the results are very interesting...

The kikuchiyou.pl script not involving IPC should be first. It's a great solution. If memory is plentiful, why not consume a little memory for input data before spawning.

The tests ran in a loop utilizing 8, 16, 32, etc up to 4096 threads...

It's interesting seeing one attempting 4,000+ workers for a use-case that is somewhat CPU-bound. On another note, what coolness witnessing the operating system coping with this. For example, the threads and MCE::Child solutions involve IPC; e.g. workers entering a critical section -- who's next to read input from the queue or channel.

On my system, the kikuchiyo.pl script exits early running 512 workers. I modified the script to figure why that is.

--- kikuchiyo1.pl    2023-01-27 23:31:34.592261566 -0600
+++ kikuchiyo2.pl    2023-01-27 23:31:12.488762580 -0600
@@ -92,12 +92,16 @@
 for my $worker_id (0..$maxforks-1) {
     if (my $pid = fork) {
         ++$forkcount;
+    } elsif (!defined $pid) {
+        warn "fork failed for worker_id $worker_id\n";
     } else {
         for my $i (0..$#{$batched_data[$worker_id]}) {
             my $infile = $batched_data[$worker_id][$i];
             my $subdir = $worker_id + 1;
-            open my $IN, '<', $infile or exit(0);
-            open my $OUT, '>', "$tempdir/$subdir/text-$i" or exit(0);
+            open my $IN, '<', $infile
+                or die "[$worker_id] open error: infile";
+            open my $OUT, '>', "$tempdir/$subdir/text-$i"
+                or die "[$worker_id] open error: outfile\n";
             while (<$IN>) {
                 tr/-!"#%&()*',.\/:;?@\[\\\]”_“{’}><^)(|/ /; # no punc
+t "
                 s/^/ /;
[download]

Possibly a ulimit issue -n issue. My open-files ulimit is 1024. Edit: It has nothing to do with ulimit as the number of open files ulimit is per process. Workers 256+ exit early.

[256] open error: outfile
[257] open error: outfile
[258] open error: outfile
...
[511] open error: outfile
[download]

The threads and MCE::Child solutions pass for 512 workers. Again, regex is used here -- kinda CPU bound. Is running more workers than the number of logical CPU cores improving performance? There are golden CPU samples out there.