Boost VS abseil-cpp

git clone https://github.com/boostorg/boost.git -b ${{ inputs.branch }} "${{ inputs.boost-dir }}" --depth 1 git submodule update --depth 1 -q --init tools/boostdep python tools/boostdep/depinst/depinst.py --include library_i_want"

Any thoughts on why it has exactly the same name as a popular source available project that's been around since the 1990s?

earliest archive: https://web.archive.org/web/19991011120524/http://www.boost....

latest commit (today): https://github.com/boostorg/boost/commit/7727baea944c6365301...

naming in 2023: "The Boost project provides free peer-reviewed portable C++ source libraries"

naming in 1999: "The Boost web site provides a repository for free C++ libraries"

Hmm...

include(FetchContent) FetchContent_Declare(boost URL https://github.com/boostorg/boost/releases/download/boost-1.81.0/boost-1.81.0.tar.xz ) FetchContent_MakeAvailable(boost) ...

set(BOOST_INCLUDE_LIBRARIES system thread) # enabled libraries set(BOOST_ENABLE_CMAKE ON) # CMake support FetchContent_Declare(boost GIT_REPOSITORY https://github.com/boostorg/boost.git ...

In fact, boost has cmake files now — pretty recent addition and I haven’t got around to testing, but no reason to think it doesn’t work. https://github.com/boostorg/boost. Also, boost is getting more modular with every release — more and more libraries can be pulled independently with mostly only depending on boost.core. Asio has been like this forever, but Boost.math is a recent example to the bandwagon. You can find an independent release package for math on GitHub now.

Do you build boost from sources? If so, maybe get the tar balls from their Github repository?

Yeah, it's nice! And Abseil does it, IFF you use LLVM libc++.

https://github.com/abseil/abseil-cpp/blob/master/absl/string...

The standard adopted it as resize_and_overwrite. Which I think is a little clunky.

This may be confusing to those familiar with Google's libraries. The baseline is the Go BTree, which I personally never heard of until just now, not the C++ absl::btree_set. The benchmarks aren't directly comparable, but the C++ version also comes with good microbenchmark coverage.

https://github.com/google/btree

https://github.com/abseil/abseil-cpp/blob/master/absl/contai...

An implementation of call_once that accommodates callbacks that throw: https://github.com/abseil/abseil-cpp/blob/master/absl/base/c...

I wouldn't say it's that cryptic. It's just a few bitwise rotations/shifts/xor operations.

You can see hashing optimizations as well https://www.deepmind.com/blog/alphadev-discovers-faster-sort..., https://github.com/abseil/abseil-cpp/commit/74eee2aff683cc7d...

I was one of the members who reviewed expertly what has been done both in sorting and hashing. Overall it's more about assembly, finding missed compiler optimizations and balancing between correctness and distribution (in hashing in particular).

It was not revolutionary in a sense it hasn't found completely new approaches but converged to something incomprehensible for humans but relatively good for performance which proves the point that optimal programs are very inhuman.

Note that for instructions in sorting, removing them does not always lead to better performance, for example, instructions can run in parallel and the effect can be less profound. Benchmarks can lie and compiler could do something differently when recompiling the sort3 function which was changed. There was some evidence that the effect can come from the other side.

For hashing it was even funnier, very small strings up to 64 bit already used 3 instructions like add some constant -> multiply 64x64 -> xor upper/lower. For bigger ones the question becomes more complicated, that's why 9-16 was a better spot and it simplified from 2 multiplications to just one and a rotation. Distribution on real workloads was good, it almost passed smhasher and we decided it was good enough to try out in prod. We did not rollback as you can see from abseil :)

But even given all that, it was fascinating to watch how this system was searching and was able to find particular programs can be further simplified. Kudos to everyone involved, it's a great incremental change that can bring more results in the future.

Check out https://abseil.io. It offers absl::optional, which is a backport of std::optional.