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Re: Math functions and rounding mode

From: Joseph Myers <joseph at codesourcery dot com>
To: Patrick McGehearty <patrick dot mcgehearty at oracle dot com>
Cc: <libc-alpha at sourceware dot org>
Date: Mon, 1 Jan 2018 16:36:28 +0000
Subject: Re: Math functions and rounding mode
Authentication-results: sourceware.org; auth=none
References: <DB6PR0801MB2053D73D0DCF65F8E6CC4AD483180@DB6PR0801MB2053.eurprd08.prod.outlook.com> <25358a9a-b47b-aaf3-00d0-31fe5befea8e@oracle.com>

On Mon, 1 Jan 2018, Patrick McGehearty wrote:

> When the current rounding mode is not FE_TONEAREST on entry to exp(),
> and if we do not change the rounding mode to FE_TONEAREST within exp(),
> then we get more 1 ulp errors according to the make check tests
> of exp(). I suspect users who care enough to try other rounding
> modes than FE_TONEAREST really care about those 1 ulp diffs.

1ulp errors in non-default rounding modes are definitely not a problem.

-- 
Joseph S. Myers
joseph@codesourcery.com

References:
- Math functions and rounding mode
  - From: Wilco Dijkstra
- Re: Math functions and rounding mode
  - From: Patrick McGehearty

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