use strict; use warnings; use feature 'say'; use MCE::Flow; sub collatz_choroba { my ($n) = @_; my @seq = $n; push @seq, ( $seq[-1] >> 1, 3 * $seq[-1] + 1 )[ $seq[-1] % 2 ] while $seq[-1] != 1; return scalar @seq; } sub collatz_1nickt { my ($n) = @_; my @seq = $n; push @seq, $n = $n % 2 ? 3 * $n + 1 : $n >> 1 while $n != 1; return scalar @seq; } sub collatz_compress { my ($n) = @_; my @seq = $n; # Notation and compressed dynamics (2:15 into the video) # https://www.youtube.com/watch?v=t1I9uHF9X5Y # consider the map # C(x) = $n % 2 ? 3 * $n + 1 : $n / 2 # compress the map to the dynamically equivalent # T(x) = $n % 2 ? (3 * $n + 1) / 2 : $n / 2 # compress loop iteration when odd sequence push @seq, $n % 2 ? ( $n = 3 * $n + 1, $n = $n >> 1 ) : ( $n = $n >> 1 ) while $n != 1; return scalar @seq; } sub collatz_count { my ($n) = @_; my $steps = 1; # count using the T(x) notation $n % 2 ? ( $steps += 2, $n = (3 * $n + 1) >> 1 ) : ( $steps += 1, $n = $n >> 1 ) while $n != 1; return $steps; } #*collatz = \&collatz_choroba; # choose collatz here #*collatz = \&collatz_1nickt; #*collatz = \&collatz_compress; *collatz = \&collatz_count; my @sizes; MCE::Flow->init( max_workers => MCE::Util::get_ncpu(), gather => \@sizes, bounds_only => 1, ); mce_flow_s sub { my ($start, $end) = @{ $_[1] }; my @ret = map { [ $_, collatz($_) ] } $start .. $end; MCE->gather( ( sort { $b->[1] <=> $a->[1] } @ret )[ 0..19 ] ); }, 1, 1e6; MCE::Flow->finish; say "@$_" for ( sort { $b->[1] <=> $a->[1] } @sizes )[ 0..19 ];