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Hermes SMTP Server) with ESMTPA ID 532cfd7d3e45bfdabbdcd4ecca2a40d7; Thu, 10 Apr 2025 00:08:25 +0000 (UTC) Message-ID: <1f5c1e4d911d8e99b8343148a84a4a0cdfdd5bd1.camel@sbcglobal.net> Subject: Comment on 23-174 From: Van Snyder To: sc22wg5 Date: Wed, 09 Apr 2025 17:08:24 -0700 Content-Type: multipart/alternative; boundary="=-LUV+dnjCpp94DJBXTZr/" User-Agent: Evolution 3.46.4-2 MIME-Version: 1.0 References: <1f5c1e4d911d8e99b8343148a84a4a0cdfdd5bd1.camel.ref@sbcglobal.net> X-Mailer: WebService/1.1.23665 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.yahoo Sender: owner-sc22wg5@open-std.org Precedence: bulk --=-LUV+dnjCpp94DJBXTZr/ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Asynchronous blocks were proposed in Section 18 in 97-114. As described by Burns and Wellings in "Concurrent and Real-Time Programming in Ada," processor developers and their clients discovered that Ada tasks have significant inherent overhead imposed by their design specification. "Protected Variables" were added to overcome this. They are essentially coroutines. Coroutines (and iterators) have been proposed for Fortran, and were for a short time on the development program. Their utility in concurrent programming is well known. They should be put back onto the development program as part of the 23-174 work item. See 04-380r2, 23-107 (a TR proposal), and 24-118. If Fortran tasks are permitted to invoke any procedure, not just pure ones, and allowed concurrent writes, it would be useful to have an exclusive-use mechanism. Many languages have critical sections or monitor procedures or both (and some rely on the lower level concept of semaphores). Fortran has a CRITICAL section, but it applies only to coarrays. That should be extended to asynchronous tasks. And monitor procedures would be useful too, in both contexts. A PARALLEL construct that specifies concurrently-executable blocks was proposed in 06-187. Bill Long pointed out that this could be faked using DO CONCURRENT with SELECT CASE inside. But an explicit syntactic principle that did it would be easier to write and understand, and maybe would give more clues to optimizers. --=-LUV+dnjCpp94DJBXTZr/ Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
Asynchronous blocks were proposed in Section = 18 in 97-114.

As described by Burns and Wellings i= n "Concurrent and Real-Time Programming in Ada," processor developers and t= heir clients discovered that Ada tasks have significant inherent overhead i= mposed by their design specification. "Protected Variables" were added to o= vercome this. They are essentially coroutines. Coroutines (and iterators) h= ave been proposed for Fortran, and were for a short time on the development= program. Their utility in concurrent programming is well known. They shoul= d be put back onto the development program as part of the 23-174 work item.= See 04-380r2, 23-107 (a TR proposal), and 24-118.

If Fortran tasks are permitted to invoke any procedure, not just pure ones= , and allowed concurrent writes, it would be useful to have an exclusive-us= e mechanism. Many languages have critical sections or monitor procedures or= both (and some rely on the lower level concept of semaphores). Fortran has= a CRITICAL section, but it applies only to coarrays. That should be extend= ed to asynchronous tasks. And monitor procedures would be useful too, in bo= th contexts.

A PARALLEL construct that specifies c= oncurrently-executable blocks was proposed in 06-187. Bill Long pointed out= that this could be faked using DO CONCURRENT with SELECT CASE inside. But = an explicit syntactic principle that did it would be easier to write and un= derstand, and maybe would give more clues to optimizers.

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