Improve accuracy of eraStarpv() #41
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
In the relativistic correction, the term del = sqrt(1+x) - 1 is used with a rather small value of x (often 1e-8 or such). This gives inaccurate results because of the subtraction of 1 from a number very close to 1. To improve this, the right term is extended by sqrt(1+x)+1, which gives del = x / (sqrt(1+x) + 1) without a subtraction of two equally large numbers and therefore a better accuracy. This helps on i386 FPU. The test is adjusted as well.
|
@scottransom can you take a look at this with regard to whether this patch is suitable for upstream SOFA? See also #33. |
|
@scottransom - just to check, did you also pass this along to the sofa board when discussing #40 ? |
|
@scottransom just mentioned in #40 that this is a good fix, so I'll just go ahead and merge this. Probably we can just remove it again at the next SOFA release, but just in case... Thanks @olebole! |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
In the relativistic correction, the term
is used with a rather small value of
x(often 1e-8 or such). This gives inaccurate results because of the subtraction of 1 from a number very close to 1.To improve this, the right term is extended by
sqrt(1+x)+1, which giveswithout a subtraction of two equally large numbers and therefore a better accuracy. This helps
on i386 FPU.to get on all platform results that are as excellent as with the x87 FPU ;-)The test is adjusted as well.
This will fix #33.