It's trivial to force a collision. Here's the same UUID twice:
6e197264-d14b-44df-af98-39aac5681791
6e197264-d14b-44df-af98-39aac5681791
Typically, you don't care about UUIDs that aren't in your system and you generate those yourself to avoid maliciously generated collisions. Your system can't handle 2^61 IDs. It doesn't have the processing power, storage, or bandwidth for that to happen. Not to mention traditional rate limiting.
>2^61 is still a very large number of course, but much more feasible to reach than 2^122 when doing a collision attack. This is the reason that cryptographic hashes are typically 256 bits or more (to make the cost of collision attacks >= 2^128).
So assuming you use 64-bit counters, you can divide those 12 years by 1024 to get 4 days.
And that's not even considering what you could do on a GPU.
Edit: I might be off by a factor of 2, not sure if the SIMD throughput is per-core or per-thread. Also thermal throttling. Same ballpark though!
Then your 32 HT threads aren’t really going to give you full access to the underlying SIMD registers which are going to be per core which is where I assume you realized the 2x difference might show up?
And to do += 1 multithreaded you have to partition the range or you won’t get any speed up - if you don’t amortize the cost of atomic synchronization across threads you’re going to be going slower than a non-SIMD increment.
