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// Test performance of a task "spawn ladder", in which children task have many
// many ancestor taskgroups, but with only a few such groups alive at a time.
// Each child task has to enlist as a descendant in each of its ancestor
// groups, but that shouldn't have to happen for already-dead groups.
//
// The filename is a song reference; google it in quotes.
fn child_generation(gens_left: uint, -c: pipes::Chan<()>) {
// This used to be O(n^2) in the number of generations that ever existed.
// With this code, only as many generations are alive at a time as tasks
// alive at a time,
let c = ~mut Some(c);
do task::spawn_supervised {
let c = option::swap_unwrap(c);
if gens_left & 1 == 1 {
task::yield(); // shake things up a bit
}
if gens_left > 0 {
child_generation(gens_left - 1, c); // recurse
} else {
c.send(())
}
}
}
fn main() {
let args = os::args();
let args = if os::getenv(~"RUST_BENCH").is_some() {
~[~"", ~"100000"]
} else if args.len() <= 1u {
~[~"", ~"100"]
} else {
copy args
};
let (c,p) = pipes::stream();
child_generation(uint::from_str(args[1]).get(), c);
if p.try_recv().is_none() {
fail ~"it happened when we slumbered";
}
}
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