Re: Threads and Progress Monitors

[Michael Lazzaro]

On Thursday, May 29, 2003, at 12:45 PM, Dave Whipp wrote:
"Michael Lazzaro" <[EMAIL PROTECTED]> wrote in>     # But if 
you want
to get the thread object, so you can monitor it's
    {
        ...
        my $tid = thread &slow_func_impl(...);
        while $tid.active {
            status_monitor($tid.progress);
            sleep 60;
        }
        return $tid.result;
    }
To my eye, that looks pretty darn slick.
You might be a bit frustrated if the &slow_func_impl took 61 seconds 
:-(.
How do we interrupt the C<sleep>? Possibly in the same way as we'd 
timeout a
blocking IO operations.
Personally, I'd be happy with just making the C<sleep> a smaller 
number, like one second, or a fifth of a second, or whatever.  You want 
the status_monitor to be updated no more often than it needs to be, but 
often enough that it's not lagging.

But if you really wanted wake-immediately-upon-end, I'd add that as a 
variant of C<sleep>.  For example, you might want a variant that 
blocked until a given variable "changed", just like in debuggers; that 
would allow:

    {
        my $tid = thread &slow_func_impl(...);
        while $tid.active {
            status_monitor($tid.progress);
            sleep( 60, watch => \($tid.progress) );     # do you even 
need the '\'?
        }
        return $tid.result;
    }

... which would sleep 60 seconds, or until the .progress attribute 
changed, whichever came first.

You could make more builtins for that, but I think I'd like them to 
just be C<sleep> or C<wait> variants.  Obvious possibilities:

    sleep 60;                 # sleep 60 seconds
    sleep( block => $tid );   # sleep until given thread is complete
    sleep( watch => \$var );  # sleep until given var changes value
    sleep( 60, block => $tid, watch => [\$var1, \$var2, \$var3] );  
five tests

    $tid.sleep(...);    # sleep the given thread, instead of this one

MikeL