From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=unavailable autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!mx02.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail From: "Dmitry A. Kazakov" Newsgroups: comp.lang.ada Subject: Re: RFC: Prototype for a user threading library in Ada Date: Sun, 26 Jun 2016 08:15:30 +0200 Organization: Aioe.org NNTP Server Message-ID: References: <58b78af5-28d8-4029-8804-598b2b63013c@googlegroups.com> NNTP-Posting-Host: w/2xSGckQeJEFvqsQFNodA.user.gioia.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 X-Notice: Filtered by postfilter v. 0.8.2 Xref: news.eternal-september.org comp.lang.ada:30940 Date: 2016-06-26T08:15:30+02:00 List-Id: On 2016-06-26 05:21, Randy Brukardt wrote: > "Dmitry A. Kazakov" wrote in message > news:nkl8bm$19q7$1@gioia.aioe.org... >> On 2016-06-24 02:38, rieachus@comcast.net wrote: >>> I don't get it. If this is your "motivation": >>> >>>> The motivation is a two-liner. Let you have some consumer of data: >>>> >>>> procedure Write (Buffer : String; Last : out Integer); >>>> >>>> It may take less than the whole string when called, but will take more >>>> data later. So, the parameter Last. Now you want to write a program in a >>>> *normal* way: >>>> >>>> Write ("This"); >>>> Write ("That"); >>>> >>>> That's it. >>> >>> You may want to make your Last parameter in or in out, but that's a >>> detail. >> >> It is not a detail. The caller of Write does not know how much data the >> transport layer is ready to accept. That is the nature of non-blocking >> I/O. Write takes as much data it can and tells through Last where the >> caller must continue *later*. >> >> A blocking busy-waiting wrapper looks this way: >> >> procedure Write (Buffer : String) is >> First : Integer := Buffer'First; >> Last : Integer; >> begin >> loop >> Write (Buffer (First..Buffer'Last), Last); >> exit when Last = Buffer'Last; >> First := Last + 1; >> end loop; >> end Write; > > You forgot the "delay 0.0;" I didn't. With yielding processor it would no more be busy-waiting. > That, combined with proper tasking runtimes, would seem to provide better > results than doing all one thing (task = thread) or all othe ther (some > fancy coroutine system). Not really. The whole point is that in the imaginary case under consideration you don't need a timer event in order to wake Write up. I presume that there is an I/O event that tells this: procedure Write (Buffer : String) is First : Integer := Buffer'First; Last : Integer; begin loop Write (Buffer (First..Buffer'Last), Last); exit when Last = Buffer'Last; First := Last + 1; Output_Buffer.Wait_For_State (Not_Full); -- A PO's entry call end loop; end Write; Now the code is exactly same for a task and a co-routine. What is left is the overhead of thread scheduling to remove. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de