Small refactor of SVD implimentation

This commit is contained in:
2026-08-14 11:02:25 -04:00
parent 5600b05b09
commit 6f91c96de8
3 changed files with 426 additions and 179 deletions
+140 -179
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@@ -150,6 +150,103 @@ void SVD::ApplyGivensRight(Matrix<5, 5> &W, uint8_t i, uint8_t j, float c,
}
}
// ============================================================================
// Phase 3: Extract and Sort Singular Values
// ============================================================================
void SVD::ExtractAndSortSingularValues(Matrix<5, 5> &W,
Matrix<5, 1> &sigma,
uint8_t p,
Matrix<5, 5> &QL,
Matrix<5, 5> &QR) {
// Extract singular values as absolute values of diagonal elements
for (uint8_t i = 0; i < p; i++) {
sigma[i][0] = fabsf(W[i][i]);
}
// Sort singular values in descending order and reorder U, V accordingly
for (uint8_t i = 0; i < p - 1; i++) {
for (uint8_t j = i + 1; j < p; j++) {
if (sigma[j][0] > sigma[i][0]) {
// Swap singular values
float tmpS = sigma[i][0];
sigma[i][0] = sigma[j][0];
sigma[j][0] = tmpS;
// Swap columns of QL
for (uint8_t k = 0; k < 5; k++) {
float tmpQ = QL[k][i];
QL[k][i] = QL[k][j];
QL[k][j] = tmpQ;
}
// Swap columns of QR
for (uint8_t k = 0; k < 5; k++) {
float tmpQ = QR[k][i];
QR[k][i] = QR[k][j];
QR[k][j] = tmpQ;
}
}
}
}
}
// ============================================================================
// Phase 4: Assemble Final U and Vt Matrices
// ============================================================================
void SVD::AssembleUAndVt(uint8_t m, uint8_t n, uint8_t p,
bool transposeNeeded,
const Matrix<5, 5> &QL,
const Matrix<5, 5> &QR,
Matrix<5, 5> &U,
Matrix<5, 5> &Vt) {
// Initialize output matrices to zero
for (uint8_t i = 0; i < 5; i++)
for (uint8_t j = 0; j < 5; j++) {
U[i][j] = 0;
Vt[i][j] = 0;
}
// ---- Compute Final U and Vt ----
// If transposeNeeded (wide matrix), we computed SVD(Aᵀ) = Ũ·Σ·Ṽᵀ
// Then U = Ṽ (= QR[:,0:p]) and Vt = Ũᵀ (= QL[:,0:p]ᵀ)
// Otherwise, SVD(A) = QL[:,0:p] · Σ · (QR[:,0:p])ᵀ
// So U = QL[:,0:p] and Vt = QR[:,0:p]ᵀ
for (uint8_t i = 0; i < m; i++) {
for (uint8_t j = 0; j < n; j++) {
if (j < p) {
if (transposeNeeded) {
// U = QR[:, 0:p]ᵀ → U[i][j] = QR[j][i]
U[i][j] = QR.Get(j, i);
} else {
// U = QL[:, 0:p]
U[i][j] = QL.Get(i, j);
}
} else {
U[i][j] = 0;
}
}
}
for (uint8_t i = 0; i < n; i++) {
for (uint8_t j = 0; j < m; j++) {
if (i < p && j < m) {
if (transposeNeeded) {
// Vt = QL[:, 0:p]ᵀ → Vt[i][j] = QL[j][i]
Vt[i][j] = QL.Get(j, i);
} else {
// Vt = QR[:, 0:p]ᵀ → Vt[i][j] = QR[j][i]
Vt[i][j] = QR.Get(j, i);
}
} else {
Vt[i][j] = 0;
}
}
}
}
// ============================================================================
// SVD Implementation - Golub-Kahan-Reinsch Algorithm
// ============================================================================
@@ -224,122 +321,45 @@ void SVD::SVD(Matrix<rows, columns> &matrixToDecompose,
x[i] = W[k + i][k];
}
// Compute Householder reflection: H·x = [α, 0, ..., 0]ᵀ
float norm = 0;
for (uint8_t i = 0; i < len; i++)
norm += x[i] * x[i];
norm = sqrtf(norm);
// Use building block to compute Householder reflector
float alpha;
SVD::ComputeHouseholder(x, len, hhVec, alpha);
if (norm < 1e-30f)
if (alpha == 0.0f)
continue;
float alpha = (x[0] >= 0) ? -norm : norm;
float v0 = x[0] - alpha;
float vv = v0 * v0 + norm * norm - alpha * x[0];
if (vv < 1e-30f)
continue;
float scale = 1.0f / sqrtf(vv);
// Store Householder vector (first element is implicit 1, rest in hhVec)
hhVec[0] =
v0 * scale; // this is the first element of the reflected vector
for (uint8_t i = 1; i < len; i++) {
hhVec[i] = x[i] * scale;
}
// Apply H from left to W: W = H·W
// For each column j, w[k+i][j] -= 2·v_i·(vᵀ·w_col) / (vᵀv)
float vvNorm = 1.0f + hhVec[0] * hhVec[0];
for (uint8_t i = 1; i < len; i++) {
vvNorm += hhVec[i] * hhVec[i];
}
for (uint8_t j = k; j < n; j++) {
float dot = 0;
for (uint8_t i = 0; i < len; i++) {
dot += hhVec[i] * W[k + i][j];
}
dot *= 2.0f / vvNorm;
for (uint8_t i = 0; i < len; i++) {
W[k + i][j] -= dot * hhVec[i];
}
}
SVD::ApplyHouseholderLeft(W, hhVec, k, k + len - 1);
// Apply H from right to QL: QL = QL · H
for (uint8_t j = k; j < m; j++) {
float dot = 0;
for (uint8_t i = 0; i < len; i++) {
dot += hhVec[i] * QL[j][k + i];
}
dot *= 2.0f / vvNorm;
for (uint8_t i = 0; i < len; i++) {
QL[j][k + i] -= dot * hhVec[i];
}
}
SVD::ApplyHouseholderRight(QL, hhVec, k, k + len - 1);
}
// --- Right Householder on row k, columns k+1..min(m,n)-1 ---
// --- Right Householder on row k, columns k+2..min(m,n)-1 ---
// (column k+1 is the first superdiagonal element, preserved in bidiagonal form)
{
uint8_t len = (p > 1) ? p - 1 - k : 0;
uint8_t len = (p > 1) ? p - 2 - k : 0;
if (len <= 0)
continue;
// Extract the row segment
// Extract the row segment starting from column k+2
float x[5];
for (uint8_t i = 0; i < len; i++) {
x[i] = W[k][k + 1 + i];
x[i] = W[k][k + 2 + i];
}
// Compute Householder reflection
float norm = 0;
for (uint8_t i = 0; i < len; i++)
norm += x[i] * x[i];
norm = sqrtf(norm);
// Use building block to compute Householder reflector
float alpha;
SVD::ComputeHouseholder(x, len, hhVec, alpha);
if (norm < 1e-30f)
if (alpha == 0.0f)
continue;
float alpha = (x[0] >= 0) ? -norm : norm;
float v0 = x[0] - alpha;
float vv = v0 * v0 + norm * norm - alpha * x[0];
if (vv < 1e-30f)
continue;
float scale = 1.0f / sqrtf(vv);
hhVec[0] = v0 * scale;
for (uint8_t i = 1; i < len; i++) {
hhVec[i] = x[i] * scale;
}
// Compute vᵀv
float vvNorm = 1.0f + hhVec[0] * hhVec[0];
for (uint8_t i = 1; i < len; i++) {
vvNorm += hhVec[i] * hhVec[i];
}
// Apply H from right to W: W = W·H
for (uint8_t i = 0; i < m; i++) {
float dot = 0;
for (uint8_t j = 0; j < len; j++) {
dot += hhVec[j] * W[i][k + 1 + j];
}
dot *= 2.0f / vvNorm;
for (uint8_t j = 0; j < len; j++) {
W[i][k + 1 + j] -= dot * hhVec[j];
}
}
SVD::ApplyHouseholderRight(W, hhVec, k + 2, k + 1 + len);
// Apply H from right to QR: QR = QR · H
for (uint8_t i = 0; i < n; i++) {
float dot = 0;
for (uint8_t j = 0; j < len; j++) {
dot += hhVec[j] * QR[i][k + 1 + j];
}
dot *= 2.0f / vvNorm;
for (uint8_t j = 0; j < len; j++) {
QR[i][k + 1 + j] -= dot * hhVec[j];
}
}
SVD::ApplyHouseholderRight(QR, hhVec, k + 2, k + 1 + len);
}
}
@@ -425,32 +445,15 @@ void SVD::SVD(Matrix<rows, columns> &matrixToDecompose,
float y = (start > 0) ? W[start][start - 1] : 0.0f;
for (uint8_t i = start; i <= end; i++) {
float r = sqrtf(x * x + y * y);
if (r < 1e-30f) {
x = W[i][i];
y = (i < end) ? W[i + 1][i] : 0.0f;
continue;
}
float cs = x / r;
float sn = y / r;
float cs, sn;
SVD::ComputeGivens(x, y, cs, sn);
// Apply Givens from left to rows i, i+1 of W (columns i..p-1)
for (uint8_t j = i; j < p; j++) {
float t1 = W[i][j];
float t2 = W[i + 1][j];
W[i][j] = cs * t1 + sn * t2;
W[i + 1][j] = -sn * t1 + cs * t2;
}
SVD::ApplyGivensLeft(W, i, i + 1, cs, sn, i, p - 1);
// Apply Givens from right to columns i, i+1 of W (rows 0..i)
if (i > start) {
for (uint8_t j = 0; j <= i; j++) {
float t1 = W[j][i];
float t2 = W[j][i + 1];
W[j][i] = cs * t1 + sn * t2;
W[j][i + 1] = -sn * t1 + cs * t2;
}
SVD::ApplyGivensRight(W, i, i + 1, cs, sn, 0, i);
}
// Accumulate right transformations into QR
@@ -462,77 +465,35 @@ void SVD::SVD(Matrix<rows, columns> &matrixToDecompose,
}
// Prepare next Givens rotation
x = W[i + 1][i];
y = (i + 1 < end) ? W[i + 1][i + 1] : 0.0f;
}
}
// ---- Phase 3: Extract Results ----
// Singular values are the absolute values of diagonal elements of W
for (uint8_t i = 0; i < p; i++) {
sigma[i][0] = fabsf(W[i][i]);
}
// Sort singular values in descending order and reorder U, V accordingly
for (uint8_t i = 0; i < p - 1; i++) {
for (uint8_t j = i + 1; j < p; j++) {
if (sigma[j][0] > sigma[i][0]) {
float tmpS = sigma[i][0];
sigma[i][0] = sigma[j][0];
sigma[j][0] = tmpS;
// Swap columns of QL
for (uint8_t k = 0; k < 5; k++) {
float tmpQ = QL[k][i];
QL[k][i] = QL[k][j];
QL[k][j] = tmpQ;
}
// Swap columns of QR
for (uint8_t k = 0; k < 5; k++) {
float tmpQ = QR[k][i];
QR[k][i] = QR[k][j];
QR[k][j] = tmpQ;
}
if (i + 1 <= end) {
x = W[i + 1][i];
y = (i + 1 < end) ? W[i + 1][i + 1] : 0.0f;
}
}
}
// ---- Phase 4: Compute Final U and Vt ----
// If transposeNeeded (wide matrix), we computed SVD(Aᵀ) = Ũ·Σ·Ṽᵀ
// Then U = Ṽ (= QR[:,0:p]) and Vt = Ũᵀ (= QL[:,0:p]ᵀ)
// Otherwise, SVD(A) = QL[:,0:p] · Σ · (QR[:,0:p])ᵀ
// So U = QL[:,0:p] and Vt = QR[:,0:p]ᵀ
// ---- Phase 3: Extract and Sort Singular Values ----
// Use internal 5×1 buffer for sigma
Matrix<5, 1> sigmaInternal{0};
ExtractAndSortSingularValues(W, sigmaInternal, p, QL, QR);
for (uint8_t i = 0; i < m; i++) {
for (uint8_t j = 0; j < n; j++) {
if (j < p) {
if (transposeNeeded) {
// U = QR[:, 0:p]ᵀ → U[i][j] = QR[j][i]
U[i][j] = QR[j][i];
} else {
// U = QL[:, 0:p]
U[i][j] = QL[i][j];
}
} else {
U[i][j] = 0;
}
// ---- Phase 4: Assemble Final U and Vt ----
// Use internal 5×5 buffers for U and Vt
Matrix<5, 5> UInternal{0}, VtInternal{0};
AssembleUAndVt(m, n, p, transposeNeeded, QL, QR, UInternal, VtInternal);
// Copy results to output parameters
for (uint8_t i = 0; i < columns; i++) {
sigma[i][0] = sigmaInternal.Get(i, 0);
}
for (uint8_t i = 0; i < rows; i++) {
for (uint8_t j = 0; j < columns; j++) {
U[i][j] = UInternal.Get(i, j);
}
}
for (uint8_t i = 0; i < n; i++) {
for (uint8_t j = 0; j < m; j++) {
if (i < p && j < m) {
if (transposeNeeded) {
// Vt = QL[:, 0:p]ᵀ → Vt[i][j] = QL[j][i]
Vt[i][j] = QL[j][i];
} else {
// Vt = QR[:, 0:p]ᵀ → Vt[i][j] = QR[j][i]
Vt[i][j] = QR[j][i];
}
} else {
Vt[i][j] = 0;
}
for (uint8_t i = 0; i < columns; i++) {
for (uint8_t j = 0; j < rows; j++) {
Vt[i][j] = VtInternal.Get(i, j);
}
}
}
+44
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@@ -78,6 +78,50 @@ static void ApplyHouseholderLeft(Matrix<5, 5> &W, const float *v,
static void ApplyHouseholderRight(Matrix<5, 5> &W, const float *v,
uint8_t startCol, uint8_t endCol);
/**
* @brief Extract singular values from bidiagonal matrix diagonal and sort.
*
* Extracts absolute values of diagonal elements of W as singular values,
* then sorts them in descending order while reordering columns of QL
* and QR to maintain consistency.
*
* @param W Input: bidiagonal matrix (5×5 working array)
* @param sigma Output: sorted singular values (5×1 column vector, only first p used)
* @param p Number of singular values (min(rows, columns))
* @param QL Input/output: left transformation matrix (modified during sort)
* @param QR Input/output: right transformation matrix (modified during sort)
*/
static void ExtractAndSortSingularValues(Matrix<5, 5> &W,
Matrix<5, 1> &sigma,
uint8_t p,
Matrix<5, 5> &QL,
Matrix<5, 5> &QR);
/**
* @brief Assemble final U and Vt matrices from QL/QR.
*
* Computes the final left singular vectors (U) and right singular vectors
* transposed (Vt) from the accumulated Householder transformations.
*
* For non-transpose case: U = QL[:,0:p], Vt = QR[:,0:p]ᵀ
* For transpose case: U = QR[:,0:p]ᵀ, Vt = QL[:,0:p]ᵀ
*
* @param m Number of rows in original matrix
* @param n Number of columns in original matrix
* @param p Rank = min(m, n)
* @param transposeNeeded True if we computed SVD(Aᵀ) instead of SVD(A)
* @param QL Left Householder accumulation (5×5)
* @param QR Right Householder accumulation (5×5)
* @param U Output: left singular vectors (m×n matrix, only first p columns used)
* @param Vt Output: right singular vectors transposed (n×n matrix, only first p rows used)
*/
static void AssembleUAndVt(uint8_t m, uint8_t n, uint8_t p,
bool transposeNeeded,
const Matrix<5, 5> &QL,
const Matrix<5, 5> &QR,
Matrix<5, 5> &U,
Matrix<5, 5> &Vt);
/**
* @brief Compute a Givens rotation that zeros out y.
*
+242
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@@ -783,3 +783,245 @@ TEST_CASE("SVD Building Block: Givens preserves orthogonality",
REQUIRE(isOrthogonal5(M_right));
}
}
// ============================================================================
// TEST 11: ExtractAndSortSingularValues (Phase 3)
// ===========================================================================
TEST_CASE("SVD Phase 3: ExtractAndSortSingularValues", "[Matrix][SVD]") {
// Test case 1: Diagonal matrix with unordered singular values
{
Matrix<5, 5> W{0};
W[0][0] = 2.0f;
W[1][1] = 10.0f;
W[2][2] = 5.0f;
Matrix<5, 1> sigma{0};
Matrix<5, 5> QL{0}, QR{0};
for (uint8_t i = 0; i < 5; i++) {
QL[i][i] = 1.0f;
QR[i][i] = 1.0f;
}
SVD::ExtractAndSortSingularValues(W, sigma, 3, QL, QR);
// Singular values should be sorted descending: [10, 5, 2]
REQUIRE_THAT(sigma.Get(0, 0), Catch::Matchers::WithinRel(10.0f, 1e-6f));
REQUIRE_THAT(sigma.Get(1, 0), Catch::Matchers::WithinRel(5.0f, 1e-6f));
REQUIRE_THAT(sigma.Get(2, 0), Catch::Matchers::WithinRel(2.0f, 1e-6f));
// QL and QR columns should have been swapped to match the sort order
// Original: col 0 → σ=2, col 1 → σ=10, col 2 → σ=5
// After sort: col 0 has σ=10 (was orig col 1), col 1 has σ=5 (was orig col 2),
// col 2 has σ=2 (was orig col 0)
// Starting from identity: QL[:,0] = e₀, QL[:,1] = e₁, QL[:,2] = e₂
// After swaps: QL[:,0] = e₁, QL[:,1] = e₂, QL[:,2] = e₀
REQUIRE_THAT(QL.Get(0, 0), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(QL.Get(1, 0), Catch::Matchers::WithinRel(1.0f, 1e-6f));
REQUIRE_THAT(QL.Get(2, 0), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(QL.Get(0, 1), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(QL.Get(1, 1), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(QL.Get(2, 1), Catch::Matchers::WithinRel(1.0f, 1e-6f));
REQUIRE_THAT(QL.Get(0, 2), Catch::Matchers::WithinRel(1.0f, 1e-6f));
REQUIRE_THAT(QL.Get(1, 2), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(QL.Get(2, 2), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
}
// Test case 2: Negative diagonal elements (absolute value extraction)
{
Matrix<5, 5> W{0};
W[0][0] = -3.0f;
W[1][1] = -7.0f;
W[2][2] = 5.0f;
Matrix<5, 1> sigma{0};
Matrix<5, 5> QL{0}, QR{0};
for (uint8_t i = 0; i < 5; i++) {
QL[i][i] = 1.0f;
QR[i][i] = 1.0f;
}
SVD::ExtractAndSortSingularValues(W, sigma, 3, QL, QR);
// Should extract absolute values and sort: [7, 5, 3]
REQUIRE_THAT(sigma.Get(0, 0), Catch::Matchers::WithinRel(7.0f, 1e-6f));
REQUIRE_THAT(sigma.Get(1, 0), Catch::Matchers::WithinRel(5.0f, 1e-6f));
REQUIRE_THAT(sigma.Get(2, 0), Catch::Matchers::WithinRel(3.0f, 1e-6f));
}
// Test case 3: Already sorted (no swaps needed)
{
Matrix<5, 5> W{0};
W[0][0] = 9.0f;
W[1][1] = 6.0f;
W[2][2] = 3.0f;
Matrix<5, 1> sigma{0};
Matrix<5, 5> QL{0}, QR{0};
for (uint8_t i = 0; i < 5; i++) {
QL[i][i] = 1.0f;
QR[i][i] = 1.0f;
}
SVD::ExtractAndSortSingularValues(W, sigma, 3, QL, QR);
REQUIRE_THAT(sigma.Get(0, 0), Catch::Matchers::WithinRel(9.0f, 1e-6f));
REQUIRE_THAT(sigma.Get(1, 0), Catch::Matchers::WithinRel(6.0f, 1e-6f));
REQUIRE_THAT(sigma.Get(2, 0), Catch::Matchers::WithinRel(3.0f, 1e-6f));
// QL and QR should be unchanged (identity)
for (uint8_t i = 0; i < 5; i++) {
for (uint8_t j = 0; j < 5; j++) {
float expected = (i == j) ? 1.0f : 0.0f;
REQUIRE_THAT(QL.Get(i, j), Catch::Matchers::WithinRel(expected, 1e-6f));
REQUIRE_THAT(QR.Get(i, j), Catch::Matchers::WithinRel(expected, 1e-6f));
}
}
}
// Test case 4: Single singular value
{
Matrix<5, 5> W{0};
W[0][0] = 42.0f;
Matrix<5, 1> sigma{0};
Matrix<5, 5> QL{0}, QR{0};
for (uint8_t i = 0; i < 5; i++) {
QL[i][i] = 1.0f;
QR[i][i] = 1.0f;
}
SVD::ExtractAndSortSingularValues(W, sigma, 1, QL, QR);
REQUIRE_THAT(sigma.Get(0, 0), Catch::Matchers::WithinRel(42.0f, 1e-6f));
}
}
// ============================================================================
// TEST 12: AssembleUAndVt (Phase 4)
// ===========================================================================
TEST_CASE("SVD Phase 4: AssembleUAndVt", "[Matrix][SVD]") {
// Test case 1: Non-transpose case (m ≥ n) — U from QL, Vt from QRᵀ
{
uint8_t m = 3, n = 2, p = 2;
bool transposeNeeded = false;
Matrix<5, 5> QL{0};
// Make columns orthonormal
QL[0][0] = 3.0f / 5.0f;
QL[1][0] = 4.0f / 5.0f;
QL[2][0] = 0.0f;
QL[0][1] = 4.0f / 5.0f;
QL[1][1] = -3.0f / 5.0f;
QL[2][1] = 0.0f;
Matrix<5, 5> QR{0};
QR[0][0] = 1.0f; // Vt[:,0]ᵀ
QR[1][0] = 0.0f;
QR[0][1] = 0.0f; // Vt[:,1]ᵀ
QR[1][1] = 1.0f;
Matrix<5, 5> U{0};
Matrix<5, 5> Vt{0};
SVD::AssembleUAndVt(m, n, p, transposeNeeded, QL, QR, U, Vt);
// U should be QL[:,0:2]
REQUIRE_THAT(U.Get(0, 0), Catch::Matchers::WithinRel(3.0f / 5.0f, 1e-6f));
REQUIRE_THAT(U.Get(1, 0), Catch::Matchers::WithinRel(4.0f / 5.0f, 1e-6f));
REQUIRE_THAT(U.Get(2, 0), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(U.Get(0, 1), Catch::Matchers::WithinRel(4.0f / 5.0f, 1e-6f));
REQUIRE_THAT(U.Get(1, 1), Catch::Matchers::WithinRel(-3.0f / 5.0f, 1e-6f));
REQUIRE_THAT(U.Get(2, 1), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
// Vt should be QR[:,0:2]ᵀ
REQUIRE_THAT(Vt.Get(0, 0), Catch::Matchers::WithinRel(1.0f, 1e-6f));
REQUIRE_THAT(Vt.Get(0, 1), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(Vt.Get(1, 0), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(Vt.Get(1, 1), Catch::Matchers::WithinRel(1.0f, 1e-6f));
// Verify U is orthogonal (first p columns)
Matrix<5, 5> Ut = U.Transpose();
Matrix<5, 5> UtU{0};
Ut.Mult(U, UtU);
REQUIRE_THAT(UtU.Get(0, 0), Catch::Matchers::WithinRel(1.0f, 1e-6f));
REQUIRE_THAT(UtU.Get(0, 1), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(UtU.Get(1, 0), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(UtU.Get(1, 1), Catch::Matchers::WithinRel(1.0f, 1e-6f));
}
// Test case 2: Transpose case (m < n) — U from QRᵀ, Vt from QLᵀ
{
uint8_t m = 2, n = 3, p = 2;
bool transposeNeeded = true;
Matrix<5, 5> QL{0};
QL[0][0] = 1.0f; // Vt[:,0]ᵀ
QL[1][0] = 0.0f;
QL[0][1] = 0.0f; // Vt[:,1]ᵀ
QL[1][1] = 1.0f;
Matrix<5, 5> QR{0};
QR[0][0] = 3.0f / 5.0f; // U[:,0]
QR[1][0] = 4.0f / 5.0f;
QR[2][0] = 0.0f;
QR[0][1] = 4.0f / 5.0f;
QR[1][1] = -3.0f / 5.0f;
QR[2][1] = 0.0f;
Matrix<5, 5> U{0};
Matrix<5, 5> Vt{0};
SVD::AssembleUAndVt(m, n, p, transposeNeeded, QL, QR, U, Vt);
// U should be QR[:,0:2]ᵀ → U[i][j] = QR[j][i]
REQUIRE_THAT(U.Get(0, 0), Catch::Matchers::WithinRel(3.0f / 5.0f, 1e-6f));
REQUIRE_THAT(U.Get(0, 1), Catch::Matchers::WithinRel(4.0f / 5.0f, 1e-6f));
REQUIRE_THAT(U.Get(1, 0), Catch::Matchers::WithinRel(4.0f / 5.0f, 1e-6f));
REQUIRE_THAT(U.Get(1, 1), Catch::Matchers::WithinRel(-3.0f / 5.0f, 1e-6f));
// Vt should be QL[:,0:2]ᵀ → Vt[i][j] = QL[j][i]
REQUIRE_THAT(Vt.Get(0, 0), Catch::Matchers::WithinRel(1.0f, 1e-6f));
REQUIRE_THAT(Vt.Get(0, 1), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(Vt.Get(1, 0), Catch::Matchers::WithinAbs(0.0f, 1e-6f));
REQUIRE_THAT(Vt.Get(1, 1), Catch::Matchers::WithinRel(1.0f, 1e-6f));
// Verify U has correct dimensions (m×n = 2×3)
REQUIRE(U.Get(0, 2) == 0.0f);
REQUIRE(U.Get(1, 2) == 0.0f);
// Verify Vt is orthogonal (first p rows)
Matrix<5, 5> VtVtT{0};
Vt.Mult(Vt.Transpose(), VtVtT);
REQUIRE_THAT(VtVtT.Get(0, 0), Catch::Matchers::WithinRel(1.0f, 1e-6f));
REQUIRE_THAT(VtVtT.Get(1, 1), Catch::Matchers::WithinRel(1.0f, 1e-6f));
// Row 2 of Vt is all zeros (p=2 < n=3), so VtVtT[2][2] = 0 is expected
}
// Test case 3: Square matrix (m = n)
{
uint8_t m = 2, n = 2, p = 2;
bool transposeNeeded = false;
Matrix<5, 5> QL{0};
QL[0][0] = 1.0f; QL[1][1] = 1.0f;
Matrix<5, 5> QR{0};
QR[0][0] = 0.6f; QR[0][1] = 0.8f;
QR[1][0] = 0.8f; QR[1][1] = -0.6f;
Matrix<5, 5> U{0};
Matrix<5, 5> Vt{0};
SVD::AssembleUAndVt(m, n, p, transposeNeeded, QL, QR, U, Vt);
// U = QL[:,0:2]
REQUIRE_THAT(U.Get(0, 0), Catch::Matchers::WithinRel(1.0f, 1e-6f));
REQUIRE_THAT(U.Get(1, 1), Catch::Matchers::WithinRel(1.0f, 1e-6f));
// Vt = QR[:,0:2]ᵀ
REQUIRE_THAT(Vt.Get(0, 0), Catch::Matchers::WithinRel(0.6f, 1e-6f));
REQUIRE_THAT(Vt.Get(0, 1), Catch::Matchers::WithinRel(0.8f, 1e-6f));
REQUIRE_THAT(Vt.Get(1, 0), Catch::Matchers::WithinRel(0.8f, 1e-6f));
REQUIRE_THAT(Vt.Get(1, 1), Catch::Matchers::WithinRel(-0.6f, 1e-6f));
}
}