[pbs-devel] applied: [PATCH proxmox-backup] docs: fix hash collision probability comparison

[Dominik Csapak]

On 3/7/25 11:27, Thomas Lamprecht wrote:
> On 07/03/2025 10:33, Dominik Csapak wrote:
>> Commit:
>>   efc09f63c (docs: tech overview: avoid 'we' and other small style fixes/additions)
>>
>> introduced the comparison with 13 lottery games, but sadly without any
>> mention how to arrive at that number.
>>
>> When calculating I did arrive at 8-9 games (8 is more probable, 9 is
>> less probable), so rewrite to 'chance is lower than 8 lottery games' and
>> give the calculation directly inline as a reference.
>>
>> Suggested-by: Dietmar Maurer <dietmar at proxmox.com>
>> Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
>> ---
>> @Thomas: if you can remember how we arrived at the '13' all those years
>> ago, we could check if that calculation makes more sense than what I'm
>> doing here, and rererence it?
> 
> I remember that we discussed this a bit, but cannot  come up with anything
> that'd would explain this number, as it seems rather obviously wrong.
> My commit introducing this is also _far_ from ideal, so the mistake might
> not even be directly in having chosen number, but possibly an oversight and
> including some unfinished addition to the docs with a cleanup commit.
> 
> 
> Anyhow, rechecked the math now and winning 8 lotto game of 6 out of 45 in
> a row checks out, as:
> 
> (1 / binomial(45, 6))^8 ≈ 5.162329215E-56 << 3.1115E-61
> 
> and
> 
> (1 / binomial(45, 6))^9 ≈ 6.337987952E-63 >> 3.1115E-61
> 
> 
> btw. liking `qalc`, a calculator with a good REPL CLI interface, more and
> more, much more ergonomical than bc or the like but still lightweight and
> tuned for math – unlike using a REPL of a interpreter like perl or python.
> 

nice, have to look at this in the future. Currently, when doing calculations
with such big numbers, i still use wolframalpha.

>>
>>   docs/technical-overview.rst | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>>
> 
> applied, thanks!