Thu, 19 Nov 1992 07:55:41 GMT

Related articles |
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IEEE arithmetic handling jim@meiko.co.uk (1992-11-11) |

Re: IEEE arithmetic handling tmb@arolla.idiap.ch (1992-11-16) |

Re: IEEE arithmetic handling eggert@twinsun.com (1992-11-16) |

Re: IEEE arithmetic handling bill@amber.csd.harris.com (1992-11-16) |

Re: IEEE arithmetic handling jlg@cochiti.lanl.gov (1992-11-17) |

Re: IEEE arithmetic handling eggert@twinsun.com (1992-11-17) |

Re: IEEE arithmetic handling tmb@arolla.idiap.ch (1992-11-18) |

Re: IEEE arithmetic handling bart@cs.uoregon.edu (1992-11-19) |

Re: IEEE arithmetic handling bill@amber.csd.harris.com (1992-11-20) |

Re: IEEE arithmetic handling bill@amber.csd.harris.com (1992-11-20) |

Re: IEEE arithmetic handling Dik.Winter@cwi.nl (1992-11-23) |

Re: IEEE arithmetic handling bright@nazgul.uucp (Walter Bright) (1993-01-07) |

Newsgroups: | comp.compilers |

From: | bart@cs.uoregon.edu (Barton Christopher Massey) |

Organization: | University of Oregon Computer and Information Sciences Dept. |

Date: | Thu, 19 Nov 1992 07:55:41 GMT |

Keywords: | Fortran, arithmetic |

References: | 92-11-041 92-11-097 |

eggert@twinsun.com (Paul Eggert) writes:

*> But that conflicts with IEEE Std 754-1985, section 5.6, which requires*

*> that converting a number from binary to decimal and back be the identity*

*> if the proper precision and rounding is used. The Fortran standard says*

*> -0.0 must be output as 0.0; this loses information.*

This and other recent similar comments about compilers and IEEE reminded

me of this note from the back of a recent technical report here (How To

Read Floating Point Numbers Accurately, William D. Clinger, University of

Oregon CIS-TR-90-01, June 1990)

The IEEE standard explicitly states that, in high level

languages, the destination of an arithmetic operation

may be determined by the compiler, and hence may be

beyond the control of programmers. In other words, the

compiler -- not the programmer who uses the compiler --

is regarded as the client of the standard. Thus the

error bounds guaranteed by the IEEE standard may not be

relied upon by programmers who work in high level

languages.

Modulo arguments about whether FORTRAN is a high-level language :-), it

seems to me that this pretty much answers the question of whether FORTRAN

arithmetic is IEEE compliant. It's not, but it needn't be, and it may be

unrealistic to expect it to be, given the goals of HLL design.

Bart Massey

bart@cs.uoregon.edu

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