erfc failure with large numbers

[David Bateman]

Shea, Philip wrote:
> I'm a little surprised that the library routine can't handle large 
> numbers.  There are good approximations to the erfc for large numbers 
> (see Proakis, John G., Digital Communications, pg. 40, eq. (2-1-96)).  
> I have attached the output of the octave bug_report function.
>  
> octave-3.0.1.exe:4> erfc(1000)
>  ***MESSAGE FROM ROUTINE DERFC IN LIBRARY SLATEC.
>  ***POTENTIALLY RECOVERABLE ERROR, PROG ABORTED, TRACEBACK REQUESTED
>  *  X SO BIG ERFC UNDERFLOWS
>  *  ERROR NUMBER = 1
>  *
>  ***END OF MESSAGE
>  
>  ***JOB ABORT DUE TO UNRECOVERED ERROR.
> 0          ERROR MESSAGE SUMMARY
>  LIBRARY    SUBROUTINE MESSAGE START             NERR     LEVEL     COUNT
>  SLATEC     DERFC      X SO BIG ERFC UNDERF         1         1         1
>  
Yes this is not the only function that has such issues. Basically for 
the release after 3.2 we were planning to replace some of the underlying 
special function code with the GSL libraries that is maintained and 
supports larger arguments than the older unmaintained SLATEC code does.

Regards
David

-- 
David Bateman                                David.Bateman at motorola.com
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