From doomvox at gmail.com  Sat Jul  4 12:20:19 2020
From: doomvox at gmail.com (Joseph Brenner)
Date: Sat, 4 Jul 2020 12:20:19 -0700
Subject: [sf-perl] the next Raku study group is on the 12th
Message-ID: <CAFfgvXVhHVWSWW2V7mi7iCNYyEc9MF+E_Xf-TGLX2eWP=FnLQA@mail.gmail.com>

After taking a break for the weekend of the 4th, we'll be back with
the Raku study group that time forgot.  Sunday at 2pm, via zoom.

With a free account, zoom technically limits meeting length to 40mins,
so I'm scheduling three meetings at the top of the hour for 2pm, 3pm,
4pm. If they're enforcing the limit, we'll take 20 minute breaks from
the video and then resume (if they're not enforcing it, we'll just
stay in the first meeting).

RSVP if you like:
https://www.meetup.com/San-Francisco-Perl/events/271718963/

2pm:
https://us04web.zoom.us/j/73585912227?pwd=ZHRzUWk3R3lWRER5NUZpZSsvN1BPZz09

3pm:
https://us04web.zoom.us/j/79384981433?pwd=bXZ1U1FEK0lNSHlyRmFab1RIc0poQT09

4pm:
https://us04web.zoom.us/j/77506196681?pwd=TVZpSkVnUFMxNUVRTDhBRlJWRkx1UT09

From dpchrist at holgerdanske.com  Wed Jul  8 16:38:50 2020
From: dpchrist at holgerdanske.com (David Christensen)
Date: Wed, 8 Jul 2020 16:38:50 -0700
Subject: [sf-perl] threads, threads::shared, and multiple locked variables
Message-ID: <5a1f2478-0bbc-73f0-f019-575c9279a403@holgerdanske.com>

sanfrancisco-pm:

I have been experimenting with concurrent programming with Perl, 
threads, and threads::shared.  I have successfully used a shared 
variable, lock(), cond_wait(), and cond_broadcast() to ensure 
thread-safe access to one shared resource.


I would now like to ensure thread-safe access to multiple shared 
resources.  Specifically, if a thread desires access to any one of 
several shared resources, how can it block, wake up when one resource is 
available (and locked), and determine which resource to access?


David

From not.com at gmail.com  Thu Jul  9 14:40:45 2020
From: not.com at gmail.com (yary)
Date: Thu, 9 Jul 2020 17:40:45 -0400
Subject: [sf-perl] threads, threads::shared,
 and multiple locked variables
In-Reply-To: <5a1f2478-0bbc-73f0-f019-575c9279a403@holgerdanske.com>
References: <5a1f2478-0bbc-73f0-f019-575c9279a403@holgerdanske.com>
Message-ID: <CAG2CFAao2akKFnGH1DZeui_kVN__wEyKz8L1QGpfWtbuHp+Qtg@mail.gmail.com>

How about code with # what goes here? comments

I'm a little fuzzy on what the question is. It sounds a little like
the old-school "select" call that takes a bit vector representing file
handles, which paused and then filled 3 other bit vectors saying which
handles were ready to read, write, or had an exception-is that what
the question is-using "threads" mechanisms to signal which of several
things are ready?

perldoc -f select shows what I remember as similar:
my ($nfound, $timeleft) =
    select(my $rout = $rin, my $wout = $win, my $eout = $ein, $timeout);

...my go-to in these situations is to `use MCE;` and figure out which
of its many idioms applies...
-y

On Wed, Jul 8, 2020 at 7:45 PM David Christensen
<dpchrist at holgerdanske.com> wrote:
>
> sanfrancisco-pm:
>
> I have been experimenting with concurrent programming with Perl,
> threads, and threads::shared.  I have successfully used a shared
> variable, lock(), cond_wait(), and cond_broadcast() to ensure
> thread-safe access to one shared resource.
>
>
> I would now like to ensure thread-safe access to multiple shared
> resources.  Specifically, if a thread desires access to any one of
> several shared resources, how can it block, wake up when one resource is
> available (and locked), and determine which resource to access?
>
>
> David
> _______________________________________________
> SanFrancisco-pm mailing list
> SanFrancisco-pm at pm.org
> https://mail.pm.org/mailman/listinfo/sanfrancisco-pm

From dpchrist at holgerdanske.com  Thu Jul  9 17:08:18 2020
From: dpchrist at holgerdanske.com (David Christensen)
Date: Thu, 9 Jul 2020 17:08:18 -0700
Subject: [sf-perl] threads, threads::shared,
 and multiple locked variables
In-Reply-To: <CAG2CFAao2akKFnGH1DZeui_kVN__wEyKz8L1QGpfWtbuHp+Qtg@mail.gmail.com>
References: <5a1f2478-0bbc-73f0-f019-575c9279a403@holgerdanske.com>
 <CAG2CFAao2akKFnGH1DZeui_kVN__wEyKz8L1QGpfWtbuHp+Qtg@mail.gmail.com>
Message-ID: <8634a35e-99fa-f4f5-9b7e-d2a23c71fc57@holgerdanske.com>

On 2020-07-09 14:40, yary wrote:

> On Wed, Jul 8, 2020 at 7:45 PM David Christensen wrote:

>> I have been experimenting with concurrent programming with Perl, 
>> threads, and threads::shared.  I have successfully used a shared 
>> variable, lock(), cond_wait(), and cond_broadcast() to ensure 
>> thread-safe access to one shared resource.
>> 
>> 
>> I would now like to ensure thread-safe access to multiple shared 
>> resources.  Specifically, if a thread desires access to any one of 
>> several shared resources, how can it block, wake up when one
>> resource is available (and locked), and determine which resource to
>> access?

> How about code with # what goes here? comments
> 
> I'm a little fuzzy on what the question is. It sounds a little like 
> the old-school "select" call that takes a bit vector representing
> file handles, which paused and then filled 3 other bit vectors saying
> which handles were ready to read, write, or had an exception-is that
> what the question is-using "threads" mechanisms to signal which of
> several things are ready?
> 
> perldoc -f select shows what I remember as similar: my ($nfound,
> $timeleft) = select(my $rout = $rin, my $wout = $win, my $eout =
> $ein, $timeout);


Yes, that's the idea -- except that I am working with shared variables 
[1], rather than file handles.


> ...my go-to in these situations is to `use MCE;` and figure out
> which of its many idioms applies...


MCE [2] appears to provide a framework for creating multiple identical 
workers and partitioning work among them (?).


My question is more related to first principles of concurrent programming.


I am attempting to create a general-purpose Perl library for flow-based 
programming (FBP) [3], whereby multiple independent "processes" send 
data "items" to each other via communication "connections" and work 
together as a overall program.


FBP's are easily represented by directed graphs -- "processes" are nodes 
(boxes) and "connections" are edges (arrows).  For example, here is a 
FBP to read a file (src), compress the contents, tee the compressed 
stream into two streams, write the first duplicate stream to a file 
(dst.gz), checksum the second duplicate stream, and write the checksum 
to a file (dst.gz,md5):


                        +-----+ -> write(dst.gz)
read(src)-> compress-> | tee |
                        +-----+ -> checksum -> write(dst.gz.md5)


I use 'threads' to create and manage one thread for each process and I 
use 'threads::shared' to create and manage one array for each 
connection.  These modules work for simple programs like the above with 
processes that have single inputs and single or multiple outputs, but, 
in general, FBP's will include processes with multiple inputs:

... proc1 -> +------+
              | func | ...
... proc2 -> +------+


So, I need a mechanism for a thread to go to sleep on multiple shared 
variables, wake up when one of those variables signals, and then know 
which variable woke it up.


I am starting to believe that my question is really a feature request 
for threads::shared (and/or Perl?).


I am open to alternative approaches, but the goal is a general-purpose 
FBP library.


(As a work-around, I am implementing a polling solution with a 
configurable sleep delay.)


(Perhaps I could build a work-around using file handles and 'select', 
but file handles are scarce resources and a large FBP could consume many.)


David


[1] https://perldoc.perl.org/threads/shared.html

[2] https://metacpan.org/pod/distribution/MCE/lib/MCE.pod

[3] https://en.wikipedia.org/wiki/Flow-based_programming

From doomvox at gmail.com  Fri Jul 17 16:24:50 2020
From: doomvox at gmail.com (Joseph Brenner)
Date: Fri, 17 Jul 2020 16:24:50 -0700
Subject: [sf-perl] Suddenly, the Raku Study Group
Message-ID: <CAFfgvXWp6QaTNU0rAUF3jHjp2Ne2TA+bP7CL5=OCLeKGoAHN3w@mail.gmail.com>

No one expects the online Raku study group.
Sunday at 2pm, via zoom.

RSVP to:
https://www.meetup.com/San-Francisco-Perl/events/271993517/

With a free account, zoom technically limits meeting length to 40mins,
so I'm scheduling three meetings at the top of the hour for 2pm, 3pm,
4pm. If they're enforcing the limit, we'll take 20 minute breaks from
the video and then resume (if they're not enforcing it, we'll just
stay in the first meeting).

2pm:
https://us04web.zoom.us/j/76633459313?pwd=eW50SDhUNXUxVzE5alRKTUFXUHZoUT09

3pm:
https://us04web.zoom.us/j/75234854364?pwd=S2hPMk5sYjVSZ3RjZ1JMS3dQajdFQT09

4pm:
https://us04web.zoom.us/j/71339073769?pwd=MWZTTEVUMmx5N2lpYTZQQlpDd2V0QT09

From doomvox at gmail.com  Fri Jul 24 10:30:27 2020
From: doomvox at gmail.com (Joseph Brenner)
Date: Fri, 24 Jul 2020 10:30:27 -0700
Subject: [sf-perl] Raku Study group, Sunday July26th, 2pm
Message-ID: <CAFfgvXXJnRXHQ3snnUCwMeXhsGNhbOWDDb7_NYcu+5jFRAdruA@mail.gmail.com>

What song did the sirens sing, and when will the next Raku study group be?

Sunday at 2pm, via zoom.

https://us04web.zoom.us/j/77192674311?pwd=VzQrNUQ4RU4xZG9qWm9EUlBsQllOdz09

Password:  4RakuRoll

From doomvox at gmail.com  Thu Jul 30 13:44:47 2020
From: doomvox at gmail.com (Joseph Brenner)
Date: Thu, 30 Jul 2020 13:44:47 -0700
Subject: [sf-perl] Raku study group, Sunday Aug 2nd, 2pm
Message-ID: <CAFfgvXWjzZ-7jM=kQbAcbTJh4Rt6JD=SQq4XwgsAr7FUR2ZOGg@mail.gmail.com>

It's alive!  The Raku study group :

Sunday, August 2nd, at 2pm, via zoom.

https://us04web.zoom.us/j/73188828798?pwd=MWdIbVo3U1hpQStvZUo3YjRicGtrZz0909

Password: 4RakuRoll

RSVP:

https://www.meetup.com/San-Francisco-Perl/events/272258217/