raku - 馈送运算符(operator)管道的行为

Question

我正在使用以下代码试验提要运算符:

my $limit=10000000;
my $list=(0,1...4);
sub task($_,$name) {
    say "Start $name on $*THREAD";
    loop ( my $i=0; $i < $limit; $i++ ){};
    say "End $name";
    Nil;
}

sub stage( &code, *@elements --> Seq) {
    map(&code,  @elements);
}

sub feeds() {
    my @results;
    $list
    ==> map ({ task($_, "stage 1"); say( now - ENTER now );$_+1})
    ==> map ({ task($_, "stage 2"); say( now - ENTER now );$_+1})
    ==> stage ({ task($_, "stage 3"); say( now - ENTER now );$_+1}) 
    ==> @results;

    say @results;
}

feeds();

任务子只是一个循环来燃烧cpu周期并显示使用的线程

stage sub 是 map sub

的包装器

馈送管道的每一步都映射到调用 CPU 密集型任务并对其计时。映射的结果是输入+1

运行时的输出是:

Start stage 1 on Thread<1>(Initial thread)
End stage 1
0.7286811
Start stage 2 on Thread<1>(Initial thread)
End stage 2
0.59053989
Start stage 1 on Thread<1>(Initial thread)
End stage 1
0.5955893
Start stage 2 on Thread<1>(Initial thread)
End stage 2
0.59050998
Start stage 1 on Thread<1>(Initial thread)
End stage 1
0.59472201
Start stage 2 on Thread<1>(Initial thread)
End stage 2
0.5968531
Start stage 1 on Thread<1>(Initial thread)
End stage 1
0.5917188
Start stage 2 on Thread<1>(Initial thread)
End stage 2
0.587358
Start stage 1 on Thread<1>(Initial thread)
End stage 1
0.58689858
Start stage 2 on Thread<1>(Initial thread)
End stage 2
0.59177099
Start stage 3 on Thread<1>(Initial thread)
End stage 3
3.8549498
Start stage 3 on Thread<1>(Initial thread)
End stage 3
3.8560015
Start stage 3 on Thread<1>(Initial thread)
End stage 3
3.77634317
Start stage 3 on Thread<1>(Initial thread)
End stage 3
3.6754558
Start stage 3 on Thread<1>(Initial thread)
End stage 3
3.672909
[3 4 5 6 7]

结果在 @result是正确的(来自 $list 的输入增加了 3 三倍)

前两个阶段的输出拉动/交替，但第三阶段直到第 2 阶段的所有输入完成后才执行

我的 map 子包装器是否存在问题导致此行为？

此外，在包装器中进行评估所需的时间明显长于直接调用 map。

任何帮助表示赞赏。

Answer 1

slurpy 参数正在等待消耗传递给它的整个序列。考虑以下区别:

perl6 -e 'sub foo($) { }; my $items := gather for 1..Inf { say $_ }; foo($items);'

perl6 -e 'sub foo(*@) { }; my $items := gather for 1..Inf { say $_ }; foo($items);'

第一个例子会结束，第二个永远不会结束。因此，您希望将舞台功能更改为:

sub stage( &code, $elements --> Seq) {
    map(&code,  $elements);
}