1e7: serial 15.311s 1 core parallel 7.898s 2 cores parallel 4.229s 4 cores parallel 2.244s 8 cores parallel 1.265s 16 cores parallel 0.815s 32 cores 1e8: serial 2m38.645s 1 core parallel 11.779s 32 cores before: serial qsorti parallel 6.652s 32 cores after : parallel qsorti parallel 2.656s 32 cores non-PDL solution parallel 1.644s 32 cores non-PDL solution with Inline::C https://perlmonks.org/?node_id=11115780 Collatz(63728127) has sequence length of 950 steps Collatz(95592191) has sequence length of 948 steps Collatz(96883183) has sequence length of 811 steps Collatz(86010015) has sequence length of 798 steps Collatz(98110761) has sequence length of 749 steps Collatz(73583070) has sequence length of 746 steps Collatz(73583071) has sequence length of 746 steps Collatz(36791535) has sequence length of 745 steps Collatz(55187303) has sequence length of 743 steps Collatz(56924955) has sequence length of 743 steps Collatz(82780955) has sequence length of 741 steps Collatz(85387433) has sequence length of 741 steps Collatz(63101607) has sequence length of 738 steps Collatz(64040575) has sequence length of 738 steps Collatz(93128574) has sequence length of 736 steps Collatz(93128575) has sequence length of 736 steps Collatz(94652411) has sequence length of 736 steps Collatz(96060863) has sequence length of 736 steps Collatz(46564287) has sequence length of 735 steps Collatz(69846431) has sequence length of 733 steps