Butterfly matrix compress with blocks of elements?

[mdschroer]

Is building a butterfly matrix from blocks of elements supported? It looks like it is supported by ButterflyPACK, but as best as I can tell it hasn't yet been implemented in the STRUMPACK wrapper.

I can save a little bit of calculations with my kernel by computing a block at a time, as opposed to element by element. Do you expect the butterfly construct_from_elements to support block-by-block construction in the future?

Thanks!

[liuyangzhuan]

@pghysels any thought on this? I thought we already have it in strumpack sparse matrix interface, but maybe not yet for the dense interface?

[pghysels]

Apologies for the delay, yes it is supported:

STRUMPACK/src/HODLR/ButterflyMatrix.hpp

Line 124 in d64fa98

void compress(const elem_blocks_t& Aelem);

elem_blocks_t is defined here:

STRUMPACK/src/HODLR/HODLRMatrix.hpp

Line 97 in d64fa98

using elem_blocks_t = typename std::function

you can ignore the ExtractionMeta argument.

[mdschroer]

Ah gotcha! I guess that it isn't implemented in the structured interface (that I had been using), but is in the ButterflyMatrix class directly? I'll switch to using the ButterflyMatrix class.

Thanks guys!

[pghysels]

I think this one:
https://portal.nersc.gov/project/sparse/strumpack/v7.2.0/namespacestrumpack_1_1structured.html#a93b718a88093b1cb9769a28eb04c6b9a

[mdschroer]

Hmm. When I try to build a butterfly matrix using the structured interface and block extraction, I get a std::logic_error "Not implemented yet". The same code works fine with element-by-element extraction.

For reference, my matrix is a complex, with non-square shape.

If the situation isn't immediately apparent, I can put together some reproducer code.

Thanks!

[liuyangzhuan]

Yes, please post some example code for the ease of diagnosis.

…

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[pghysels]

It looks like that exception is coming from

STRUMPACK/src/structured/StructuredMatrix.cpp

Line 951 in d64fa98

throw std::logic_error("Not implemented yet.");

The functionality should be there for ButterflyMatrix (including complex and non-square), but just not added to the StructuredMatrix interface.
I don't have time to do that this week. I'll try next week.
You could try the class ButterflyMatrix directly:

STRUMPACK/src/HODLR/ButterflyMatrix.hpp

Line 123 in d64fa98

void compress(const delem_blocks_t& Aelem);