RFR: 8345314: Add a red–black tree as a utility data structure [v3]

[Afshin Zafari]

On Tue, 3 Dec 2024 12:51:18 GMT, Casper Norrbin <cnorrbin at openjdk.org> wrote:

>> Hi everyone,
>> 
>> This effort began as an exploration of replacing the current NMT treap with a red-black tree. Along the way, I discovered that others were also interested in having a general-purpose tree structure available within HotSpot.
>> 
>> The red-black tree is designed to serve as a drop-in replacement for the existing NMT treap, keeping a nearly identical interface. However, I’ve also added a few additional requested features, such as an iterator.
>> 
>> Testing builds off the treap tests, adding a few extra that inserts/removes and checks that the tree is correct. Testing uses the function `verify_self`, which iterates over the tree and checks that all red-black tree properties hold. Additionally, the tree has been tested in vmatree instead of the treap without any errors.
>> 
>> For those who may want to revisit the fundamentals of red-black trees, [Wikipedia](https://en.wikipedia.org/wiki/Red%E2%80%93black_tree) offers a great summary with tables covering the various balancing cases. Alternatively, your favorite data structure book could provide even more insight.
>
> Casper Norrbin has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fixed nmt tag

test/hotspot/gtest/utilities/test_rbtree.cpp line 313:

> 311:     for (int i = 0; i < size; i++) {
> 312:       int r = os::random() % size;
> 313:       allocations.append(r % size);

`... % size` is already done in previous line.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/22360#discussion_r1871855177