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Tool for instantiating a C++ template at runtime? in c/[email protected]
[–] [email protected] 1 points 9 months ago

Personally I think child processes are the right approach for this. Launch a new process* for each query and it can (if you choose to go that route) dynamically load in compiled code. Exit when you’re done, and the dynamically loaded code is gone. A side benefit of that is memory leaks are contained, since all memory you allocate is about to be removed anyway.

I'd probably be fine with hundreds or thousands of these hanging in memory. I suspect the generated code for a single query would be in hundreds of kilobytes, maybe a megabyte. But yeah, this is one of those technical details I'd worry about.

Honestly, I wonder if you could just use an actual HTTP server for this? They can handle hundreds or even thousands of simultaneous requests. They can handle requests that complete in a fraction of a millisecond or ones that run for several hours. And they have good tools to catch/deal with code that segfaults, hits an endless loop, attempts to allocate terabytes of swap, etc. HTTP also has wonderful tools to load balance across multiple servers if you do need to scale to massive numbers of requests.

Not sure how a HTTP server would solve the CPU bottleneck of scanning terabytes of data per query?

Tool for instantiating a C++ template at runtime? in c/[email protected]
[–] [email protected] 2 points 9 months ago

I somehow didn't think a regular JIT solution might be applicable here, but it is. Thank you! There seems to be a number of projects doing JIT for C++, will look at them.

19
Tool for instantiating a C++ template at runtime? (lemm.ee)
 

I'm working on a query engine, essentially a tool to scan/filter/annotate by lookups/group by/aggregate a large dataset, tens-of-terabytes range. The compute part seems to be a bottleneck for me (I'll be doing around 80-300 GB/s of reads, and yes, I will have hardware capable of providing that kind of throughput). My hypothesis is that by encoding query in form of template arguments I can make the compiler generate code optimized for a specific type of query (like, the filtering or aggregation keys). But I do not know what queries will users send, so I need a way to instantiate templates at runtime.

Sounds simple: for a new type of query invoke a compiler at runtime to build a dynamic library with a new instantiation, then dynload it and off we go. Some prior work is here, though I'm pretty sure any JIT compiler also can counts here. But there's enough technical details to worry about, and at the same time this idea isn't novel, so I wonder—are there any packaged solutions for this kind of approach?

0
C++ Design Patterns for Low-latency Applications Including High-frequency Trading (arxiv.org)
 

While high-frequency trading is not exactly my favourite topic, I do like reading on their technical approaches.

By Paul Bilokon, Burak Gunduz

This work aims to bridge the existing knowledge gap in the optimisation of latency-critical code, specifically focusing on high-frequency trading (HFT) systems. The research culminates in three main contributions: the creation of a Low-Latency Programming Repository, the optimisation of a market-neutral statistical arbitrage pairs trading strategy, and the implementation of the Disruptor pattern in C++. The repository serves as a practical guide and is enriched with rigorous statistical benchmarking, while the trading strategy optimisation led to substantial improvements in speed and profitability. The Disruptor pattern showcased significant performance enhancement over traditional queuing methods. Evaluation metrics include speed, cache utilisation, and statistical significance, among others. Techniques like Cache Warming and Constexpr showed the most significant gains in latency reduction. Future directions involve expanding the repository, testing the optimised trading algorithm in a live trading environment, and integrating the Disruptor pattern with the trading algorithm for comprehensive system benchmarking. The work is oriented towards academics and industry practitioners seeking to improve performance in latency-sensitive applications.

Linux file system developer: we're severely under-resourced in c/[email protected]
[–] [email protected] 1 points 1 year ago

This plea for help is specifically for non-coding, but still deeply technical work.

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Linux file system developer: we're severely under-resourced (lore.kernel.org)
 

I've said this previously, and I'll say it again: we're severely under-resourced. Not just XFS, the whole fsdevel community. As a developer and later a maintainer, I've learnt the hard way that there is a very large amount of non-coding work is necessary to build a good filesystem. There's enough not-really-coding work for several people. Instead, we lean hard on maintainers to do all that work. That might've worked acceptably for the first 20 years, but it doesn't now.

[…]

Dave and I are both burned out. I'm not sure Dave ever got past the 2017 burnout that lead to his resignation. Remarkably, he's still around. Is this (extended burnout) where I want to be in 2024? 2030? Hell no.

How does everyone feel about Motorola phones? in c/[email protected]
[–] [email protected] 1 points 1 year ago* (last edited 1 year ago)

I'm not a person who'd be loyal to a brand. Yet Motorola consistently produces devices that turn out to be the best trade-offs (price to functionality) for me. And, so far, all these devices were pretty durable as well, though it's not that I really put smartphones into lots of use. That's all I can say.