From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.3 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 16031 invoked from network); 29 Jun 2020 20:17:35 -0000 Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with ESMTPUTF8; 29 Jun 2020 20:17:35 -0000 Received: (qmail 4073 invoked by uid 550); 29 Jun 2020 20:17:33 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 4055 invoked from network); 29 Jun 2020 20:17:32 -0000 Date: Mon, 29 Jun 2020 16:17:19 -0400 From: Rich Felker To: musl@lists.openwall.com Message-ID: <20200629201719.GC6430@brightrain.aerifal.cx> References: <32b4-5ef9e500-33-6d961680@199533904> <20200629162642.GI2048759@port70.net> <20200629181540.GC13001@voyager> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200629181540.GC13001@voyager> User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] Posits support under Musl libc? On Mon, Jun 29, 2020 at 08:15:40PM +0200, Markus Wichmann wrote: > On Mon, Jun 29, 2020 at 06:26:42PM +0200, Szabolcs Nagy wrote: > > i would not hold my breath for posit support even if it was the > > best possible floating-point format. > > > > it has to be properly standardized and added to hw architectures. > > > > then the related software standards need to be developed (abi, > > programming language support, math library behaviour for special > > cases, printf format specifiers, etc) > > > > then the tooling support has to be added (compilers, emulators, > > softfloat libraries, etc) > > > > then we can come back and consider doing something about it in > > musl. > > > > (and even then it will take time for it to be usable in user > > code: requires widely deployed hw, protocol and file format > > updates, new algorithm designs and review of existing algorithms > > for compatibility) > > In addition, Posit support is going to run into the problem that IEEE > 754 implementations are readily available /right now/ and are "good > enough" for most applications. Hell, most applications don't even > require floating-point at all. The good can sometimes be the enemy of > the perfect, but here I am squarely on the side of pragmatism. Not only are they "good enough"; pretty much everyone except the inventor of posits and a small fan club thinks IEEE 754 floating point is *better* than posits. In any case, musl is not a platform for launching and promoting new experimental ideas. We implement interfaces where there is already widespread consensus that they belong in libc, either as a result of a published standard or agreement between multiple libc implementations across different systems(*). The Austin Group (responsible for POSIX) generally doesn't accept new ideas without a sponsor (an existing implementation already committed to it) and agreement from members. WG14 (C standard) sometimes takes new ideas but they usually turn out botched when it happens; ideally they go through optional TRs first and only become standard if they're widely liked. Rich (*) That's not entirely true. We also have thin syscall wrappers for Linux-specific functionality, on the presumption that it's not any big design or bloat commitment, but sometimes this turns out to be false, e.g. in the case of sendmmsg/recvmmsg.