[HN Gopher] Herbie: Automatically Improving Floating Point Accuracy
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       Herbie: Automatically Improving Floating Point Accuracy
        
       Author : lelf
       Score  : 93 points
       Date   : 2020-08-06 09:40 UTC (13 hours ago)
        
 (HTM) web link (herbie.uwplse.org)
 (TXT) w3m dump (herbie.uwplse.org)
        
       | contravariant wrote:
       | It doesn't seem to be doing too well on log(1+x). It does
       | correctly identify that the Taylor expansion is more accurate for
       | small x (although in my opinion it switches back to log(1+x) a
       | bit too soon for positive x), however it doesn't seem to take
       | into account the essential singularity at x=-1 and keeps using
       | the Taylor series for negative values all the way up to x=-1
       | leading to horrendous accuracy.
        
       | vii wrote:
       | They made a related project - http://herbgrind.ucsd.edu/ - a tool
       | that can automatically find floating point issues in real
       | programs. You can also annotate the region you're interested in
       | with herbgrind on/off controls.
       | 
       | Unfortunately - once you know you have a floating point problem,
       | tracking it down and fixing it may be easy. Not realising it, you
       | won't use these tools and the program will do the wrong thing :)
        
         | pavpanchekha wrote:
         | Very true. Floating point bugs are hard to find, because
         | there's often no way to compute a more accurate answer.
         | Herbgrind was our attempt at helping track down a _root cause_
         | once you knew floating point was the problem---that might be
         | the case if, for example, you changed from double to single
         | precision and suddenly the result was way off. But Herbgrind is
         | pretty high overhead; you 'd want some other tool to tell you
         | that floating point was a problem to begin with.
        
       | jonnycomputer wrote:
       | The natural application of this is in a code-inspection plugin
       | for an IDE. Pretty cool tool!
        
         | pavpanchekha wrote:
         | There used to be GHC and Rust plugins. I don't know much about
         | building IDE plugins, but I agree it'd be a great use of
         | Herbie.
        
       | ImaCake wrote:
       | This seems like a great tool for certain statistical
       | applications. I am learning a bit about the controversey
       | surrounding extremely small p-values in Genome Wide Association
       | Studies (think a million _n_ ANOVA) and machine precision. I
       | guess tools like this would be very useful to make sure your
       | statistical tests can more accurately calculate p-values
       | approaching the limits of machine precision.
        
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       (page generated 2020-08-06 23:00 UTC)