Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!zaphod.mps.ohio-state.edu!mips!gumby!lilian
From: lilian@mips.COM (Lilian Leung)
Newsgroups: comp.sys.mips
Subject: Re: How can you trap floating point errors in MIPS FORTRAN?
Message-ID: <39088@mips.mips.COM>
Date: 25 May 90 23:15:40 GMT
References: <1990May15.011508.16295@portia.Stanford.EDU>
Sender: news@mips.COM
Reply-To: lilian@mips.COM (Lilian Leung)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 48

In article <1990May15.011508.16295@portia.Stanford.EDU> dhinds@portia.Stanford.EDU (David Hinds) writes:
>There may be an obvious answer to this, but I can't find it in any of our
>manuals.  In MIPS FORTRAN, how can you test a real variable to see if it
>holds a valid real number?  I get very annoyed when my programs run for a
>long time only to tell me the answer is "NaN.000".
>
> -David Hinds
>  dhinds@popserver.stanford.edu

I have sent the following response before.  In case it got lost, here it is
again:

We have implemented a function called "setfpe" which traps the following
conditions for floating point operations:
	
        1 - Invalid Operation Condition
        2 - Divide By Zero Condition
        3 - Inexact Result Condition
        4 - Overflow Condition

Here is an example for using that function:

        integer SIGFPE,DIVIDE0
        parameter (SIGFPE=8,DIVIDE0=2)
        logical old,setfpe
        external fperror
        data a/0.0/
        old = setfpe(DIVIDE0,.true.)
        isig = signal(SIGFPE,fperror,-1)
        b = 1.0/a
        print *,b
        end

A user can specify his/her own "fperror" function.

We have also implemented a command-line flag called "-trapuv" for initializing
all local and stack variables to NaNs.  When a floating point operation on
a NaN operand occurs, the compiler takes a floating pointing exception and
dumps core.

Please contact our techical support for more details on the above
functions.


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