abseil-cpp VS Bazel

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.

Wow, if you curl it, there's a lot of boilerplate code there.

Maybe built using Bazel?

https://bazel.build

Bazel by Google

Luckily a feature to limit the disk cache size is in development: https://github.com/bazelbuild/bazel/issues/5139

This is a problem that Bazel (https://bazel.build) solves in a very convenient way. You can just keep using the paths relative to the repository root, and as long as you properly declare your test needs that file it will access it without problems. Or you can use the runfile libraries to access them too.

When doing research for this lab exercise I looked at both vcpkg and conan. Both are package managers that would automate the installation and configuration of my program with its dependencies. However, when it came to releasing and sharing my program my options were limited. For example, the central public registry for conan packages is conan-center, but these packages are curated and the process is very involved. There was no way conan-center would accept a class project like mine. Alternatively, I could host a conan package on a public Artifactory repository, but accessing the package requires users to add the repository to their conan remote. This already sounded like too many steps to expect regular users to follow - I already haven't setup any conan remotes, there's no way I could expect regular users to know about conan remotes, let alone have conan installed on their system. After discussing with people online and consulting my instructor, I ultimately decided to do a GitHub release. However, in the future I was encouraged to look into using CMake or bazel.

NOTE: I won’t mention SBT and Leiningen here because, with all due respect, they are niche build tools. I also won’t discuss Kobalt for the same reason (besides, it’s no longer actively maintained). Additionally, I won’t touch upon Bazel and Buck in this context, mainly because I’m not very familiar with them. If you have insights or comments about these tools, please feel free to share them in the comments 👇

> None of this solves C's only REAL problem (in my opinion) which is the lack of dependency management.

Bazel solves this really nicely, I know some people have strong opinions on it but I cannot recommend it enough

https://bazel.build/