The article explains modulo bias — a common but subtle bug when using the modulo operator to constrain random numbers to a range, which breaks the uniform distribution. Using a uniform u64 random and taking modulo 10 for a set of 10 items means some items are slightly more likely to be chosen than others, since 2^64 is not evenly divisible by 10.
Background
Modulo bias is a well-known issue in programming that affects anyone generating random selections from a set whose size doesn't divide evenly into the random number generator's output range.
- Source
- Lobsters
- Published
- Oct 7, 2026 at 08:43 AM
- Score
- 6.0 / 10