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perf(hashing): Much faster hash algorithm

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For compositions we have implimented a much faster hashing algorithm
This commit is contained in:
Emily Boudreaux
2025-12-07 09:41:58 -05:00
parent 3dc697dd6e
commit 184df676ca
9 changed files with 219 additions and 168 deletions
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57
tests/composition/compositionTest.cpp
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@@ -367,43 +367,6 @@ TEST_F(compositionTest, negativeZeroEqualsPositiveZero) {
fourdst::composition::utils::CompositionHash::hash_exact(b));
}
TEST_F(compositionTest, quantizedIgnoresTinyJitter) {
fourdst::composition::Composition a, b;
a.registerSymbol("H-1"); b.registerSymbol("H-1");
a.setMolarAbundance("H-1", 1.0);
b.setMolarAbundance("H-1", 1.0 + 5e-14); // smaller than eps
const double eps = 1e-12;
const auto hqa = fourdst::composition::utils::CompositionHash::hash_quantized(a, eps);
const auto hqb = fourdst::composition::utils::CompositionHash::hash_quantized(b, eps);
ASSERT_EQ(hqa, hqb);
// But exact should differ if the bit pattern changes
const auto hea = fourdst::composition::utils::CompositionHash::hash_exact(a);
const auto heb = fourdst::composition::utils::CompositionHash::hash_exact(b);
ASSERT_NE(hea, heb);
}
TEST_F(compositionTest, quantizedDetectsAboveEps) {
fourdst::composition::Composition a, b;
a.registerSymbol("H-1"); b.registerSymbol("H-1");
a.setMolarAbundance("H-1", 1.0);
b.setMolarAbundance("H-1", 1.0 + 2e-12); // larger than eps
const double eps = 1e-12;
ASSERT_NE(fourdst::composition::utils::CompositionHash::hash_quantized(a, eps),
fourdst::composition::utils::CompositionHash::hash_quantized(b, eps));
}
TEST_F(compositionTest, exactVsQuantizedDifferentSeeds) {
fourdst::composition::Composition a;
a.registerSymbol("H-1"); a.setMolarAbundance("H-1", 0.5);
const auto he = fourdst::composition::utils::CompositionHash::hash_exact(a);
const auto hq = fourdst::composition::utils::CompositionHash::hash_quantized(a, 1e-12);
ASSERT_NE(he, hq);
}
TEST_F(compositionTest, cloneAndCopyStable) {
std::vector<std::string> symbols = {"H-1", "He-4"};
std::vector<double> abundances = {0.6, 0.4};
@@ -442,15 +405,12 @@ TEST_F(compositionTest, canonicalizeNaNIfAllowed) {
}
TEST_F(compositionTest, hash) {
using namespace fourdst::atomic;
fourdst::composition::Composition a, b;
a.registerSymbol("H-1"); b.registerSymbol("H-1");
a.setMolarAbundance("H-1", 0.6); b.setMolarAbundance("H-1", 0.6);
EXPECT_NO_THROW((void)a.hash());
EXPECT_EQ(a.hash(), b.hash());
}
TEST_F(compositionTest, hashCaching) {
using namespace fourdst::atomic;
const std::unordered_map<Species, double> abundances ={
{H_1, 0.702},
{He_4, 0.06},
@@ -458,19 +418,8 @@ TEST_F(compositionTest, hashCaching) {
{N_14, 0.0005},
{O_16, 0.22},
};
const fourdst::composition::Composition a(abundances);
const auto first_hash_clock_start = std::chrono::high_resolution_clock::now();
(void)a.hash();
const auto first_hash_clock_end = std::chrono::high_resolution_clock::now();
const auto first_hash_duration = std::chrono::duration_cast<std::chrono::nanoseconds>(first_hash_clock_end - first_hash_clock_start).count();
const auto second_hash_clock_start = std::chrono::high_resolution_clock::now();
(void)a.hash();
const auto second_hash_clock_end = std::chrono::high_resolution_clock::now();
const auto second_hash_duration = std::chrono::duration_cast<std::chrono::nanoseconds>(second_hash_clock_end - second_hash_clock_start).count();
EXPECT_LT(second_hash_duration, first_hash_duration);
fourdst::composition::Composition c(abundances), d(abundances);
EXPECT_EQ(c.hash(), d.hash());
}
TEST_F(compositionTest, hashStaleing) {