tree 6b3f48c5794e3b2cddb5e42471ededa02d1cc63a
parent 0a30117489d9283e19fce95521785a833f91a7c4
author William Rucklidge <wjr@google.com> 1520023074 -0800
committer William Rucklidge <wjr@google.com> 1520026399 -0800

Improve threading in covariance.

Covariance computation wants to do a triangular iteration but as a
single loop. Right now it iterates over a square and does nothing half
the time, which is inefficient and has bad worst-case threading
performance. This adds a utility that allows waste-free linear iteration
over a triangle.

Change-Id: I881d5683c65882f87dc2b5f8449a855d22ace755