Are there packages that implement alternatives to Base.hash? I am interested in a somewhat different set of tradeoffs than what Base.hash provides: Should be able to hash any object (like Base.hash) Should have a negligible probability to produce collisions (unlike Base.hash). Can be slower than B…

You’re free to implement Base.hash on your own type, to avoid the fallback to objectid: help?> hash search: hash hasmethod haskey hasfield hasproperty skipchars Threads hash(x[, h::UInt]) -> UInt Compute an integer hash code such that isequal(x,y) implies hash(x)==hash(y). The optional seco…

Also of interest are probably https://github.com/JuliaLang/julia/issues/40717 and https://github.com/JuliaLang/julia/issues/4648

see also [image] Stable hashing across Julia versions General Usage If the values are always arrays of ints or something comparable, then you could just use write to get a “canonical” binary representation and use CRC32 or SHA to hash that binary data. If the data is more …

Thanks @Sukera for the quick replies. You’re free to implement Base.hash on your own type, to avoid the fallback to objectid This works only for types I “own” for other types this is piracy. Why do you think Base.hash is likely to produce collision? Because it does not even depend on all the…

Thanks, it is a workaround, but it has some issues: Calculating a hash then requires writing and reading from disk The hash is only as stable as the serialization mechanism

SHA and variants are only defined for String (or equivalently, Vector{UInt8}. The hard part isn’t a good hashing algorithm, it’s expanding it to be able to hash anything.

Yes so I think there are three things that need to be done: Given a blob of contiguous bytes, provide a hash. This can be done with SHA etc Given hashes of the fields of an object and the hash of its type mix it into a single hash Produce a hash of a type I think for 1. and 2. there exist lots of…

[image] jw3126: Given a blob of contiguous bytes, provide a hash. This can be done with SHA etc Given hashes of the fields of an object and the hash of its type mix it into a single hash Produce a hash of a type @haberdashPI wrote a package StableHashTraits.jl that does some of this. It’s no…

Sounds awesome, looking forward to trying it out.

[image] jw3126: Because it does not even depend on all the input bits: N = 10^5 x1 = randn(N) x2 = copy(x1) x2[10000] = 0 @assert hash(x1) == hash(x2) Ok, reading through @edit hash(x1) yeah it doesn’t take all elements into account for performance reasons. Seems like that code is 4+ years o…

Alternatives to `Base.hash`?

General Usage

MarcMush April 7, 2022, 12:15pm 4

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Persistent hash of julia object General Usage	12	3240	January 20, 2017
Overloading Base.hash is 2x slower than an identical function Performance	1	372	June 17, 2021
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Fast hash for custom type General Usage question , performance , hash	10	971	September 17, 2021
Stable hashing across Julia versions General Usage	7	1398	September 23, 2020

Alternatives to `Base.hash`?

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