File Coverage

blib/lib/MCE/Stream.pm

Criterion	Covered	Total	%
statement	280	368	76.0
branch	126	244	51.6
condition	52	103	50.4
subroutine	19	23	82.6
pod	5	5	100.0
total	482	743	64.8

###############################################################################
## ----------------------------------------------------------------------------
## Parallel stream model for chaining multiple maps and greps.
##
###############################################################################

package MCE::Stream;

use strict;
use warnings;

no warnings qw( threads recursion uninitialized );

our $VERSION = '1.902';

## no critic (BuiltinFunctions::ProhibitStringyEval)
## no critic (Subroutines::ProhibitSubroutinePrototypes)
## no critic (TestingAndDebugging::ProhibitNoStrict)

use Scalar::Util qw( looks_like_number );

use MCE;
use MCE::Queue;

our @CARP_NOT = qw( MCE );

my $_tid = $INC{'threads.pm'} ? threads->tid() : 0;

sub CLONE {
   $_tid = threads->tid() if $INC{'threads.pm'};
}

###############################################################################
## ----------------------------------------------------------------------------
## Import routine.
##
###############################################################################

my ($_MCE, $_def, $_params, $_tag) = ({}, {}, {}, 'MCE::Stream');
my ($_prev_c, $_prev_m, $_prev_n, $_prev_w) = ({}, {}, {}, {});
my ($_user_tasks, $_queue) = ({}, {});

sub import {
   my ($_class, $_pkg) = (shift, caller);

   my $_p = $_def->{$_pkg} = {
      MAX_WORKERS  => 'auto',
      CHUNK_SIZE   => 'auto',
      DEFAULT_MODE => 'map',
   };

   ## Import functions.
   if ($_pkg !~ /^MCE::/) {
      no strict 'refs'; no warnings 'redefine';
      *{ $_pkg.'::mce_stream_f' } = \&run_file;
      *{ $_pkg.'::mce_stream_s' } = \&run_seq;
      *{ $_pkg.'::mce_stream'   } = \&run;
   }

   ## Process module arguments.
   while ( my $_argument = shift ) {
      my $_arg = lc $_argument;

      $_p->{MAX_WORKERS}  = shift, next if ( $_arg eq 'max_workers' );
      $_p->{CHUNK_SIZE}   = shift, next if ( $_arg eq 'chunk_size' );
      $_p->{TMP_DIR}      = shift, next if ( $_arg eq 'tmp_dir' );
      $_p->{FREEZE}       = shift, next if ( $_arg eq 'freeze' );
      $_p->{THAW}         = shift, next if ( $_arg eq 'thaw' );
      $_p->{INIT_RELAY}   = shift, next if ( $_arg eq 'init_relay' );
      $_p->{USE_THREADS}  = shift, next if ( $_arg eq 'use_threads' );
      $_p->{DEFAULT_MODE} = shift, next if ( $_arg eq 'default_mode' );

                            shift, next if ( $_arg eq 'fast' ); # ignored

      ## Sereal 3.015+, if available, is used automatically by MCE 1.8+.
      if ( $_arg eq 'sereal' ) {
         if ( shift eq '0' ) {
            require Storable;
            $_p->{FREEZE} = \&Storable::freeze;
            $_p->{THAW}   = \&Storable::thaw;
         }
         next;
      }

      _croak("Error: ($_argument) invalid module option");
   }

   _croak("Error: (DEFAULT_MODE) is not valid")
      if ($_p->{DEFAULT_MODE} ne 'grep' && $_p->{DEFAULT_MODE} ne 'map');

   $_p->{MAX_WORKERS} = MCE::_parse_max_workers($_p->{MAX_WORKERS});

   MCE::_validate_number($_p->{MAX_WORKERS}, 'MAX_WORKERS', $_tag);
   MCE::_validate_number($_p->{CHUNK_SIZE}, 'CHUNK_SIZE', $_tag)
      unless ($_p->{CHUNK_SIZE} eq 'auto');

   return;
}

###############################################################################
## ----------------------------------------------------------------------------
## Gather callback to ensure chunk order is preserved during gathering.
## Also, the task end callback for when a task completes.
##
###############################################################################

my ($_gather_ref, $_order_id, %_tmp);

sub _preserve_order {

   $_tmp{$_[1]} = $_[0];

   if (defined $_gather_ref) {
      while (1) {
         last unless exists $_tmp{$_order_id};
         push @{ $_gather_ref }, @{ delete $_tmp{$_order_id++} };
      }
   }
   else {
      $_order_id++;
   }

   return;
}

sub _task_end {

   my ($_mce, $_task_id, $_task_name) = @_;
   my $_pid = $_mce->{_init_pid}.'.'.$_mce->{_caller};

   if (defined $_mce->{user_tasks}->[$_task_id + 1]) {
      my $n_workers = $_mce->{user_tasks}->[$_task_id + 1]->{max_workers};
      my $_id = @{ $_queue->{$_pid} } - $_task_id - 1;

      $_queue->{$_pid}[$_id]->enqueue((undef) x $n_workers);
   }

   $_params->{task_end}->($_mce, $_task_id, $_task_name)
      if (exists $_params->{task_end} && ref $_params->{task_end} eq 'CODE');

   return;
}

###############################################################################
## ----------------------------------------------------------------------------
## Init and finish routines.
##
###############################################################################

sub MCE::Stream::_guard::DESTROY {
   my ($_pkg, $_id) = @{ $_[0] };

   if (defined $_pkg && $_id eq "$$.$_tid") {
      @{ $_[0] } = ();
      MCE::Stream->finish($_pkg);
   }

   return;
}

sub init (@) {

   shift if (defined $_[0] && $_[0] eq 'MCE::Stream');
   my $_pkg = "$$.$_tid.".caller();

   $_params->{$_pkg} = (ref $_[0] eq 'HASH') ? shift : { @_ };

   _croak("$_tag: (HASH) not allowed as input by this MCE model")
      if ( ref $_params->{$_pkg}{input_data} eq 'HASH' );

   @_ = ();

   defined wantarray
      ? bless([$_pkg, "$$.$_tid"], MCE::Stream::_guard::)
      : ();
}

sub finish (@) {

   shift if (defined $_[0] && $_[0] eq 'MCE::Stream');
   my $_pkg = (defined $_[0]) ? shift : "$$.$_tid.".caller();

   if ( $_pkg eq 'MCE' ) {
      for my $_k ( keys %{ $_MCE } ) { MCE::Stream->finish($_k, 1); }
   }
   elsif ( $_MCE->{$_pkg} && $_MCE->{$_pkg}{_init_pid} eq "$$.$_tid" ) {
      $_MCE->{$_pkg}->shutdown(@_) if $_MCE->{$_pkg}{_spawned};
      $_gather_ref = $_order_id = undef, undef %_tmp;

      delete $_user_tasks->{$_pkg};
      delete $_prev_c->{$_pkg};
      delete $_prev_m->{$_pkg};
      delete $_prev_n->{$_pkg};
      delete $_prev_w->{$_pkg};
      delete $_MCE->{$_pkg};

      if (defined $_queue->{$_pkg}) {
         local $_;
         $_->DESTROY() for (@{ $_queue->{$_pkg} });
         delete $_queue->{$_pkg};
      }
   }

   @_ = ();

   return;
}

###############################################################################
## ----------------------------------------------------------------------------
## Parallel stream with MCE -- file.
##
###############################################################################

sub run_file (@) {

   shift if (defined $_[0] && $_[0] eq 'MCE::Stream');

   my ($_file, $_pos); my $_start_pos = (ref $_[0] eq 'HASH') ? 2 : 1;
   my $_pid = "$$.$_tid.".caller();

   if (defined (my $_p = $_params->{$_pid})) {
      delete $_p->{input_data} if (exists $_p->{input_data});
      delete $_p->{sequence}   if (exists $_p->{sequence});
   }
   else {
      $_params->{$_pid} = {};
   }

   for my $_i ($_start_pos .. @_ - 1) {
      my $_r = ref $_[$_i];
      if ($_r eq '' || $_r eq 'SCALAR' || $_r =~ /^(?:GLOB|FileHandle|IO::)/) {
         $_file = $_[$_i]; $_pos = $_i;
         last;
      }
   }

   if (defined $_file && ref $_file eq '' && $_file ne '') {
      _croak("$_tag: ($_file) does not exist")      unless (-e $_file);
      _croak("$_tag: ($_file) is not readable")     unless (-r $_file);
      _croak("$_tag: ($_file) is not a plain file") unless (-f $_file);
      $_params->{$_pid}{_file} = $_file;
   }
   elsif (ref $_file eq 'SCALAR' || ref($_file) =~ /^(?:GLOB|FileHandle|IO::)/) {
      $_params->{$_pid}{_file} = $_file;
   }
   else {
      _croak("$_tag: (file) is not specified or valid");
   }

   if (defined $_pos) {
      pop @_ for ($_pos .. @_ - 1);
   }

   return run(@_);
}

###############################################################################
## ----------------------------------------------------------------------------
## Parallel stream with MCE -- sequence.
##
###############################################################################

sub run_seq (@) {

   shift if (defined $_[0] && $_[0] eq 'MCE::Stream');

   my ($_begin, $_end, $_pos); my $_start_pos = (ref $_[0] eq 'HASH') ? 2 : 1;
   my $_pid = "$$.$_tid.".caller();

   if (defined (my $_p = $_params->{$_pid})) {
      delete $_p->{sequence}   if (exists $_p->{sequence});
      delete $_p->{input_data} if (exists $_p->{input_data});
      delete $_p->{_file}      if (exists $_p->{_file});
   }
   else {
      $_params->{$_pid} = {};
   }

   for my $_i ($_start_pos .. @_ - 1) {
      my $_r = ref $_[$_i];

      if ($_r eq '' || $_r =~ /^Math::/ || $_r eq 'HASH' || $_r eq 'ARRAY') {
         $_pos = $_i;

         if ($_r eq '' || $_r =~ /^Math::/) {
            $_begin = $_[$_pos], $_end = $_[$_pos + 1];
            $_params->{$_pid}{sequence} = [
               $_[$_pos], $_[$_pos + 1], $_[$_pos + 2], $_[$_pos + 3]
            ];
         }
         elsif ($_r eq 'HASH') {
            $_begin = $_[$_pos]->{begin}, $_end = $_[$_pos]->{end};
            $_params->{$_pid}{sequence} = $_[$_pos];
         }
         elsif ($_r eq 'ARRAY') {
            $_begin = $_[$_pos]->[0], $_end = $_[$_pos]->[1];
            $_params->{$_pid}{sequence} = $_[$_pos];
         }

         last;
      }
   }

   _croak("$_tag: (sequence) is not specified or valid")
      unless (exists $_params->{$_pid}{sequence});
   _croak("$_tag: (begin) is not specified for sequence")
      unless (defined $_begin);
   _croak("$_tag: (end) is not specified for sequence")
      unless (defined $_end);

   $_params->{$_pid}{sequence_run} = undef;

   if (defined $_pos) {
      pop @_ for ($_pos .. @_ - 1);
   }

   return run(@_);
}

###############################################################################
## ----------------------------------------------------------------------------
## Parallel stream with MCE.
##
###############################################################################

sub run (@) {

   shift if (defined $_[0] && $_[0] eq 'MCE::Stream');

   my $_pkg = caller() eq 'MCE::Stream' ? caller(1) : caller();
   my $_pid = "$$.$_tid.$_pkg";

   if (ref $_[0] eq 'HASH' && !exists $_[0]->{code}) {
      $_params->{$_pid} = {} unless defined $_params->{$_pid};
      for my $_p (keys %{ $_[0] }) {
         $_params->{$_pid}{$_p} = $_[0]->{$_p};
      }

      shift;
   }

   my $_aref; $_aref = shift if (ref $_[0] eq 'ARRAY');

   $_order_id = 1; undef %_tmp;

   if (defined $_aref) {
      $_gather_ref = $_aref; @{ $_aref } = ();
   } else {
      $_gather_ref = undef;
   }

   ## -------------------------------------------------------------------------

   my (@_code, @_mode, @_name, @_wrks); my $_init_mce = 0; my $_pos = 0;
   my $_default_mode = $_def->{$_pkg}{DEFAULT_MODE};

   while (ref $_[0] eq 'CODE' || ref $_[0] eq 'HASH') {
      if (ref $_[0] eq 'CODE') {
         push @_code, $_[0];
         push @_mode, $_default_mode;
      }
      else {
         last if (!exists $_[0]->{code} && !exists $_[0]->{mode});

         push @_code, exists $_[0]->{code} ? $_[0]->{code} : undef;
         push @_mode, exists $_[0]->{mode} ? $_[0]->{mode} : $_default_mode;

         unless (ref $_code[-1] eq 'CODE') {
            @_ = (); _croak("$_tag: (code) is not valid");
         }
         if ($_mode[-1] ne 'grep' && $_mode[-1] ne 'map') {
            @_ = (); _croak("$_tag: (mode) is not valid");
         }
      }

      if (defined (my $_p = $_params->{$_pid})) {
         push @_name, (ref $_p->{task_name} eq 'ARRAY')
            ? $_p->{task_name}->[$_pos] : undef;
         push @_wrks, (ref $_p->{max_workers} eq 'ARRAY')
            ? $_p->{max_workers}->[$_pos] : undef;
      }

      $_init_mce = 1 if (
         !defined $_prev_c->{$_pid}[$_pos] ||
         $_prev_c->{$_pid}[$_pos] != $_code[$_pos]
      );
      $_init_mce = 1 if (
         !defined $_prev_m->{$_pid}[$_pos] ||
         $_prev_m->{$_pid}[$_pos] ne $_mode[$_pos]
      );

      $_init_mce = 1 if ($_prev_n->{$_pid}[$_pos] ne $_name[$_pos]);
      $_init_mce = 1 if ($_prev_w->{$_pid}[$_pos] ne $_wrks[$_pos]);

      $_prev_c->{$_pid}[$_pos] = $_code[$_pos];
      $_prev_m->{$_pid}[$_pos] = $_mode[$_pos];
      $_prev_n->{$_pid}[$_pos] = $_name[$_pos];
      $_prev_w->{$_pid}[$_pos] = $_wrks[$_pos];

      shift; $_pos++;
   }

   if (defined $_prev_c->{$_pid}[$_pos]) {
      pop @{ $_prev_c->{$_pid} } for ($_pos .. $#{ $_prev_c->{$_pid } });
      pop @{ $_prev_m->{$_pid} } for ($_pos .. $#{ $_prev_m->{$_pid } });
      pop @{ $_prev_n->{$_pid} } for ($_pos .. $#{ $_prev_n->{$_pid } });
      pop @{ $_prev_w->{$_pid} } for ($_pos .. $#{ $_prev_w->{$_pid } });

      $_init_mce = 1;
   }

   return unless (scalar @_code);

   ## -------------------------------------------------------------------------

   my $_input_data; my $_max_workers = $_def->{$_pkg}{MAX_WORKERS};
   my $_r = ref $_[0];

   if (@_ == 1 && $_r =~ /^(?:ARRAY|HASH|SCALAR|GLOB|FileHandle|IO::|Iterator::)/) {
      _croak("$_tag: (HASH) not allowed as input by this MCE model")
         if $_r eq 'HASH';
      $_input_data = shift;
   }

   if (defined (my $_p = $_params->{$_pid})) {
      $_max_workers = MCE::_parse_max_workers($_p->{max_workers})
         if (exists $_p->{max_workers} && ref $_p->{max_workers} ne 'ARRAY');

      delete $_p->{sequence}    if (defined $_input_data || scalar @_);
      delete $_p->{user_func}   if (exists $_p->{user_func});
      delete $_p->{user_tasks}  if (exists $_p->{user_tasks});
      delete $_p->{use_slurpio} if (exists $_p->{use_slurpio});
      delete $_p->{bounds_only} if (exists $_p->{bounds_only});
      delete $_p->{gather}      if (exists $_p->{gather});
   }

   if (@_code > 1 && $_max_workers > 1) {
      $_max_workers = int($_max_workers / @_code + 0.5) + 1;
   }

   my $_chunk_size = do {
      my $_p = $_params->{$_pid} || {};
      (defined $_p->{init_relay} || defined $_def->{$_pkg}{INIT_RELAY}) ? 1 :
      MCE::_parse_chunk_size(
         $_def->{$_pkg}{CHUNK_SIZE}, $_max_workers, $_params->{$_pid},
         $_input_data, scalar @_
      );
   };

   if (defined (my $_p = $_params->{$_pid})) {
      if (exists $_p->{_file}) {
         $_input_data = delete $_p->{_file};
      } else {
         $_input_data = $_p->{input_data} if exists $_p->{input_data};
      }
   }

   ## -------------------------------------------------------------------------

   MCE::_save_state($_MCE->{$_pid});

   if ($_init_mce || !exists $_queue->{$_pid}) {
      $_MCE->{$_pid}->shutdown() if (defined $_MCE->{$_pid});
      $_queue->{$_pid} = [] if (!defined $_queue->{$_pid});

      my $_Q = $_queue->{$_pid};
      pop(@{ $_Q })->DESTROY for (@_code .. @{ $_Q });

      push @{ $_Q }, MCE::Queue->new()
         for (@{ $_Q } .. @_code - 2);

      ## must clear arrays for nested session to work with Perl < v5.14
      _gen_user_tasks($_pid, $_Q, [@_code], [@_mode], [@_name], [@_wrks]);

      @_code = @_mode = @_name = @_wrks = ();

      my %_opts = (
         max_workers => $_max_workers, task_name => $_tag,
         user_tasks  => $_user_tasks->{$_pid}, task_end => \&_task_end,
         use_slurpio => 0,
      );

      if (defined (my $_p = $_params->{$_pid})) {
         local $_;

         for (keys %{ $_p }) {
            next if ($_ eq 'sequence_run');
            next if ($_ eq 'max_workers' && ref $_p->{max_workers} eq 'ARRAY');
            next if ($_ eq 'task_name' && ref $_p->{task_name} eq 'ARRAY');
            next if ($_ eq 'input_data');
            next if ($_ eq 'chunk_size');
            next if ($_ eq 'task_end');

            _croak("$_tag: ($_) is not a valid constructor argument")
               unless (exists $MCE::_valid_fields_new{$_});

            $_opts{$_} = $_p->{$_};
         }
      }

      for my $_k (qw/ tmp_dir freeze thaw init_relay use_threads /) {
         $_opts{$_k} = $_def->{$_pkg}{uc($_k)}
            if (exists $_def->{$_pkg}{uc($_k)} && !exists $_opts{$_k});
      }

      $_MCE->{$_pid} = MCE->new(pkg => $_pkg, %_opts);
   }
   else {
      ## Workers may persist after running. Thus, updating the MCE instance.
      ## These options do not require respawning.
      if (defined (my $_p = $_params->{$_pid})) {
         for my $_k (qw(
            RS interval stderr_file stdout_file user_error user_output
            job_delay submit_delay on_post_exit on_post_run user_args
            flush_file flush_stderr flush_stdout max_retries
         )) {
            $_MCE->{$_pid}{$_k} = $_p->{$_k} if (exists $_p->{$_k});
         }
      }
   }

   ## -------------------------------------------------------------------------

   if (defined $_input_data) {
      @_ = ();
      $_MCE->{$_pid}->process({ chunk_size => $_chunk_size }, $_input_data);
      delete $_MCE->{$_pid}{input_data};
   }
   elsif (scalar @_) {
      $_MCE->{$_pid}->process({ chunk_size => $_chunk_size }, \@_);
      delete $_MCE->{$_pid}{input_data};
   }
   else {
      if (defined $_params->{$_pid} && exists $_params->{$_pid}{sequence}) {
         $_MCE->{$_pid}->run({
             chunk_size => $_chunk_size,
             sequence   => $_params->{$_pid}{sequence}
         }, 0);
         if (exists $_params->{$_pid}{sequence_run}) {
             delete $_params->{$_pid}{sequence_run};
             delete $_params->{$_pid}{sequence};
         }
         delete $_MCE->{$_pid}{sequence};
      }
   }

   MCE::_restore_state();

   # destroy queue(s) if MCE::run requested workers to shutdown
   if (!$_MCE->{$_pid}{_spawned}) {
      $_->DESTROY() for @{ $_queue->{$_pid} };
      delete $_queue->{$_pid};
   }

   return map { @{ $_ } } delete @_tmp{ 1 .. $_order_id - 1 }
      unless (defined $_aref);

   $_gather_ref = undef;

   return;
}

###############################################################################
## ----------------------------------------------------------------------------
## Private methods.
##
###############################################################################

sub _croak {

   goto &MCE::_croak;
}

sub _gen_user_tasks {

   my ($_pid, $_queue_ref, $_code_ref, $_mode_ref, $_name_ref, $_wrks_ref) = @_;

   @{ $_user_tasks->{$_pid} } = ();

   ## For the code block farthest to the right.

   push @{ $_user_tasks->{$_pid} }, {
      task_name => $_name_ref->[-1],
      max_workers => $_wrks_ref->[-1],

      gather => (@{ $_code_ref } > 1)
         ? $_queue_ref->[-1] : \&_preserve_order,

      user_func => sub {
         my ($_mce, $_chunk_ref, $_chunk_id) = @_;
         my @_a; my $_code = $_code_ref->[-1];

         if (ref $_chunk_ref) {
            push @_a, ($_mode_ref->[-1] eq 'map')
               ?  map { &{ $_code } } @{ $_chunk_ref }
               : grep { &{ $_code } } @{ $_chunk_ref };
         }
         else {
            push @_a, ($_mode_ref->[-1] eq 'map')
               ?  map { &{ $_code } } $_chunk_ref
               : grep { &{ $_code } } $_chunk_ref;
         }

         MCE->gather( (@{ $_code_ref } > 1)
            ? MCE->freeze([ \@_a, $_chunk_id ])
            : (\@_a, $_chunk_id)
         );
      }
   };

   ## For in-between code blocks (processed from right to left).

   for (my $_i = @{ $_code_ref } - 2; $_i > 0; $_i--) {
      my $_pos = $_i;

      push @{ $_user_tasks->{$_pid} }, {
         task_name => $_name_ref->[$_pos],
         max_workers => $_wrks_ref->[$_pos],
         gather => $_queue_ref->[$_pos - 1],

         user_func => sub {
            my $_q = $_queue_ref->[$_pos];

            while (1) {
               my $_chunk = $_q->dequeue;
               last unless (defined $_chunk);

               my @_a; my $_code = $_code_ref->[$_pos];
               $_chunk = MCE->thaw($_chunk);

               push @_a, ($_mode_ref->[$_pos] eq 'map')
                  ?  map { &{ $_code } } @{ $_chunk->[0] }
                  : grep { &{ $_code } } @{ $_chunk->[0] };

               MCE->gather(MCE->freeze([ \@_a, $_chunk->[1] ]));
            }

            return;
         }
      };
   }

   ## For the left-most code block.

   if (@{ $_code_ref } > 1) {

      push @{ $_user_tasks->{$_pid} }, {
         task_name => $_name_ref->[0],
         max_workers => $_wrks_ref->[0],
         gather => \&_preserve_order,

         user_func => sub {
            my $_q = $_queue_ref->[0];

            while (1) {
               my $_chunk = $_q->dequeue;
               last unless (defined $_chunk);

               my @_a; my $_code = $_code_ref->[0];
               $_chunk = MCE->thaw($_chunk);

               push @_a, ($_mode_ref->[0] eq 'map')
                  ?  map { &{ $_code } } @{ $_chunk->[0] }
                  : grep { &{ $_code } } @{ $_chunk->[0] };

               MCE->gather(\@_a, $_chunk->[1]);
            }

            return;
         }
      };
   }

   return;
}

1;

__END__

###############################################################################
## ----------------------------------------------------------------------------
## Module usage.
##
###############################################################################

=head1 NAME

MCE::Stream - Parallel stream model for chaining multiple maps and greps

=head1 VERSION

This document describes MCE::Stream version 1.902

=head1 SYNOPSIS

 ## Exports mce_stream, mce_stream_f, mce_stream_s
 use MCE::Stream;

 my (@m1, @m2, @m3);

 ## Default mode is map and processed from right-to-left
 @m1 = mce_stream sub { $_ * 3 }, sub { $_ * 2 }, 1..10000;
 mce_stream \@m2, sub { $_ * 3 }, sub { $_ * 2 }, 1..10000;

 ## Native Perl
 @m3 = map { $_ * $_ } grep { $_ % 5 == 0 } 1..10000;

 ## Streaming grep and map in parallel
 mce_stream \@m3,
    { mode => 'map',  code => sub { $_ * $_ } },
    { mode => 'grep', code => sub { $_ % 5 == 0 } }, 1..10000;

 ## Array or array_ref
 my @a = mce_stream sub { $_ * $_ }, 1..10000;
 my @b = mce_stream sub { $_ * $_ }, \@list;

 ## Important; pass an array_ref for deeply input data
 my @c = mce_stream sub { $_->[1] *= 2; $_ }, [ [ 0, 1 ], [ 0, 2 ], ... ];
 my @d = mce_stream sub { $_->[1] *= 2; $_ }, \@deeply_list;

 ## File path, glob ref, IO::All::{ File, Pipe, STDIO } obj, or scalar ref
 ## Workers read directly and not involve the manager process
 my @e = mce_stream_f sub { chomp; $_ }, "/path/to/file"; # efficient

 ## Involves the manager process, therefore slower
 my @f = mce_stream_f sub { chomp; $_ }, $file_handle;
 my @g = mce_stream_f sub { chomp; $_ }, $io;
 my @h = mce_stream_f sub { chomp; $_ }, \$scalar;

 ## Sequence of numbers (begin, end [, step, format])
 my @i = mce_stream_s sub { $_ * $_ }, 1, 10000, 5;
 my @j = mce_stream_s sub { $_ * $_ }, [ 1, 10000, 5 ];

 my @k = mce_stream_s sub { $_ * $_ }, {
    begin => 1, end => 10000, step => 5, format => undef
 };

=head1 DESCRIPTION

This module allows one to stream multiple map and/or grep operations in
parallel. Code blocks run simultaneously from right-to-left. The results
are appended immediately when providing a reference to an array.

 ## Appends are serialized, even out-of-order ok, but immediately.
 ## Out-of-order chunks are held temporarily until ordered chunks
 ## arrive.

 mce_stream \@a, sub { $_ }, sub { $_ }, sub { $_ }, 1..10000;

 ##                                                    input
 ##                                        chunk1      input
 ##                            chunk3      chunk2      input
 ##                chunk2      chunk2      chunk3      input
 ##   append1      chunk3      chunk1      chunk4      input
 ##   append2      chunk1      chunk5      chunk5      input
 ##   append3      chunk5      chunk4      chunk6      ...
 ##   append4      chunk4      chunk6      ...
 ##   append5      chunk6      ...
 ##   append6      ...
 ##   ...
 ##

MCE incurs a small overhead due to passing of data. A fast code block will
run faster natively when chaining multiple map functions. However, the
overhead will likely diminish as the complexity increases for the code.

 ## 0.334 secs -- baseline using the native map function
 my @m1 = map { $_ * 4 } map { $_ * 3 } map { $_ * 2 } 1..1000000;

 ## 0.427 secs -- this is quite amazing considering data passing
 my @m2 = mce_stream
       sub { $_ * 4 }, sub { $_ * 3 }, sub { $_ * 2 }, 1..1000000;

 ## 0.355 secs -- appends to @m3 immediately, not after running
 my @m3; mce_stream \@m3,
       sub { $_ * 4 }, sub { $_ * 3 }, sub { $_ * 2 }, 1..1000000;

Even faster is mce_stream_s; useful when input data is a range of numbers.
Workers generate sequences mathematically among themselves without any
interaction from the manager process. Two arguments are required for
mce_stream_s (begin, end). Step defaults to 1 if begin is smaller than end,
otherwise -1.

 ## 0.278 secs -- numbers are generated mathematically via sequence
 my @m4; mce_stream_s \@m4,
       sub { $_ * 4 }, sub { $_ * 3 }, sub { $_ * 2 }, 1, 1000000;

=head1 OVERRIDING DEFAULTS

The following list options which may be overridden when loading the module.
The fast option is obsolete in 1.867 onwards; ignored if specified.

 use Sereal qw( encode_sereal decode_sereal );
 use CBOR::XS qw( encode_cbor decode_cbor );
 use JSON::XS qw( encode_json decode_json );

 use MCE::Stream
     max_workers => 8,                # Default 'auto'
     chunk_size => 500,               # Default 'auto'
     tmp_dir => "/path/to/app/tmp",   # $MCE::Signal::tmp_dir
     freeze => \&encode_sereal,       # \&Storable::freeze
     thaw => \&decode_sereal,         # \&Storable::thaw
     init_relay => 0,                 # Default undef; MCE 1.882+
     use_threads => 0,                # Default undef; MCE 1.882+
     default_mode => 'grep',          # Default 'map'
 ;

From MCE 1.8 onwards, Sereal 3.015+ is loaded automatically if available.
Specify C<< Sereal => 0 >> to use Storable instead.

 use MCE::Stream Sereal => 0;

=head1 CUSTOMIZING MCE

=over 3

=item MCE::Stream->init ( options )

=item MCE::Stream::init { options }

=back

The init function accepts a hash of MCE options. The gather and bounds_only
options, if specified, are ignored due to being used internally by the
module (not shown below).

In scalar context (API available since 1.897), call C<MCE::Stream->finish>
automatically upon leaving the scope or program.

 use MCE::Stream;

 my $guard = MCE::Stream->init(
    chunk_size => 1, max_workers => 4,

    user_begin => sub {
       print "## ", MCE->wid, " started\n";
    },

    user_end => sub {
       print "## ", MCE->wid, " completed\n";
    }
 );

 my @a = mce_stream sub { $_ * $_ }, 1..100;

 print "\n", "@a", "\n";

 -- Output

 ## 1 started
 ## 2 started
 ## 3 started
 ## 4 started
 ## 3 completed
 ## 1 completed
 ## 2 completed
 ## 4 completed

 1 4 9 16 25 36 49 64 81 100 121 144 169 196 225 256 289 324 361
 400 441 484 529 576 625 676 729 784 841 900 961 1024 1089 1156
 1225 1296 1369 1444 1521 1600 1681 1764 1849 1936 2025 2116 2209
 2304 2401 2500 2601 2704 2809 2916 3025 3136 3249 3364 3481 3600
 3721 3844 3969 4096 4225 4356 4489 4624 4761 4900 5041 5184 5329
 5476 5625 5776 5929 6084 6241 6400 6561 6724 6889 7056 7225 7396
 7569 7744 7921 8100 8281 8464 8649 8836 9025 9216 9409 9604 9801
 10000

Like with MCE::Stream->init above, MCE options may be specified using an
anonymous hash for the first argument. Notice how both max_workers and
task_name can take an anonymous array for setting values uniquely
per each code block.

Remember that MCE::Stream processes from right-to-left when setting the
individual values.

 use MCE::Stream;

 my @a = mce_stream {
    task_name   => [ 'c', 'b', 'a' ],
    max_workers => [  2,   4,   3, ],

    user_end => sub {
       my ($mce, $task_id, $task_name) = @_;
       print "$task_id - $task_name completed\n";
    },

    task_end => sub {
       my ($mce, $task_id, $task_name) = @_;
       MCE->print("$task_id - $task_name ended\n");
    }
 },
 sub { $_ * 4 },             ## 2 workers, named c
 sub { $_ * 3 },             ## 4 workers, named b
 sub { $_ * 2 }, 1..10000;   ## 3 workers, named a

 -- Output

 0 - a completed
 0 - a completed
 0 - a completed
 0 - a ended
 1 - b completed
 1 - b completed
 1 - b completed
 1 - b completed
 1 - b ended
 2 - c completed
 2 - c completed
 2 - c ended

Note that the anonymous hash, for specifying options, also comes first when
passing an array reference.

 my @a; mce_stream {
    ...
 }, \@a, sub { ... }, sub { ... }, 1..10000;

=head1 API DOCUMENTATION

Scripts using MCE::Stream can be written using the long or short form.
The long form becomes relevant when mixing modes. Again, processing
occurs from right-to-left.

 my @m3 = mce_stream
    { mode => 'map',  code => sub { $_ * $_ } },
    { mode => 'grep', code => sub { $_ % 5 == 0 } }, 1..10000;

 my @m4; mce_stream \@m4,
    { mode => 'map',  code => sub { $_ * $_ } },
    { mode => 'grep', code => sub { $_ % 5 == 0 } }, 1..10000;

For multiple grep blocks, the short form can be used. Simply specify the
default mode for the module. The two valid values for default_mode is 'grep'
and 'map'.

 use MCE::Stream default_mode => 'grep';

 my @f = mce_stream_f sub { /ending$/ }, sub { /^starting/ }, $file;

The following assumes 'map' for default_mode in order to demonstrate all the
possibilities for providing input data.

=over 3

=item MCE::Stream->run ( sub { code }, list )

=item mce_stream sub { code }, list

=back

Input data may be defined using a list or an array reference. Unlike MCE::Loop,
Flow, and Step, specifying a hash reference as input data isn't allowed.

 ## Array or array_ref
 my @a = mce_stream sub { $_ * 2 }, 1..1000;
 my @b = mce_stream sub { $_ * 2 }, \@list;

 ## Important; pass an array_ref for deeply input data
 my @c = mce_stream sub { $_->[1] *= 2; $_ }, [ [ 0, 1 ], [ 0, 2 ], ... ];
 my @d = mce_stream sub { $_->[1] *= 2; $_ }, \@deeply_list;

 ## Not supported
 my @z = mce_stream sub { ... }, \%hash;

=over 3

=item MCE::Stream->run_file ( sub { code }, file )

=item mce_stream_f sub { code }, file

=back

The fastest of these is the /path/to/file. Workers communicate the next offset
position among themselves with zero interaction by the manager process.

C<IO::All> { File, Pipe, STDIO } is supported since MCE 1.845.

 my @c = mce_stream_f sub { chomp; $_ . "\r\n" }, "/path/to/file";  # faster
 my @d = mce_stream_f sub { chomp; $_ . "\r\n" }, $file_handle;
 my @e = mce_stream_f sub { chomp; $_ . "\r\n" }, $io;              # IO::All
 my @f = mce_stream_f sub { chomp; $_ . "\r\n" }, \$scalar;

=over 3

=item MCE::Stream->run_seq ( sub { code }, $beg, $end [, $step, $fmt ] )

=item mce_stream_s sub { code }, $beg, $end [, $step, $fmt ]

=back

Sequence may be defined as a list, an array reference, or a hash reference.
The functions require both begin and end values to run. Step and format are
optional. The format is passed to sprintf (% may be omitted below).

 my ($beg, $end, $step, $fmt) = (10, 20, 0.1, "%4.1f");

 my @f = mce_stream_s sub { $_ }, $beg, $end, $step, $fmt;
 my @g = mce_stream_s sub { $_ }, [ $beg, $end, $step, $fmt ];

 my @h = mce_stream_s sub { $_ }, {
    begin => $beg, end => $end, step => $step, format => $fmt
 };

=over 3

=item MCE::Stream->run ( { input_data => iterator }, sub { code } )

=item mce_stream { input_data => iterator }, sub { code }

=back

An iterator reference may be specified for input_data. The only other way
is to specify input_data via MCE::Stream->init. This prevents MCE::Stream
from configuring the iterator reference as another user task which will
not work.

Iterators are described under section "SYNTAX for INPUT_DATA" at L<MCE::Core>.

 MCE::Stream->init(
    input_data => iterator
 );

 my @a = mce_stream sub { $_ * 3 }, sub { $_ * 2 };

=head1 MANUAL SHUTDOWN

=over 3

=item MCE::Stream->finish

=item MCE::Stream::finish

=back

Workers remain persistent as much as possible after running. Shutdown occurs
automatically when the script terminates. Call finish when workers are no
longer needed.

 use MCE::Stream;

 MCE::Stream->init(
    chunk_size => 20, max_workers => 'auto'
 );

 my @a = mce_stream { ... } 1..100;

 MCE::Stream->finish;

=head1 INDEX

L<MCE|MCE>, L<MCE::Core>

=head1 AUTHOR

Mario E. Roy, S<E<lt>marioeroy AT gmail DOT comE<gt>>

=cut