performance

Most efficient way to map function over numpy array

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I’ve tested all suggested methods plus np.array(list(map(f, x))) with perfplot (a small project of mine). Message #1: If you can use numpy’s native functions, do that. If the function you’re trying to vectorize already is vectorized (like the x**2 example in the original post), using that is much faster than anything else (note the log … Read more

Why does C++ compilation take so long?

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Several reasons Header files Every single compilation unit requires hundreds or even thousands of headers to be (1) loaded and (2) compiled. Every one of them typically has to be recompiled for every compilation unit, because the preprocessor ensures that the result of compiling a header might vary between every compilation unit. (A macro may … Read more

Which is faster: while(1) or while(2)?

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Both loops are infinite, but we can see which one takes more instructions/resources per iteration. Using gcc, I compiled the two following programs to assembly at varying levels of optimization: int main(void) { while(1) {} return 0; } int main(void) { while(2) {} return 0; } Even with no optimizations (-O0), the generated assembly was … Read more

Performance optimization strategies of last resort [closed]

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OK, you’re defining the problem to where it would seem there is not much room for improvement. That is fairly rare, in my experience. I tried to explain this in a Dr. Dobbs article in November 1993, by starting from a conventionally well-designed non-trivial program with no obvious waste and taking it through a series … Read more

Preferred method to store PHP arrays (json_encode vs serialize)

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Depends on your priorities. If performance is your absolute driving characteristic, then by all means use the fastest one. Just make sure you have a full understanding of the differences before you make a choice Unlike serialize() you need to add extra parameter to keep UTF-8 characters untouched: json_encode($array, JSON_UNESCAPED_UNICODE) (otherwise it converts UTF-8 characters … Read more

When to use CouchDB over MongoDB and vice versa

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Of C, A & P (Consistency, Availability & Partition tolerance) which 2 are more important to you? Quick reference, the Visual Guide To NoSQL Systems MongodB : Consistency and Partition Tolerance CouchDB : Availability and Partition Tolerance A blog post, Cassandra vs MongoDB vs CouchDB vs Redis vs Riak vs HBase vs Membase vs Neo4j … Read more

Which method performs better: .Any() vs .Count() > 0?

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If you are starting with something that has a .Length or .Count (such as ICollection<T>, IList<T>, List<T>, etc) – then this will be the fastest option, since it doesn’t need to go through the GetEnumerator()/MoveNext()/Dispose() sequence required by Any() to check for a non-empty IEnumerable<T> sequence. For just IEnumerable<T>, then Any() will generally be quicker, … Read more

What is the runtime performance cost of a Docker container?

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An excellent 2014 IBM research paper “An Updated Performance Comparison of Virtual Machines and Linux Containers” by Felter et al. provides a comparison between bare metal, KVM, and Docker containers. The general result is: Docker is nearly identical to native performance and faster than KVM in every category. The exception to this is Docker’s NAT — if you … Read more