| Phil Carmody on Wed, 05 Oct 2005 15:23:10 +0200 |
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| Re: Fwd: Incorrect conversion of unnormalized IEEE doubles |
--- kynn@panix.com wrote: > > print Math::Pari::PARI( POSIX::DBL_MIN()/2 ) > > 1.668805393880401037E-308 > > > > ...which is actually POSIX::DBL_MIN*(3/4). This represents a relative > > error of 50%, which is far from negligible. > > > > It appears that Math::Pari::PARI is converting numbers of the form > > > > POSIX::DBL_MIN()/2**$n > > > > (where $n is a positive integer) into numbers of the form > > > > POSIX::DBL_MIN()*((2**$n)-1)/(2**(-$n-1)) Is division by 2 handled as a special case involving shifts, as it sounds like a signed shift preserving a top bit where an unsigned shift should be performed. Phil () ASCII ribbon campaign () Hopeless ribbon campaign /\ against HTML mail /\ against gratuitous bloodshed [stolen with permission from Daniel B. Cristofani] __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com