ISO/IEC TS 18661-4:2025 PDF

Name: ISO/IEC TS 18661-4:2025 — Programming languages, their environments, and system software interfaces — Floating-point extensions for C — Part 4: Supplementary functions
SKU: ISO/IEC TS 18661-4:2025
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Programming languages, their environments, and system software interfaces — Floating-point extensions for C — Part 4: Supplementary functions

Название (английский):

ISO/IEC TS 18661-4:2025

Programming languages, their environments, and system software interfaces — Floating-point extensions for C — Part 4: Supplementary functions

Статус документа:: Действующий
Формат:: Электронный (PDF)
Количество страниц:: 13
Дата публикации:: 14 марта 2025 г.
Издание:: ISO/IEC TS 18661 edition 2 version 1
ICS:: 35.060

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Описание (английский):

This document specifies extensions to programming language C to include functions corresponding to operations specified and recommended in ISO/IEC 60559, but not supported in ISO/IEC 9899:2024 (also referred to as C23).

Abstract

Похожие стандарты

Упомянутые в описании и другие стандарты ISO

Overview

ISO/IEC TS 18661-4:2025 defines supplementary floating-point extensions for the C programming language. Published by ISO and IEC, this technical specification addresses the need for additional floating-point operations in C, corresponding to those defined in IEEE 754 (ISO/IEC 60559), which are not covered in the main C standard, ISO/IEC 9899:2024 (C23). The new extensions focus on advanced mathematical and numerical functions valuable for a wide range of technical, scientific, and engineering applications.

The primary goals of this standard are to enhance numerical reliability, provide precise computation tools, and support improved portability for C programs that require advanced floating-point functionality. By implementing these supplementary functions, both software developers and system architects can ensure consistent behavior and compliance with international floating-point arithmetic standards.

Key Topics

Reduction Functions ()

Provide sum, sum of absolute values, sum of squares, and dot product (sumprod) for arrays.
Enable accurate and efficient vector computations, supporting both binary and decimal floating-point types.
Offer scaled product and related operations (scaled_prod, scaled_prodsum, scaled_proddiff) to prevent overflow and underflow during intermediate computations.

Augmented Arithmetic Functions ()

Introduce augmented arithmetic as recommended by IEEE 754, including the well-known twoSum and twoProduct operations.
Functions return both the computed value and the error term, assisting in double-double arithmetic for increased precision.

Conformance and Integration

Implementations must use specific macros to indicate support: __STDC_IEC_60559_FUNCS_REDUCTION__ and __STDC_IEC_60559_FUNCS_AUGMENTED_ARITHMETIC__.
Designed as conditional standard library extensions, ensuring backward compatibility with C23 environments.

Precision and Exception Handling

Functions are specified to minimize intermediate loss of precision.
Floating-point exceptions are tightly defined for predictable behavior across platforms.

Applications

The supplementary floating-point functions in ISO/IEC TS 18661-4:2025 serve a variety of practical and advanced use cases:

Scientific Computing

Reliable implementations for computing sums, dot products, and sum-of-squares, critical for data analysis, simulations, and scientific modeling.
Example: Calculating large factorial products in quantum physics or statistical algorithms without intermediate overflow.

Numerical Libraries and High-Performance Computing

Use of reduction and augmented arithmetic enables increased precision in iterative numerical methods and linear algebra routines.
Double-double arithmetic is made easier and more robust, benefiting environments without native hardware support for high-precision types.

Embedded and Safety-critical Systems

Ensures conforming implementations in resource-constrained or safety-sensitive contexts, with predictable exception and error signaling.

Financial Calculations

Support for decimal floating-point arithmetic meets the needs of applications that demand exact decimal results.

Related Standards

ISO/IEC 9899:2024 (C23): The core standard for the C programming language, with which these extensions are fully compatible.

ISO/IEC 60559:2020: Specifies floating-point arithmetic following IEEE 754, forming the basis for the operations and numeric behaviors required by this extension.

Other ISO/IEC TS 18661 parts: Additional documents in the 18661 series further extend floating-point support in C.

IEEE 754-2019: The updated international standard for floating-point arithmetic, referenced in the design of the augmented arithmetic operations.

By adhering to ISO/IEC TS 18661-4:2025, developers and implementers of C can create portable, standards-compliant applications that harness advanced floating-point functions for greater accuracy, consistency, and performance in critical computations.

ISO/IEC TS 18661-4:2025 PDF

Abstract

Похожие стандарты

Overview

Key Topics

Applications

Related Standards

Технические детали

BS ISO/IEC 60559:2020

Floating-point arithmetic

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