# New Ticket Created by Alex Jakimenko
# Please include the string: [perl #127452]
# in the subject line of all future correspondence about this issue.
# <URL: https://rt.perl.org/Ticket/Display.html?id=127452 >
Let's try running the same code twice:
<AlexDaniel> m: my @x = ^10; my @y = @x.hyper(:3batch, :5degree).map: {
sleep rand / 100000; $_ + 1 }; say @y
<camelia> rakudo-moar a5fe34: OUTPUT«[]»
<AlexDaniel> m: my @x = ^10; my @y = @x.hyper(:3batch, :5degree).map: {
sleep rand / 100000; $_ + 1 }; say @y
<camelia> rakudo-moar a5fe34: OUTPUT«[1 2 3 4 5 6 7 8 9 10]»
The thing is that sometimes ｢hyper｣ decides to return an empty list. This
is a real problem because it basically renders it useless (too unreliable).
If you have problems reproducing it, try changing ｢/ 100000｣ to something
else. This delay is not really relevant but it seems like it affects the
chances to get one result or another.
Here's also a golfed down version:
Code:
dd @(^10 .hyper(:1batch).map: { sleep rand; $_ })
Result:
()
OR
(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
According to the execution time ｢hyper｣ does not even bother to compute the
result in these problematic cases (it just returns an empty list without
trying to process the data). That being said, there is a chance that it
fails half way through, see next example.
Another interesting issue (probably the same one):
Code:
.say for (^10).hyper(:1batch).map: { sleep rand; $_ }
Result:
1
OR
2
OR
3
OR
0
3
2
1
5
8
7
4
6
9
OR etc.
So not only it is out of order (#127099), but it is also extremely broken.
It looks like there is no such problem with ｢race｣.
IRC log (nothing useful there though):
http://irclog.perlgeek.de/perl6/2016-02-02#i_11975794
