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From: sln on 8 Aug 2010 15:21 On Mon, 09 Aug 2010 00:23:42 +0700, michael20545 <a(a)a.com> wrote: >Hi all, > >I often need to convert 100s of SVG files to EPS format with Inkscape. >It is continuous process, so I decided to use Perl threads for >performing several jobs simultaneously. I'm new to Perl threads. Here is >my script. > > >use strict; >use threads; >use threads::shared; >use Cwd; >my $i : shared =0; >my $dir=getcwd(); >my @files=<*.svg>; >threads->new(\&convert_to_eps,1)->join(); >threads->new(\&convert_to_eps,2)->join(); >threads->new(\&convert_to_eps,3)->join(); > >sub convert_to_eps >{ > my $thread_num=$_[0]; > while($i<=$#files) > { > my $svg=$files[$i++]; > my $eps=$svg; > $eps=~ s/\.svg/.eps/; > print "$thread_num $svg\n"; > `inkscape -f "$dir\\$svg" -T -C -E "$dir\\$eps"`; > } >} > >Here works only first thread. What is wrong? > > In addition to the join() going to wait on the thread as was mentioned, I would think you need a lock around variable $i since it is shared and incremented amongst the three threads and it is not atomic for the assignment (increment maybe). Seems for Windows this lock is like a mutex. I tried an experiment without the lock and slept 1 second, hit pause/un-pause a few times, then started getting random duplicates. With the lock, it works fine. You can comment the lock for a test of with/without. -sln ---------------------- use strict; use threads; use threads::shared; use Cwd; # my $i : shared = 0; my $dir = getcwd(); my @files = <*>; my @threads; for (1 .. 3) { push @threads, threads->new( \&show_files, $_); } for (@threads) { $_->join(); } # sub show_files { my ($thread_num) = @_; while( $i <= $#files ) { my ($local_file, $local_i); { lock $i; $local_file = $files[$i++]; $local_i = $i; } print "$thread_num, $local_i, $dir/$local_file\n"; sleep(1); } }
From: sln on 8 Aug 2010 15:40 On Sun, 08 Aug 2010 12:21:20 -0700, sln(a)netherlands.com wrote: >On Mon, 09 Aug 2010 00:23:42 +0700, michael20545 <a(a)a.com> wrote: > >>Hi all, >> >>I often need to convert 100s of SVG files to EPS format with Inkscape. >>It is continuous process, so I decided to use Perl threads for >>performing several jobs simultaneously. I'm new to Perl threads. Here is >>my script. >> >> >>use strict; >>use threads; >>use threads::shared; >>use Cwd; >>my $i : shared =0; >>my $dir=getcwd(); >>my @files=<*.svg>; >>threads->new(\&convert_to_eps,1)->join(); >>threads->new(\&convert_to_eps,2)->join(); >>threads->new(\&convert_to_eps,3)->join(); >> >>sub convert_to_eps >>{ >> my $thread_num=$_[0]; >> while($i<=$#files) >> { >> my $svg=$files[$i++]; >> my $eps=$svg; >> $eps=~ s/\.svg/.eps/; >> print "$thread_num $svg\n"; >> `inkscape -f "$dir\\$svg" -T -C -E "$dir\\$eps"`; >> } >>} >> >>Here works only first thread. What is wrong? >> >> > >In addition to the join() going to wait on the thread as was >mentioned, I would think you need a lock around variable $i >since it is shared and incremented amongst the three threads >and it is not atomic for the assignment (increment maybe). >Seems for Windows this lock is like a mutex. > >I tried an experiment without the lock and slept 1 second, >hit pause/un-pause a few times, then started getting random >duplicates. With the lock, it works fine. You can comment the >lock for a test of with/without. > >-sln > >---------------------- >use strict; >use threads; >use threads::shared; >use Cwd; > ># > my $i : shared = 0; > my $dir = getcwd(); > my @files = <*>; > > my @threads; > for (1 .. 3) { > push @threads, threads->new( \&show_files, $_); > } > for (@threads) { > $_->join(); > } > The while condition has to be protected as well. Something like a while(1) condition then: # sub show_files { my ($thread_num) = @_; LOOP: while( 1 ) { my ($local_file, $local_i); { lock $i; last LOOP if $i > $#files; $local_file = $files[$i++]; $local_i = $i; } print "$thread_num, $local_i, $dir/$local_file\n"; # sleep(1); } } ># > sub show_files { > my ($thread_num) = @_; > while( $i <= $#files ) { > my ($local_file, $local_i); > { > lock $i; > $local_file = $files[$i++]; > $local_i = $i; > } > print "$thread_num, $local_i, $dir/$local_file\n"; > sleep(1); > } > }
From: sln on 8 Aug 2010 15:45 On Sun, 08 Aug 2010 12:40:09 -0700, sln(a)netherlands.com wrote: >The while condition has to be protected as well. >Something like a while(1) condition then: Or, better to just return: # sub show_files { my ($thread_num) = @_; while( 1 ) { my ($local_file, $local_i); { lock $i; return if $i > $#files; $local_file = $files[$i++]; $local_i = $i; } print "$thread_num, $local_i, $dir/$local_file\n"; } }
From: Wolf Behrenhoff on 9 Aug 2010 04:25 On 08.08.2010 21:40, sln(a)netherlands.com wrote: > The while condition has to be protected as well. > Something like a while(1) condition then: .... whatever else needs locking. It is easy to forget some locking somewhere. So my suggestion is to use Thread::Queue; then enqueue all svg filenames in a queue. Now create threads which convert files while dequeue_nb retuns a filename. Wolf
From: sln on 9 Aug 2010 07:41
On Mon, 09 Aug 2010 10:25:29 +0200, Wolf Behrenhoff <NoSpamPleaseButThisIsValid3(a)gmx.net> wrote: >On 08.08.2010 21:40, sln(a)netherlands.com wrote: >> The while condition has to be protected as well. >> Something like a while(1) condition then: > >... whatever else needs locking. It is easy to forget some locking >somewhere. > >So my suggestion is to >use Thread::Queue; > >then enqueue all svg filenames in a queue. Now create threads which >convert files while dequeue_nb retuns a filename. > >Wolf Of course, but the OP is taking small steps first. -sln |