On Tue, 21 May 2024, Ion Gaztañaga via Boost wrote:
Lately I've been collecting some ideas about how to improve the library and
keep it interesting/useful both for other Boost libraries and Boost users.
I've somewhat formalized a bit some of those ideas and I'd like to share them
here in order to obtain feedback from the developers. Here's the document:
https://docs.google.com/document/d/1VdMTheFUczC946dP3VKPseOoUq3sVKjU73oMvK8F...
Note that this document does not outline a schedule for all those ideas, it's
an initial description of possible developments that should be
evaluated/prioritized, as developing a substantial subset of the proposals
would be a huge task.
Thanks in advance for your attention and comments.
Hello,
since you are asking, here are some comments as a user.
Performance:
You already have #248 about a performance regression in flat_map. It can
currently be twice as fast to use a struct { int key; mutable int value; }
in a flat_set than a flat_map.
I would prioritize fixing known performance issues before looking for
others, but I guess it is a worthy goal.
Debug:
Not that important to me.
New structures:
- Among what you propose, I may be interested in the B/T-trees and the
skip lists, if their performance turns out to be worth it. For hive, if
the existing implementation can be included in boost with only minor
tweaks, why not. Otherwise, if hive gets standardized and standard
library vendors don't mess up their implementation too much, having a
version in boost doesn't seem worth the trouble, or at least it is less
interesting than having structures not present in the standard. segtor:
for the longest time I thought deque used blocks of varying size... It
looks interesting, but I am not sure I would actually use it.
- https://en.wikipedia.org/wiki/Order_statistic_tree (it could be a new
option in an existing container or at least share a lot of code with
other trees)
- vector optimized for the empty case: I was going to suggest it, but I
now see you have added it to the document since the initial post :-)
Improvements:
For performance, it is often useful to provide an allocator to node-based
structures like list and set. A well-tuned allocator may want to know the
size of the nodes in advance (preferably at compile-time, not wait for the
first call to allocate()). However, this information can be very
inconvenient to access. If you could provide a simple, reliable way to
extract this information (one that still works if a user defines recursive
maps or other complicated cases with incomplete types), that would be
great.
Document a way to go from a pointer to an iterator in set and other
datastructures. Maybe we only needed that because we didn't know about the
advanced options of intrusive lists at the time, but for a map whose
values are connected through intrusive linked lists, we had to write
fragile code
(https://github.com/GUDHI/gudhi-devel/blob/affcfac39bf479a9ac64dcb41e7650d0f8...)
to get from a linked list hook to a map iterator.
Maintenance:
It seems important to follow what is going on in the standard. I see you
already have is_transparent, the node stuff, that's good. You are missing
at least erase_if though.
Thank you for maintaining this Boost library,
--
Marc Glisse
