Yes, I meant map[uint64][]struct{K;V}, thanks for correcting me.
On Wed, 25 Jun 2025 at 20:06, robert engels <reng...@ix.netcom.com> wrote:
> That is not correct and will not work - what the op is talking about is if
> K collides - so this is only a single K - so map[K][]struct{K;V} will only
> ever have one element in the array…
>
> On Jun 25, 2025, at 12:33 PM, 'Axel Wagner' via golang-nuts <
> golang-nuts@googlegroups.com> wrote:
>
> There are ∞ many possible hashable Go values (in particular, all strings)
> and 2^64 uint64, so yes, there is a possibility of collision.
> How big that risk is depends on how many values you have and what the
> damage is, if a collision happens.
> Wikipedia has a nifty table:
> https://en.wikipedia.org/wiki/Birthday_attack#Mathematics
> There, you can see that if you have a 64 bit hash and have, say 190K
> elements, the probability of a random collision is roughly 10^-9 (so pretty
> small, but not completely impossible).
> If a collision is truly problematic, a simple fix would be to use a
> map[K][]struct{K;V}. That way, if there *is* a collision on the hash, you
> store all the colliding values and can walk the slice to find the right
> one. As collisions should be rare, that should be an uncommon cost to pay.
>
> On Wed, 25 Jun 2025 at 17:26, Pierre Durand <pierredur...@gmail.com>
> wrote:
>
>> Is it safe to use the result of a hash/maphash (uint64) as a map key.
>> Is there a risk of collision ? (different inputs generate the same hash)
>>
>> Thank you
>>
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