Implement bounded iterators for BTree #20082

pczarn · 2014-12-20T18:56:48Z

Part of collections reform v1, #18424
Also, iteration is simplified:

before
test btree::map::bench::iter_1000                          ... bench:     17177 ns/iter (+/- 6302)
test btree::map::bench::iter_100000                        ... bench:   1735731 ns/iter (+/- 23908)
test btree::map::bench::iter_20                            ... bench:       386 ns/iter (+/- 148)
after
test btree::map::bench::iter_1000                          ... bench:     15777 ns/iter (+/- 346)
test btree::map::bench::iter_100000                        ... bench:   1602604 ns/iter (+/- 73629)
test btree::map::bench::iter_20                            ... bench:       339 ns/iter (+/- 91)

cc @gereeter @cgaebel
r? @gankro

cgaebel · 2014-12-20T19:10:01Z

src/libcollections/btree/node.rs

@@ -1376,7 +1381,7 @@ struct AbsTraversal<Impl> {

 /// A single atomic step in a traversal. Either an element is visited, or an edge is followed
 pub enum TraversalItem<K, V, E> {
-    Elem(K, V),
+    Elem((K, V)),


Just for convenient interop with iterators?

For the obscure opt.map(Elem). Ah, I should add a comment there.

cgaebel · 2014-12-20T19:15:16Z

Can I see tests that look like the iter tests, but bounded? Just make sure they iterate over the same number of elements. I suspect it'd be an interesting comparison. Specifically, I'm looking to see what the cost of creating the iterator looks like.

cgaebel · 2014-12-20T19:17:20Z

src/libcollections/btree/map.rs

+}
+
+/// An endpoint of a range of keys.
+pub enum Bound<T> {


I feel like this shouldn't live in this file. Maybe it should go in libcore? I don't know. It just doesn't seem specific to BTrees.

Agreed. I recommend moving it to the root of libcollections (and std::collections as a re-export).

Gankra · 2014-12-21T00:01:07Z

Quick skim: interesting approach! Excited to dig into this. Sad to see macros. :(

Will review monday if no one else does first.

cgaebel · 2014-12-21T04:55:34Z

Haha "sad to see macros" is pretty much exactly what I thought when scrolling through this.

pczarn · 2014-12-21T12:59:46Z

Should we provide RangedKeys, RangedValues, RangedValuesMut for map, as well as ~~RangedItems~~ RangedKeys for BTreeSet?

interesting approach!

Can you think of some other approach?

Unfortunately, the code is quadrupled for both ends and mut/immutable. Macros deal with the latter duplication.

Gankra · 2014-12-22T15:44:56Z

I was assuming you were going to replace the Two RingBufs with two Vecs, which should better optimize for the "average" case. In fact you've kind've done that. Two stacks and a deque are famously "equivalent", although normally I see that used to implement a deque using two stacks, not the other way around :P

The code complexity benefits probably make it worth it, though.

Gankra · 2014-12-22T15:49:57Z

src/libcollections/btree/map.rs

-                Push(item) => { self.left.push_back(item); },
-                Pop => { self.left.pop_back(); },
+                Push(item) => { self.traversals.push_back(item); },
+                Pop => { self.traversals.pop_back(); },
            }


;_; so elegant

Gankra · 2014-12-30T04:26:54Z

src/libcollections/btree/node.rs

+            self.head_is_edge = true;
+            self.inner.next_kv().map(Elem)
+        })
+    }


Smooth. 💖

Gankra · 2014-12-30T04:37:08Z

Just need to fully parse the macro madness...

Gankra · 2014-12-30T04:43:24Z

src/libcollections/btree/map.rs

+                    loop {
+                        let slice = lca.slice_from(min_key).slice_to(max_key);
+                        match slice.edges {
+                            [ref $($m)* edge] => lca = edge.$as_slices_internal(),


Trying to understand this: basically you make a subslice, and if it contains a single edge you conclude that you must descend deeper? Otherwise (including the case where it's empty?), this must be the LCA?

As always: would love some more docs as to what's going on here.

Gankra · 2015-01-04T03:40:19Z

Basically r=me (feel free to squash), but this is complex enough that I'd appreciate a secondary review from @huonw or @gereeter (or anyone else, really).

Also needs another rebase :(

pczarn · 2015-01-04T23:55:06Z

@gankro, done. The comment "for ranges such as..." is irrelevant for the main example.

pczarn · 2015-01-05T00:22:16Z

src/libcollections/btree/map.rs

+                    // lca represents the Lowest Common Ancestor, above which we never
+                    // walk, since everything else is outside the range to iterate.
+                    //       ___________________
+                    //      |__0_|_80_|_85_|_90_|  (root)


I suppose you wouldn't like to have that irrelevant part. Removed.

emberian · 2015-01-05T06:46:20Z

Needs another rebase :(

pczarn · 2015-01-07T22:37:34Z

@gankro Tested, rebased (in this order 😅 )

Gankra · 2015-01-09T18:44:50Z

@pczarn needs some changes for old_impl_check stuff, I guess?

pczarn · 2015-01-14T15:27:42Z

Updated for old_impl_check

Gankra · 2015-01-19T04:44:48Z

Seems this didn't satisfy all the impl check issues.

Simplify BTree's iterators, too.

pczarn · 2015-01-19T16:49:11Z

@gankro Updated

Gankra · 2015-01-19T16:52:27Z

@bors r+ 429c

Gankra · 2015-01-19T16:53:59Z

Actually this is some pretty hairy stuff.

@bors p=0

?

Gankra · 2015-01-19T16:57:57Z

Aha.

@bors rollup-

bors · 2015-01-19T17:43:47Z

⌛ Testing commit 429c23d with merge 54c9a46...

@gereeter

Part of collections reform v1, #18424 Also, iteration is simplified: ``` before test btree::map::bench::iter_1000 ... bench: 17177 ns/iter (+/- 6302) test btree::map::bench::iter_100000 ... bench: 1735731 ns/iter (+/- 23908) test btree::map::bench::iter_20 ... bench: 386 ns/iter (+/- 148) after test btree::map::bench::iter_1000 ... bench: 15777 ns/iter (+/- 346) test btree::map::bench::iter_100000 ... bench: 1602604 ns/iter (+/- 73629) test btree::map::bench::iter_20 ... bench: 339 ns/iter (+/- 91) ``` cc @gereeter @cgaebel r? @gankro

bors · 2015-01-19T19:40:48Z

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-win-32-nopt-t, auto-win-32-opt, auto-win-64-nopt-t, auto-win-64-opt

rust-highfive assigned Gankra Dec 20, 2014

cgaebel reviewed Dec 20, 2014
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pczarn force-pushed the btree-bounded-iter branch from b3496c9 to d199ddb Compare December 21, 2014 15:38

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pczarn force-pushed the btree-bounded-iter branch 4 times, most recently from 4402b6a to d4e6d3d Compare December 23, 2014 22:43

Gankra reviewed Dec 30, 2014
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src/libcollections/btree/node.rs

self.head_is_edge = true;

self.inner.next_kv().map(Elem)

})

}

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Smooth. 💖

Gankra reviewed Dec 30, 2014
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Nemo157 mentioned this pull request Jan 3, 2015

Implement Bounded Iterator RoaringBitmap/roaring-rs#5

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pczarn force-pushed the btree-bounded-iter branch 2 times, most recently from 7168297 to 31531c6 Compare January 4, 2015 23:54

pczarn force-pushed the btree-bounded-iter branch from 31531c6 to 1f62517 Compare January 5, 2015 00:20

pczarn reviewed Jan 5, 2015
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pczarn force-pushed the btree-bounded-iter branch 3 times, most recently from c91326e to 3ee4dc0 Compare January 7, 2015 22:08

pczarn force-pushed the btree-bounded-iter branch from 3ee4dc0 to fe6cca3 Compare January 14, 2015 15:25

pczarn force-pushed the btree-bounded-iter branch from fe6cca3 to cf2a2ab Compare January 19, 2015 16:48

Implement range and range_mut for BTree

429c23d

Simplify BTree's iterators, too.

pczarn force-pushed the btree-bounded-iter branch from cf2a2ab to 429c23d Compare January 19, 2015 16:49

bors merged commit 429c23d into rust-lang:master Jan 19, 2015

pczarn deleted the btree-bounded-iter branch January 24, 2015 09:22

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Implement bounded iterators for BTree #20082

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