Re: uBLAS Matrix Multiplication

From: John Lloyd (yg-boost-users_at_[hidden])
Date: 2002-11-06 16:58:14

Hickman, Greg wrote:

> Why isn't there an overloaded
> 
> matrix_expression
> operator* (const matrix_expression&, const matrix_expression&);
> 
> for peforming matrix multiplication?
> 
> Greg Hickman
> 
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I think it has something to do with the fact that expression templates can 
be very inefficient for certain chained operations, e.g., A * B * v, where 
A and B are matrices and v is a vector.

Suppose you have a  matrix expression like A = B * C * D.  Using expression 
templates, this could result in an order n^5 time complexity as opposed to 
order n^3 complexity.