potential error in fdlibm asin

Lindenmaier, Goetz goetz.lindenmaier at sap.com
Mon Dec 5 13:29:05 UTC 2016


does anybody know for which x 
does _not_hold?  Where 
  huge =  1.000e+300, 
  one =  1.00000000000000000000e+00
  |x| < 2**-27
I've no idea, but I need that to build a test case.

Anyways we think t=0 is fine for |x| < 2**-27 as in that range 
x = asin(x) wrt. to the preciseness of double.

If t = 0, p will evalutate to p=0, q to q=1 and thus x will be returned.

Best regards,

> -----Original Message-----
> From: core-libs-dev [mailto:core-libs-dev-bounces at openjdk.java.net] On Behalf
> Of Andrew Haley
> Sent: Montag, 5. Dezember 2016 11:10
> To: core-libs-dev at openjdk.java.net
> Subject: Re: potential error in fdlibm asin
> On 02/12/16 14:24, Lindenmaier, Goetz wrote:
> >
> > I found one copy of this code in the internet where the "else" is removed,
> > but it's not completely the same:
> > https://github.com/jerryscript-project/jerryscript/blob/master/jerry-
> libm/asin.c
> >
> > Does anybody have the knowledge to tell me what's wrong?
> > Does anybody know how to contribute a fix to netlib fdlibm?
> I think the only way to proceed with this is to find an input argument
> which is affected by this very odd code.  If there is one. does it
> give a correct or an incorrect result?  If not, we don't care and it
> can be tidied up later.
> Andrew.

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