Revert back to calling CORE::rand

1. Revert back to calling CORE::rand() to set the internal seed. MCE and MCE::Child cannot assume the srand or setter function used by the application for predictability. 2. Add class methods MCE->seed and MCE::Child->seed to retrieve the seed.
marioroy · Jun 10, 2024 · 318306e · 318306e
1 parent 5d561ca
commit 318306e
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Showing 4 changed files with 36 additions and 48 deletions.
diff --git a/lib/MCE.pm b/lib/MCE.pm
@@ -121,7 +121,7 @@ BEGIN {
          return $self->{$_p};
       };
    }
-   for my $_p (qw( chunk_id task_id task_wid wid )) {
+   for my $_p (qw( chunk_id seed task_id task_wid wid )) {
       *{ $_p } = sub () {
          my $self = shift; $self = $MCE unless ref($self);
          return $self->{"_${_p}"};
@@ -641,25 +641,7 @@ sub spawn {
          for (0 .. $_max_workers - 1);
    }
 
-   # The PDL module 2.062 ~ 2.089 exports its own srand() function, that
-   # silently clobbers Perl's srand function, and does not seed Perl's
-   # pseudo-random generator. https://perlmonks.org/?node_id=11159773
-
-   if ( $INC{'PDL/Primitive.pm'} ) {
-      # Call PDL's random() function if exported i.e. use PDL.
-
-      my $caller = caller(); local $@;
-      $caller = caller(1) if ( $caller =~ /^MCE/ );
-      $caller = caller(2) if ( $caller =~ /^MCE/ );
-      $caller = caller(3) if ( $caller =~ /^MCE/ );
-
-      $self->{_seed} = eval "$caller->can('random')"
-         ? int(PDL::Primitive::random() * 1e9)
-         : int(CORE::rand() * 1e9);
-   }
-   else {
-      $self->{_seed} = int(CORE::rand() * 1e9);
-   }
+   $self->{_seed} = int(CORE::rand() * 1e9);
 
    ## -------------------------------------------------------------------------
 
@@ -1609,8 +1591,7 @@ sub sess_dir {
    return $self->{_sess_dir} if defined $self->{_sess_dir};
 
    if ($self->{_wid} == 0) {
-      $self->{_sess_dir} = $self->{_spawned}
-         ? _make_sessdir($self) : undef;
+      $self->{_sess_dir} = $self->{_spawned} ? _make_sessdir($self) : undef;
    }
    else {
       my $_chn        = $self->{_chn};
@@ -2033,17 +2014,15 @@ sub _dispatch {
       MCE::Hobo->_clear() if $INC{'MCE/Hobo.pm'};
    }
 
-   # Sets the seed of the base generator uniquely between workers.
+   # Set the seed of the base generator uniquely between workers.
    # The new seed is computed using the current seed and ID value.
    # One may set the seed at the application level for predictable
    # results (non-thread workers only). Ditto for Math::Prime::Util,
    # Math::Random, Math::Random::MT::Auto, and PDL.
    #
-   # MCE 1.892, 2024-06-08
-   #     Removed check if spawning threads i.e. use_threads.
-   #     Predictable output matches non-threads for CORE,
-   #     Math::Prime::Util, and Math::Random::MT::Auto.
-   #     https://perlmonks.org/?node_id=11159834
+   # MCE 1.892, 2024-06-08: Enable predictability running threads.
+   # Output matches non-threads for CORE, Math::Prime::Util, and
+   # Math::Random::MT::Auto. https://perlmonks.org/?node_id=11159834
 
    {
       my $_wid  = $_args[1];

diff --git a/lib/MCE/Child.pm b/lib/MCE/Child.pm
@@ -111,25 +111,7 @@ sub init {
       $_DATA->{ $pkg } = MCE::Child::_hash->new( $chnl );
       $_DATA->{"$pkg:id"} = 0;
 
-      # The PDL module 2.062 ~ 2.089 exports its own srand() function, that
-      # silently clobbers Perl's srand function, and does not seed Perl's
-      # pseudo-random generator. https://perlmonks.org/?node_id=11159773
-
-      if ( $INC{'PDL/Primitive.pm'} ) {
-         # Call PDL's random() function if exported i.e. use PDL.
-
-         my $caller = caller(); local $@;
-         $caller = caller(1) if ( $caller =~ /^MCE/ );
-         $caller = caller(2) if ( $caller =~ /^MCE/ );
-         $caller = caller(3) if ( $caller =~ /^MCE/ );
-
-         $_DATA->{"$pkg:seed"} = eval "$caller->can('random')"
-            ? int(PDL::Primitive::random() * 1e9)
-            : int(CORE::rand() * 1e9);
-      }
-      else {
-         $_DATA->{"$pkg:seed"} = int(CORE::rand() * 1e9);
-      }
+      $_DATA->{"$pkg:seed"} = int(CORE::rand() * 1e9);
 
       $MCE::_GMUTEX->unlock() if ( $_tid && $MCE::_GMUTEX );
    }
@@ -264,7 +246,7 @@ sub create {
          MCE::Child->_clear() if $INC{'MCE/Child.pm'};
          MCE::Hobo->_clear() if $INC{'MCE/Hobo.pm'};
 
-         # Sets the seed of the base generator uniquely between workers.
+         # Set the seed of the base generator uniquely between workers.
          # The new seed is computed using the current seed and ID value.
          # One may set the seed at the application level for predictable
          # results. Ditto for PDL, Math::Prime::Util, Math::Random, and
@@ -559,6 +541,13 @@ sub result {
    wantarray ? @{ delete $self->{RESULT} } : delete( $self->{RESULT} )->[-1];
 }
 
+sub seed {
+   _croak('Usage: MCE::Child->seed()') if ref($_[0]);
+   my $pkg = exists $_SELF->{PKG} ? $_SELF->{PKG} : "$$.$_tid.".caller();
+
+   return $_DATA->{"$pkg:seed"};
+}
+
 sub self {
    ref($_[0]) ? $_[0] : $_SELF;
 }
@@ -1543,6 +1532,13 @@ C<wantarray> aware.
  my @res2 = $child2->result();  # ( foo )
  my $res2 = $child2->result();  #   foo
 
+=item MCE::Child->seed()
+
+Class method that returns the internal random generated seed or undefined.
+The seed is generated once during init or initial create.
+
+Current API available since 1.895.
+
 =item MCE::Child->self()
 
 Class method that allows a child to obtain it's own I<MCE::Child> object.

diff --git a/lib/MCE/Core.pod b/lib/MCE/Core.pod
@@ -1474,6 +1474,15 @@ Sending to C<IO::All> { File, Pipe, STDIO } is supported since MCE 1.845.
  MCE->say($out, "sent to stdout");
  MCE->say($err, "sent to stderr");
 
+=head2 MCE->seed ( void )
+
+=head2 $mce->seed ( void )
+
+Returns the internal random generated seed or undefined.
+The seed is generated each time, prior to spawning a MCE session.
+
+Current API available since 1.895.
+
 =head2 MCE->sess_dir ( void )
 
 =head2 $mce->sess_dir ( void )

diff --git a/lib/MCE/Subs.pm b/lib/MCE/Subs.pm
@@ -102,6 +102,7 @@ sub mce_chunk_size  ( ) { return $MCE::MCE->chunk_size(); }
 sub mce_max_retries ( ) { return $MCE::MCE->max_retries(); }
 sub mce_max_workers ( ) { return $MCE::MCE->max_workers(); }
 sub mce_pid         ( ) { return $MCE::MCE->pid(); }
+sub mce_seed        ( ) { return $MCE::MCE->seed(); }
 sub mce_sess_dir    ( ) { return $MCE::MCE->sess_dir(); }
 sub mce_task_id     ( ) { return $MCE::MCE->task_id(); }
 sub mce_task_name   ( ) { return $MCE::MCE->task_name(); }
@@ -176,6 +177,7 @@ sub _export_subs {
       *{ $_package . '::mce_max_retries' } = \&mce_max_retries;
       *{ $_package . '::mce_max_workers' } = \&mce_max_workers;
       *{ $_package . '::mce_pid'         } = \&mce_pid;
+      *{ $_package . '::mce_seed'        } = \&mce_seed;
       *{ $_package . '::mce_sess_dir'    } = \&mce_sess_dir;
       *{ $_package . '::mce_task_id'     } = \&mce_task_id;
       *{ $_package . '::mce_task_name'   } = \&mce_task_name;
@@ -371,6 +373,8 @@ MCE methods are described in L<MCE::Core>.
 
 =item * mce_pid
 
+=item * mce_seed
+
 =item * mce_sess_dir
 
 =item * mce_task_id