Hi Regina, On Monday, 2009-04-06 10:11:43 +0200, Regina Henschel wrote:
> I'm working to increase accuracy of ScArcCosHyp(). The function acosh is
> part of C99 but not provided by MSVC. Therefore I have written the
> ersatz in sal\rtl\source\math.cxx
Nice.
> double SAL_CALL rtl_math_acosh( double fX ) SAL_THROW_EXTERN_C()
> {
> double fZ = fX - 1.0;
It might be necessary to declare fZ as volatile here. We already had
such a case that the gcc compiler attempted to overoptimize things, see
comments in rtl_math_log1p().
> if ( fX == 1.0)
> return 0.0;
> else if (fX < 1.1)
> return rtl_math_log1p(fZ+sqrt(fZ*fZ+2.0*fZ));
> else if ( fX < 1.25e7)
> return log(fX+sqrt(fX*fX-1.0));
> else
> return log(2.0*fX);
> }
>
> The function acosh is not defined for x<1. The function ScArcCosHyp()
> pushes an IllegalArgument and do not call acosh in that cases.
>
> Do I need any kind of error handling in my rtl_math_acosh? The function
> acosh might be called from somewhere else, not only from ScArcCosHyp.
Yes, please return a NaN in that case:
double fResult;
rtl::math::setNan( &fResult );
return fResult;
Calc's interpreter will handle a NaN result automatically.
Eike
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