Path: utzoo!utgpu!watserv1!watmath!att!att!pacbell.com!mips!zaphod.mps.ohio-state.edu!usc!ucsd!ucbvax!F.ADELAIDE.EDU.AU!DDAVID
From: DDAVID@F.ADELAIDE.EDU.AU
Newsgroups: comp.sys.sgi
Subject: Re: Another C compiler bug
Message-ID: <901105134647.1282@F.ADELAIDE.EDU.AU>
Date: 5 Nov 90 19:46:47 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 49

Martin Fong writes:
>I get the following results on the following MIPS-based systems:
>
>	RISC ULTRIX 3.0			7e-7 = 0.000000
>	SGI IRIX 3.2			7e-7 = 0.000000
>	MIPS OS 1.0			7e-7 = 0.000001
>
>Looks like yet another compiler bug which MIPS has fixed but DEC and
>SGI have not yet picked up.
>

This is another example of the following:

This test program

main() {
  float x;
  while (1) {
    printf("input x : ");
    scanf("%f", &x);
    printf("x = %f -> %.0f\n", x,x);
  }
}

produces the following output (Irix 3.3.1) :
x = 0.2 -> 0
x = 0.6 -> 0	        ??
x = 0.95 -> 0		??
x = 0.99 -> 1		????
x = 1.2 -> 1
x = 1.6 -> 2
x = 2.2 -> 2
x = 2.6 -> 3

x = -1.6 -> -2
x = -1.20 -> -1
x = -0.99 -> -1		????
x = -0.90 -> 0		??
x = -0.60 -> 0		??
x = -0.2 -> 0

so you can see that printf is not consistent in rounding to the nearest
number for floating point numbers between -1 and 1. 

A minor bug but annoying. I hope it is fixed in the next release.

Regards,
David Netherway,
Australian Cranio-Facial Unit