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Ublas :

From: christopher diggins (cdiggins_at_[hidden])
Date: 2005-06-12 11:41:15

>From the FAQ:

"The first assigned seemes to be at least twice as fast as the second
assignement, although the same algorithm is used. Why? UBLAS always expects
that the right hand side of an expression can have common storage with the
left hand side, i.e. that there is aliasing. Thus uBLAS first evaluates the
right hand side into a temporary vector and then applies the changes to the
left hand side."

I mentioned this before, and I'll say it again: A straightforward
implementation of += and -= is not affected by aliasing. This is trivial to
fix. I find it unacceptable that the library can not do such a simple task

Christopher Diggins