Preface

The HP-UX Floating-Point Guide describes how floating-point arithmetic is implemented on HP 9000 systems and discusses how ­floating-point behavior affects the programmer. This book provides information useful to any programmer writing or porting floating-point-intensive programs.

We recommend that you start with Chapter 1 “Introduction”, which not only provides an overview of floating-point principles but also provides important information about HP-UX math libraries.

If you are unfamiliar with floating-point issues, you should go next to Chapter 2 “Floating-Point Principles and the IEEE Standard for Binary Floating-Point Arithmetic” and Chapter 3 “Factors that Affect the Results of Floating-Point Computations”. Chapter 2 “Floating-Point Principles and the IEEE Standard for Binary Floating-Point Arithmetic” provides an overview of the IEEE Standard for Binary Floating-Point Arithmetic, which constitutes the foundation for many floating-point architectures, including Hewlett- Packard's. For more specific information about the standard, contact the IEEE Standards Board. Chapter 3 “Factors that Affect the Results of Floating-Point Computations” describes the many factors that can cause floating-point computations to produce unexpected results.

If you already understand floating-point issues, you may want to go directly to Chapter 4 “HP-UX Math Libraries on HP 9000 Systems” and the subsequent chapters and appendixes, which provide specific information about floating-point behavior on HP 9000 systems and about the libraries and facilities available on these systems.

If you have the HP FORTRAN/9000 (FORTRAN 77) compiler, all of the sample programs in this manual are online, in the directory /opt/fortran/lib/demos/FPGuide. In the manual, a comment in the text of each sample program indicates the path name of the program.

Comments

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Audience

This manual is written for application developers who write programs that perform mathematical operations. It assumes a basic knowledge of the HP-UX operating system and of a high-level programming language such as C or Fortran.

Summary of Technical Changes

This edition of the HP-UX Floating-Point Guide describes the following changes to the HP-UX math libraries at Release 10.30.

The PA1.0 math libraries are no longer supported at HP-UX Release 10.30. The math libraries provided in the /usr/lib directory support both PA1.1 and PA2.0 systems.

A version of the BLAS library tuned for optimal performance on PA2.0 systems is provided in the directory /opt/fortran90/lib/pa2.0/libblas.a (for HP Fortran 90) or /opt/fortran/lib/pa2.0/libblas.a (for HP FORTRAN/9000, the Fortran 77 product).

The vector library, libvec.a, is obsolete. It is supplied for backward compatibility but has been moved to the directory /opt/fortran/old/lib.

At Release 10.30, the C math library implements several new functions approved by the ISO/ANSI C committee for inclusion in the C9X draft standard, and eliminates support for several functions supported neither by the C9X standard nor by the XPG4.2 standard.

The following C library functions are no longer supported:

The C library supports the following new functions and macros:

The following C library functions are now implemented as macros:

The value of HUGE_VAL has changed from "The maximum non-infinity value of a double-precision floating-point number" to positive infinity.

Related Documentation

The IEEE Standard for Binary Floating-Point Arithmetic (ANSI/IEEE Std 754-1985) is the essential reference for developers of floating-point applications. To obtain a copy, write to the IEEE Standards Board, 345 East 47th Street, New York, NY 10017, USA.

The document ANSI/IEEE Std 754-1985, entitled "IEEE Standard for Binary Floating-Point Arithmetic," was also published in ACM SIGPLAN Notices 22(2), pp. 9 - 25, Feb. 1987.

The international version of the standard is Binary floating-point arithmetic for microprocessor systems, second edition (IEC 559:1989).

Information on HP-UX programming languages and tools is available in both online and hardcopy format. The following online guides are available through the HP Help System if you have the relevant compilers or tools:

You may also refer to the following hardcopy documents:

To order manuals, call HP DIRECT at 1-800-637-7740. Outside the USA, please contact your local sales office.