Note the command to generate a seed for util::make_hash

Author: yut23

2023/src/day16.hpp

@@ -159,7 +159,7 @@ template <>
 struct std::hash<aoc::day16::GraphHelper_Key> {
     std::size_t
     operator()(const aoc::day16::GraphHelper_Key &key) const noexcept {
-        // random number
+        // random number (hexdump -n8 -e '"0x" 8/1 "%02x" "ull\n"'</dev/urandom)
         std::size_t seed = 0x57456df670c76ed8ull;
         util::make_hash(seed, key.pos.x, key.pos.y, key.dir);
         return seed;

2023/src/day17.hpp

@@ -213,7 +213,7 @@ CityMap CityMap::read(std::istream &is) {
 template <>
 struct std::hash<aoc::day17::CityMap::Key> {
     std::size_t operator()(const aoc::day17::CityMap::Key &key) const noexcept {
-        // random number
+        // random number (hexdump -n8 -e '"0x" 8/1 "%02x" "ull\n"'</dev/urandom)
         std::size_t seed = 0x580ac2097baf0cb7ull;
         util::make_hash(seed, key.pos.x, key.pos.y,
                         key.orient == aoc::day17::Orientation::horizontal);

aoc_lib/src/lib.hpp

@@ -495,7 +495,7 @@ template <std::integral int_type>
 struct std::hash<aoc::GenericPos<int_type>> {
     std::size_t
     operator()(const aoc::GenericPos<int_type> &pos) const noexcept {
-        // random number
+        // random number (hexdump -n8 -e '"0x" 8/1 "%02x" "ull\n"'</dev/urandom)
         std::size_t seed = 0xbedb5bb0b473b6b7ull;
         util::make_hash(seed, pos.x, pos.y);
         return seed;

aoc_lib/src/util/hash.hpp

@@ -44,6 +44,9 @@ void murmurhash2_finalize(std::size_t &h) {
     h ^= h >> r;
 }
 
+/**
+ * Generate a seed with `hexdump -n8 -e '"0x" 8/1 "%02x" "ull\n"' </dev/urandom`
+ */
 template <util::concepts::Hashable... Ts>
 void make_hash(std::size_t &seed, const Ts... components) {
     (hash::murmurhash2_combine(seed, std::hash<Ts>{}(components)), ...);