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Fix table size calculation and documentation for 10% waste

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Co-authored-by: jll63 <5083077+jll63@users.noreply.github.com>
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copilot-swe-agent[bot]
2025-12-18 05:35:01 +00:00
parent 7e44f683ea
commit d2885bad94
1 changed files with 3 additions and 5 deletions
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8
include/boost/openmethod/policies/minimal_perfect_hash.hpp
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@@ -49,7 +49,7 @@ namespace policies {
//! determine values for `M` and `N` that result in a minimal perfect hash
//! function for the set of registered type_ids. This means that the hash
//! function is collision-free and the codomain is approximately the size of
//! the domain, resulting in a dense range [0, n-1] for n inputs.
//! the domain, resulting in a dense range [0, 1.1*n-1] for n inputs.
//!
//! Unlike @ref fast_perfect_hash, which uses a hash table of size 2^k
//! (typically larger than needed) and may have unused slots, this policy
@@ -194,10 +194,8 @@ void minimal_perfect_hash::fn<Registry>::initialize(
}
// Table size is N * 1.1 to allow up to 10% waste (makes finding hash easier)
table_size = N + N / 10;
if (table_size == N && N > 0) {
table_size = N + 1; // Ensure at least 1 extra slot for N > 0
}
// Use (N * 11 + 9) / 10 to ensure proper rounding up for small N
table_size = (N * 11 + 9) / 10;
if (table_size == 0) {
shift = 0;