kokkos / kokkos/stdBLAS

vector_sum_of_squares: Only rescale for floating-point numbers

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Dominant language
C++
Stars
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Forks
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Description

It turns out std::linalg has a couple small wording issues.

https://github.com/kokkos/stdBLAS/issues/308

The one that practically matters for implementations is LWG 4302.

https://cplusplus.github.io/LWG/lwg-active.html#4302

The reference implementation of vector_sum_of_squares must be fixed.

  1. The default algorithm should not attempt rescaling. (Don't try to rescale integers.)
  2. Constrain the rescaling algorithm to floating-point numbers.

If LWG 4302 is accepted, that would also make it permissible to use the most recent (post-2021) xLASSQ algorithm, as the scaling factor would no longer be required to be the max absolute value. 

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reading the reference implementation of vector_sum_of_squares and the LWG 4302 discussion. Check how the default algorithm handles rescaling and how the rescaling algorithm is constrained; done means integers are not rescaled by default and rescaling is limited to floating-point numbers.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
data
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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