On 14:15 Mon 24 Aug , Niall Douglas wrote:
On 24 Aug 2015 at 7:37, Andreas Schäfer wrote:
In "Complexity guarantees" some of the minimum complexities exceed their maximum counterparts (e.g. "51 opcodes <= Value transport <= 32 opcodes"). What's that supposed to mean? What is the rationale behind citing minimum complexities? And why do you measure opcodes instead of, say, time?
Monad is designed to be as absolutely as lightweight as possible, and is per-commit CI tested to ensure it generates no more than X opcodes per operation.
Traditional complexities such as O(N) make no sense for Monad. No operation it does isn't constant time. You're really testing how friendly Monad is to the compiler optimiser (which is very friendly).
OK, but how is the number of opcodes relevant in any practical setting? I for one expect the compiler to generate fast code. And if that means that one horribly slow instruction gets replaces by 10 fast ones, then so be it. I'd suggest to set up performance tests which measure time or throughput for sets of typical workloads. I'm still unsure what "51 opcodes <= Value transport <= 32 opcodes" is supposed to mean.
Since you mentioned monads were basically identical: why don't you just use std::future?
AFIO has never been able to return a plain std::future because of the lack of standardised wait composure in current C++ i.e. when_all(futures ...). It returns an afio::future<> which internally keeps a unique integer which looks up stored continuations in an unordered_map. This let AFIO implement continuations on top of std::future.
OK, this explains why you're using afio::future instead of std::future, but not why afio::future relies on afio::monad instead of std::future. AFAICS basic_monad doesn't add much over future's API, except for get_or() and friends. But those functions aren't being used anyway, right?
Monad contains a full Concurrency TS implementation, and works everywhere in any configuration and currently with far lower overheads than any existing STL implementation by a big margin (about 50%).
That's a big claim. Do you have performance tests to back it up? Which which implementation did you compare your results?
That means AFIO can drop the internal unordered_map, and become a pure Concurrency TS implementation with no workarounds and more importantly, no central locking at all. That will eliminate the last remaining synchronisation in AFIO, and it will be a pure wait free solution.
So, is AFIO composable with other parallel code? Could I use it along with other threads? Thanks! -Andreas -- ========================================================== Andreas Schäfer HPC and Grid Computing Department of Computer Science 3 Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany +49 9131 85-27910 PGP/GPG key via keyserver http://www.libgeodecomp.org ========================================================== (\___/) (+'.'+) (")_(") This is Bunny. Copy and paste Bunny into your signature to help him gain world domination!