Threads and print

sandy1028 has asked for the wisdom of the Perl Monks concerning the following question:

Hi, Here in the for loop, the values passed is between 1 to 200000.
In the log file only 600 values are printed. How can I print all the values in the log file by creating 5 threads.

#! perl -slw
use strict;
use threads;
use threads::shared;

our $N ||= 100;

our $from=1;
our $to=200000;

sub worker {
    my $tid = threads->tid;
    my( $log, $semRef, $from, $to ) = @_;
    for my $file ( $from .. $to ) {
        ## Simulate doing some processing
        ## Lock the log file semaphore before writing
        lock $$semRef;
        ## And write to the log
        printf $log "[%2d] Processesing file%3d\n",
            $tid, $file;
        ## The lock is released automatically at the end of the block
    }
}

## A shared variable used as a semaphore for the log file resource
my $logSem :shared;
## Open the log file in the main thread
open my $log, '>', 'myLog2' or die $!;
my @threads = map{
    ## create the workers passing the log file handle and semaphore
    threads->create( \&worker, $log, \$logSem,$_*$N, $_*$N + $N -1);
} 0 .. 5; ## 5 threads each processing 100 "files"
## Wait till they are done
$_->join for @threads;

## close the log
close $log;
[download]

Comment on Threads and print Download Code

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Re: Threads and print by cdarke (Prior) on Apr 16, 2009 at 08:24 UTC
By correcting your calculation of $N. `$N = $to/5;` [download] However, you still have an issue because the records overlap. Didn't we discuss this before here 755631? I suggest you use a single thread to write to the log file, rather than trying to get all the threads to write at the same time.	[reply] [d/l]
Re^2: Threads and print by sandy1028 (Sexton) on Apr 16, 2009 at 08:39 UTC
Can you please tell me some tutorial regarding it. Like how to create a single log file for each thread. It the $to value is increased also only 5 threads should be created.	[reply]
Re^3: Threads and print by sandy1028 (Sexton) on Apr 16, 2009 at 08:45 UTC
The above code works fine with commenting lock $$semRef; Can anyone please explain me what is the use of locking method in the above code.	[reply]
Re: Threads and print by gone2015 (Deacon) on Apr 16, 2009 at 08:53 UTC
`my @threads = map { ## create the workers passing the log file handle and semaphore threads->create( \&worker, $log, \$logSem,$_$N, $_$N + $N -1); } 0 .. 5; ## 5 threads each processing 100 "files"` [download] ...<hem>that's 6 threads, shirly ? To process `$from..$to` in `$t` threads, how about: `my @threads = map{ threads->create( \&worker, $log, \$logSem, $from + ($_ - 1), $t, $to +) ; } 1 .. $t ;` [download] and in the thread: `my( $log, $semRef, $from, $step, $to ) = @_; for (my $file = $from ; $file <= $to ; $file += $step) { ...... } ;` [download] which deals with the number of files not being an exact multiple of the number of threads, and copes with `$from..$to` range where `$from` is not zero and `$to` is included in the range...	[reply] [d/l] [select]
Re^2: Threads and print by sandy1028 (Sexton) on Apr 16, 2009 at 09:52 UTC
Can you please tell me how to create single log file per thread and the values are in sequence order.	[reply]
Re^3: Threads and print by cdarke (Prior) on Apr 16, 2009 at 11:40 UTC
'ang about gov'ner, I thought you wanted to have all the threads writing to the same log file? No? OK, then open a new log file in the worker function. Use some unique value passed as a parameter as part of the file name.	[reply]
Re^4: Threads and print by sandy1028 (Sexton) on Apr 17, 2009 at 04:57 UTC
Re^4: Threads and print by sandy1028 (Sexton) on Apr 20, 2009 at 06:06 UTC


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