Date: Mon, 29 Jun 2020 16:17:19 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: 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.
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