tree 706fa150d3427241dbdeeb38964b8a6aa0e7aff7
parent d707d84b126d103b7e6bbef47d53a9c0d3bb0609
author Herb Derby <herb@google.com> 1684961387 -0400
committer SkCQ <skcq-be@skia-corp.google.com.iam.gserviceaccount.com> 1685116952 +0000

Calculate a very accurate discriminant

Calculate the discriminant in the ordinary manner. Check
for too much cancellation if B^2 and AC are too close.
If they are too close, then track the rounding error while
recalculating the discriminant, and add rounding error
back in. Tests included.

Change-Id: If2a04eb5c663ffe05aa90df9116796bc5f5d7a64
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/703078
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>