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Flux-openbuild/test/test_inverse.cpp
2025-10-06 20:21:40 +00:00

141 lines
4.6 KiB
C++

#include "test_common.h"
#include "./utils/matrix.h"
#include "./utils/vector.h"
#include "./numerics/inverse.h"
#include "./numerics/matmul.h"
// ---------- helpers ----------
template <typename T>
static utils::Matrix<T> identity(std::uint64_t n) {
utils::Matrix<T> I(n,n,T(0));
for (std::uint64_t i=0;i<n;++i) I(i,i) = T(1);
return I;
}
template <typename T>
static bool mats_equal_tol(const utils::Matrix<T>& X,
const utils::Matrix<T>& Y,
double tol = 1e-12) {
if (X.rows()!=Y.rows() || X.cols()!=Y.cols()) return false;
for (std::uint64_t i=0;i<X.rows();++i)
for (std::uint64_t j=0;j<X.cols();++j)
if (std::fabs(double(X(i,j) - Y(i,j))) > tol) return false;
return true;
}
// A small well-conditioned SPD 3x3
static utils::Matrix<double> make_A3() {
utils::Matrix<double> A(3,3,0.0);
// [ 4 3 0
// 3 4 -1
// 0 -1 4 ]
A(0,0)=4; A(0,1)=3; A(0,2)=0;
A(1,0)=3; A(1,1)=4; A(1,2)=-1;
A(2,0)=0; A(2,1)=-1; A(2,2)=4;
return A;
}
// A random-ish SPD 5x5 (constructed deterministically)
static utils::Matrix<double> make_A5_spd() {
utils::Matrix<double> R(5,5,0.0);
// Fill R with a simple pattern
double v=1.0;
for (std::uint64_t i=0;i<5;++i)
for (std::uint64_t j=0;j<5;++j, v+=0.37)
R(i,j) = std::fmod(v, 3.0) - 1.0; // values in [-1,2)
// A = R^T R + 5 I → SPD and well-conditioned
utils::Matrix<double> Rt(5,5,0.0);
for (std::uint64_t i=0;i<5;++i)
for (std::uint64_t j=0;j<5;++j)
Rt(i,j) = R(j,i);
auto RtR = numerics::matmul(Rt, R);
for (std::uint64_t i=0;i<5;++i) RtR(i,i) += 5.0;
return RtR;
}
// ---------- tests ----------
TEST_CASE(Inverse_GJ_3x3) {
auto A = make_A3();
auto A_copy = A;
auto Inv = numerics::inverse(A, "Gauss-Jordan"); // non-inplace
auto I = identity<double>(3);
auto AInv = numerics::matmul(A, Inv);
auto InvA = numerics::matmul(Inv, A);
CHECK(mats_equal_tol(AInv, I, 1e-11), "A*Inv != I (Gauss-Jordan)");
CHECK(mats_equal_tol(InvA, I, 1e-11), "Inv*A != I (Gauss-Jordan)");
// A should be unchanged by numerics::inverse (it copies internally)
CHECK(mats_equal_tol(A, A_copy, 1e-15), "inverse() modified input A");
}
TEST_CASE(Inverse_LU_3x3) {
auto A = make_A3();
auto Inv = numerics::inverse(A, "LU");
auto I = identity<double>(3);
auto AInv = numerics::matmul(A, Inv);
auto InvA = numerics::matmul(Inv, A);
CHECK(mats_equal_tol(AInv, I, 1e-11), "A*Inv != I (LU)");
CHECK(mats_equal_tol(InvA, I, 1e-11), "Inv*A != I (LU)");
}
TEST_CASE(Inplace_Inverse_Both_Methods_Agree_5x5) {
auto A = make_A5_spd();
auto GJ = A; numerics::inplace_inverse(GJ, "Gauss-Jordan");
auto LU = A; numerics::inplace_inverse(LU, "LU");
// Both should be valid inverses
auto I = identity<double>(5);
CHECK(mats_equal_tol(numerics::matmul(A, GJ), I, 1e-10), "A*GJ != I");
CHECK(mats_equal_tol(numerics::matmul(GJ, A), I, 1e-10), "GJ*A != I");
CHECK(mats_equal_tol(numerics::matmul(A, LU), I, 1e-10), "A*LU != I");
CHECK(mats_equal_tol(numerics::matmul(LU, A), I, 1e-10), "LU*A != I");
// And they should be very close to each other
CHECK(mats_equal_tol(GJ, LU, 1e-10), "Gauss-Jordan inverse != LU inverse");
}
TEST_CASE(Inverse_NonSquare_Throws) {
utils::Matrix<double> A(2,3,1.0);
bool threw=false;
try { auto B = numerics::inverse(A, "Gauss-Jordan"); (void)B; } catch(const std::runtime_error&) { threw=true; }
CHECK(threw, "inverse should throw on non-square (Gauss-Jordan)");
threw=false;
try { numerics::inplace_inverse(A, "LU"); } catch(const std::runtime_error&) { threw=true; }
CHECK(threw, "inplace_inverse should throw on non-square (LU)");
}
TEST_CASE(Inverse_Singular_Throws) {
utils::Matrix<double> A(3,3,0.0);
// Two identical rows → singular
A(0,0)=1; A(0,1)=2; A(0,2)=3;
A(1,0)=1; A(1,1)=2; A(1,2)=3;
A(2,0)=0; A(2,1)=1; A(2,2)=4;
bool threw=false;
try { auto B = numerics::inverse(A, "Gauss-Jordan"); (void)B; } catch(const std::runtime_error&) { threw=true; }
CHECK(threw, "inverse(GJ) should throw on singular");
threw=false;
try { auto B = numerics::inverse(A, "LU"); (void)B; } catch(const std::runtime_error&) { threw=true; }
CHECK(threw, "inverse(LU) should throw on singular");
}
TEST_CASE(Inverse_Invalid_Method_Throws) {
auto A = make_A3();
bool threw=false;
try { auto B = numerics::inverse(A, "NotAThing"); (void)B; } catch(const std::runtime_error&) { threw=true; }
CHECK(threw, "inverse should throw on unknown method");
}