hash_vector.cpp

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// Copyright (c) 2021, Aalto University, developed by Erik Schultheis
// All rights reserved.
//
// SPDX-License-Identifier: MIT
 
#include "hash_vector.h"
#include <atomic>
 
using namespace dismec;
 
namespace {
    std::size_t get_next_id()
    {
        static std::atomic<std::size_t> next_id{0};
        static_assert(sizeof(std::size_t) >= 8, "std::size_t is expected to be at least 64 bit, so that we can be sure our unique ids never wrap around.");
 
        // see also https://stackoverflow.com/questions/41206861/atomic-increment-and-return-counter
        return next_id++;
    }
 
}
 
HashVector::HashVector(DenseRealVector data) :
    m_UniqueID(get_next_id()),
    m_Data(std::move(data)) {
}
 
void HashVector::update_id() {
    m_UniqueID = get_next_id();
}
 
VectorHash HashVector::hash() const {
    return {m_UniqueID};
}
 
VectorHash::VectorHash() : m_UniqueID(-1) {
}
 
#include "doctest.h"
 
TEST_CASE("HashVector content") {
    HashVector hv(DenseRealVector::Zero(3));
 
    CHECK(hv->coeff(0) == 0.0);
    CHECK(hv->coeff(1) == 0.0);
    CHECK(hv->coeff(2) == 0.0);
 
    hv = DenseRealVector::Ones(3);
    CHECK(hv->coeff(0) == 1.0);
    CHECK(hv->coeff(1) == 1.0);
    CHECK(hv->coeff(2) == 1.0);
}
 
TEST_CASE("HashVector versioning") {
    VectorHash vh;
    HashVector hv(DenseRealVector::Zero(3));
 
    CHECK(vh != hv.hash());
    vh = hv.hash();
    CHECK(vh == hv.hash());
 
    // non-mutating operation
    auto content = hv.get();
    content = hv + DenseRealVector::Ones(3);
    CHECK(vh == hv.hash());
    CHECK(hv->coeff(0) == 0.0);
 
    hv = DenseRealVector::Ones(3);
    CHECK(vh != hv.hash());
}
 
TEST_CASE("HashVector uniqueness") {
    HashVector hv(DenseRealVector::Zero(3));
    HashVector hw(DenseRealVector::Zero(3));
 
    CHECK( hv.hash() != hw.hash() );
}
 
TEST_CASE("uninitialized VectorHash") {
    VectorHash vh;
 
    HashVector hv(DenseRealVector::Zero(3));
    CHECK_FALSE(vh == hv.hash());
    CHECK_FALSE(hv.hash() == vh);
}