operand order overly important in sparse <-> dense operations

scalala / Scalala

Scalala has been superseded by dlwh/breeze. Scalala is a high performance numeric linear algebra library for Scala, with rich Matlab-like operators on vectors and matrices; a library of numerical routines; support for plotting.

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operand order overly important in sparse <-> dense operations #3

Open dramage opened 13 years ago

dramage commented 13 years ago

Reported by logophobia on the mailing list:

If you multiply a sparse vector with a dense vector then the ordering matters a lot. The sparse vector "knows" which items not to multiply (since they are zero). If you multiply (dense * sparse) then it takes much more time then (sparse * dense). I think this would probably be an easy optimization to add. Same think for the "dot" operation (and prehaps others)

dramage commented 13 years ago

This is fixed for dot products as of https://github.com/scalala/Scalala/commit/6f9a1283d0e1b70642720144f56731d978a8e1b5

What remains is keeping the correct static type through the operations. E.g. dense + sparse should return dense (statically) whereas dense :* sparse should return sparse (statically).