HUGE_VALF和INFINITY常量之间的区别 [英] Difference Between HUGE_VALF and INFINITY Constants

问题描述

在OpenCL中，有两个浮点数学常量表示无穷大。其中之一就是 INFINITY 。另外， HUGE_VALF ，评估为无穷大。

这两者有什么区别？这是什么意思，评估无穷？

解决方案

HUGE_VALF 是一个传统名称，允许不支持无穷的浮点系统。例如，C标准指定在某些溢出情况下返回 HUGE_VALF 。当C实现不支持无穷时， HUGE_VALF 将是最大的可表示值。当一个实现支持无限时， HUGE_VALF 将是无穷的。 C标准仍然允许这样做，而且我认为有一些实现仍然不支持无穷。

OpenCL使用IEEE 754（或多或少），所以它有无穷大，所以 HUGE_VALF 是无穷大。通过定义 HUGE_VALF ，OpenCL有助于支持旧C代码移植到OpenCL。

关于 HUGE_VALF 计算结果为+ infinity但是 INFINITY 是浮点类型的常量表达式，表示正或无符号无穷大，I会怀疑这是否意图允许一些运行时准备 HUGE_VALF （例如，将其表示为 1./0。）。但是，文档也表示 HUGE_VALF 是一个积极的浮点常量表达式。在余额上，这让我觉得措辞简单一点，而且 HUGE_VALF 和 INFINITY 是等效的。

In OpenCL, there are two floating point math constants that represent infinity. One of them is simply INFINITY. The other, HUGE_VALF, "evaluates to" infinity.

What is the difference between these two? What does it mean to "evaluate to" infinity?

解决方案

HUGE_VALF is a legacy name that allows for floating-point systems that did not support infinities. For example, the C standard specifies that HUGE_VALF be returned in certain overflow cases. When a C implementation did not support infinities, HUGE_VALF would be the largest representable value. When an implementation did support infinities, HUGE_VALF would be infinity. The C standard still allows this, and I suppose there are some implementations around that still do not support infinities.

OpenCL uses IEEE 754 (more or less), so it does have infinities, so HUGE_VALF is infinity. By defining HUGE_VALF, OpenCL helps to support old C code being ported to OpenCL.

Regarding the wording that says "HUGE_VALF evaluates to +infinity" but INFINITY is "A constant expression of type float representing positive or unsigned infinity", I would wonder whether that is intended to allow for some run-time preparation of HUGE_VALF (e.g., expressing it as 1./0.). However, the documentation also says that HUGE_VALF is "A positive float constant expression." On the balance, that makes me think the wording is simply a bit sloppy, and that HUGE_VALF and INFINITY are equivalent.

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