: [boost] ublas questions
From: markus2004x (markus2004x_at_[hidden])
Date: 2010-01-05 02:06:38

Hi.

Happy new year!

I have couple of questions on uBlas. 

1) On the boost user guide I read:
"However unbounded_array is aimed at optimal performance. Therefore
unbounded_array does not model a Sequence like std::vector does". 
I do not quite understand this statement. An std::vector is memory
contiguous and access happens by offset. How can an unbounded beat this?

2) In the matrix<> template class I cannot find the concept of leading
dimension. E.g. in a row major matrix 3x3 matrix the lead dimension could be
4, meaning that in reality I have a 3x4 matrix, but I just use a 3x3 (i.e. I
have some slack at the end of each row). Is there a way to specify it? This
is the way BLAS and LAPACK are designed, and it becomes particularly
important when using hi-performance implementation of BLAS on x86, like
Intel MKL, which require 16-byte alignment of each row. I thought about
allocating a larger matrix, and then taking a range on it, but that does not
seem the natural thing to do.

Thanks a lot.

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