This is the mail archive of the
mailing list for the glibc project.
Re: IEEE128 binary float to decimal float conversion routines
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Steven Munroe <munroesj at linux dot vnet dot ibm dot com>
- Cc: Christoph Lauter <christoph dot lauter at lip6 dot fr>, "Paul E. Murphy" <murphyp at linux dot vnet dot ibm dot com>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>, Steve Munroe <sjmunroe at us dot ibm dot com>, Tulio Magno Quites Machado Filho <tuliom at linux dot vnet dot ibm dot com>, Michael R Meissner <mrmeissn at us dot ibm dot com>
- Date: Sat, 19 Dec 2015 16:40:18 +0000
- Subject: Re: IEEE128 binary float to decimal float conversion routines
- Authentication-results: sourceware.org; auth=none
- References: <564A16D5 dot 3020105 at linux dot vnet dot ibm dot com> <alpine dot DEB dot 2 dot 10 dot 1511161803500 dot 30498 at digraph dot polyomino dot org dot uk> <564A53CE dot 8080500 at lip6 dot fr> <alpine dot DEB dot 2 dot 10 dot 1511162234340 dot 32387 at digraph dot polyomino dot org dot uk> <1450473096 dot 8390 dot 75 dot camel at oc7878010663> <alpine dot DEB dot 2 dot 10 dot 1512182118350 dot 11373 at digraph dot polyomino dot org dot uk> <1450501415 dot 8390 dot 111 dot camel at oc7878010663>
On Fri, 18 Dec 2015, Steven Munroe wrote:
> > Well, I'd think the starting point is to implement operations following
> > the correct semantics, which are quite clear in both TR 24732:2009 and TS
> > 18661-2: as per IEEE 754-2008, conversions are correctly rounded with
> > correct exceptions.
> Then you should be specific! Specific examples with test cases.
All include testcases, tested with current git libdfp on POWER8
little-endian. Five of the six work correctly with the libgcc
conversions. All should be understood to be likely to apply to most of
the binary/decimal conversions in libdfp, in both directions, not just to
the conversions from _Decimal128 to double used to illustrate them,
because of the similarity of code used for different conversions. I think
together those issues provide reasonable coverage of the problems with
libdfp conversions that I've identified in this thread.
Joseph S. Myers