/// <summary>
/// Initializes eigenvalue decomposition.
/// </summary>
/// <param name="A">Square matrix</param>
/// <param name="eps">Epsilon [0, 1]</param>
public EVD(float[,] A, float eps = 1e-16f)
{
if (!Matrice.IsSquare(A))
{
throw new Exception("The matrix must be square");
}
this.n = A.GetLength(0);
this.Re = new float[n];
this.Im = new float[n];
this.eps = Maths.Float(eps);
// for symmetric matrices eigen-value decomposition
// without Hessenberg form.
if (Matrice.IsSymmetric(A))
{
hessenberg = Jagged.Zero(n, n);
matrices = Jagged.ToJagged(A);
tred2(); // Tridiagonalize.
tql2(); // Diagonalize.
}
// with Hessenberg form.
else
{
matrices = Jagged.Zero(n, n);
hessenberg = Jagged.ToJagged(A);
orthogonal = new float[n];
orthes(); // Reduce to Hessenberg form.
hqr2(); // Reduce Hessenberg to real Schur form.
}
}
/// <summary>
/// Initializes generalized eigenvalue decomposition.
/// </summary>
/// <param name="a">Matrix A</param>
/// <param name="b">Matrix B</param>
/// <param name="eps">Epsilon [0, 1]</param>
public GEVD(float[,] a, float[,] b, float eps = 1e-16f)
{
if (a.GetLength(0) != a.GetLength(1))
{
throw new ArgumentException("The matrix must be square");
}
if (b.GetLength(0) != b.GetLength(1))
{
throw new ArgumentException("The matrix must be square");
}
if (a.GetLength(0) != b.GetLength(0) || a.GetLength(1) != b.GetLength(1))
{
throw new ArgumentException("Matrices should be the same size");
}
// params
this.n = a.GetLength(0);
this.ar = new float[n];
this.ai = new float[n];
this.beta = new float[n];
this.Z = Jagged.Zero(n, n);
var A = Jagged.ToJagged(a);
var B = Jagged.ToJagged(b);
bool matz = true;
int ierr = 0;
// reduces A to upper Hessenberg form and B to upper
// triangular form using orthogonal transformations
qzhes(n, A, B, matz, Z);
// reduces the Hessenberg matrix A to quasi-triangular form
// using orthogonal transformations while maintaining the
// triangular form of the B matrix.
qzit(n, A, B, Maths.Float(eps), matz, Z, ref ierr);
// reduces the quasi-triangular matrix further, so that any
// remaining 2-by-2 blocks correspond to pairs of complex
// eigenvalues, and returns quantities whose ratios give the
// generalized eigenvalues.
qzval(n, A, B, ar, ai, beta, matz, Z);
// computes the eigenvectors of the triangular problem and
// transforms the results back to the original coordinate system.
qzvec(n, A, B, ar, ai, beta, Z);
}
/// <summary>
///
/// </summary>
/// <param name="a"></param>
private void ludecomp(float[][] a)
{
int i, j, k;
int n = a.GetLength(0);
float alpha, beta;
this.upper = Jagged.Zero(n, n);
this.lower = Jagged.Zero(n, n);
for (i = 0; i < n; i++)
{
this.upper[i][i] = 1;
}
for (j = 0; j < n; j++)
{
for (i = j; i < n; i++)
{
alpha = 0;
for (k = 0; k < j; k++)
{
alpha = alpha + this.lower[i][k] * this.upper[k][j];
}
this.lower[i][j] = a[i][j] - alpha;
}
beta = lower[j][j];
for (i = j; i < n; i++)
{
alpha = 0;
for (k = 0; k < j; k++)
{
alpha = alpha + this.lower[j][k] * this.upper[k][i];
}
if (beta != 0)
{
this.upper[j][i] = (a[j][i] - alpha) / beta;
}
}
}
}
/// <summary>
///
/// </summary>
/// <param name="A"></param>
private void svdcmp(float[,] A)
{
this.Ur = Jagged.ToJagged(A);
this.Sr = new float[m];
this.Vr = Jagged.Zero(m, m);
float[] rv1 = new float[m];
int flag, i, its, j, jj, k, l = 0, nm = 0;
float anorm, c, f, g, h, e, scale, x, y, z;
// householder reduction to bidiagonal form
g = scale = anorm = 0.0f;
for (i = 0; i < m; i++)
{
l = i + 1;
rv1[i] = scale * g;
g = e = scale = 0;
if (i < n)
{
for (k = i; k < n; k++)
{
scale += Math.Abs(Ur[k][i]);
}
if (scale != 0.0)
{
for (k = i; k < n; k++)
{
Ur[k][i] /= scale;
e += Ur[k][i] * Ur[k][i];
}
f = Ur[i][i];
g = -Sign((float)Math.Sqrt(e), f);
h = f * g - e;
Ur[i][i] = f - g;
if (i != m - 1)
{
for (j = l; j < m; j++)
{
for (e = 0.0f, k = i; k < n; k++)
{
e += Ur[k][i] * Ur[k][j];
}
f = e / h;
for (k = i; k < n; k++)
{
Ur[k][j] += f * Ur[k][i];
}
}
}
for (k = i; k < n; k++)
{
Ur[k][i] *= scale;
}
}
}
Sr[i] = scale * g;
g = e = scale = 0.0f;
if ((i < n) && (i != m - 1))
{
for (k = l; k < m; k++)
{
scale += Math.Abs(Ur[i][k]);
}
if (scale != 0.0)
{
for (k = l; k < m; k++)
{
Ur[i][k] /= scale;
e += Ur[i][k] * Ur[i][k];
}
f = Ur[i][l];
g = -Sign((float)Math.Sqrt(e), f);
h = f * g - e;
Ur[i][l] = f - g;
for (k = l; k < m; k++)
{
rv1[k] = Ur[i][k] / h;
}
if (i != n - 1)
{
for (j = l; j < n; j++)
{
for (e = 0.0f, k = l; k < m; k++)
{
e += Ur[j][k] * Ur[i][k];
}
for (k = l; k < m; k++)
{
Ur[j][k] += e * rv1[k];
}
}
}
for (k = l; k < m; k++)
{
Ur[i][k] *= scale;
}
}
}
anorm = Math.Max(anorm, (Math.Abs(Sr[i]) + Math.Abs(rv1[i])));
}
// accumulation of right-hand transformations
for (i = m - 1; i >= 0; i--)
{
if (i < m - 1)
{
if (g != 0.0)
{
for (j = l; j < m; j++)
{
Vr[j][i] = (Ur[i][j] / Ur[i][l]) / g;
}
for (j = l; j < m; j++)
{
for (e = 0, k = l; k < m; k++)
{
e += Ur[i][k] * Vr[k][j];
}
for (k = l; k < m; k++)
{
Vr[k][j] += e * Vr[k][i];
}
}
}
for (j = l; j < m; j++)
{
Vr[i][j] = Vr[j][i] = 0;
}
}
Vr[i][i] = 1;
g = rv1[i];
l = i;
}
// accumulation of left-hand transformations
for (i = m - 1; i >= 0; i--)
{
l = i + 1;
g = Sr[i];
if (i < m - 1)
{
for (j = l; j < m; j++)
{
Ur[i][j] = 0.0f;
}
}
if (g != 0)
{
g = 1.0f / g;
if (i != m - 1)
{
for (j = l; j < m; j++)
{
for (e = 0, k = l; k < n; k++)
{
e += Ur[k][i] * Ur[k][j];
}
f = (e / Ur[i][i]) * g;
for (k = i; k < n; k++)
{
Ur[k][j] += f * Ur[k][i];
}
}
}
for (j = i; j < n; j++)
{
Ur[j][i] *= g;
}
}
else
{
for (j = i; j < n; j++)
{
Ur[j][i] = 0;
}
}
++Ur[i][i];
}
// diagonalization of the bidiagonal form: Loop over singular values
// and over allowed iterations
for (k = m - 1; k >= 0; k--)
{
for (its = 1; its <= iterations; its++)
{
flag = 1;
for (l = k; l >= 0; l--)
{
// test for splitting
nm = l - 1;
if (Math.Abs(rv1[l]) + anorm == anorm)
{
flag = 0;
break;
}
if (Math.Abs(Sr[nm]) + anorm == anorm)
{
break;
}
}
if (flag != 0)
{
c = 0.0f;
e = 1.0f;
for (i = l; i <= k; i++)
{
f = e * rv1[i];
if (Math.Abs(f) + anorm != anorm)
{
g = Sr[i];
h = Maths.Hypotenuse(f, g);
Sr[i] = h;
h = 1.0f / h;
c = g * h;
e = -f * h;
//for (j = 1; j <= m; j++)
for (j = 1; j < n; j++)
{
y = Ur[j][nm];
z = Ur[j][i];
Ur[j][nm] = y * c + z * e;
Ur[j][i] = z * c - y * e;
}
}
}
}
z = Sr[k];
if (l == k)
{
// convergence
if (z < 0.0)
{
// singular value is made nonnegative
Sr[k] = -z;
for (j = 0; j < m; j++)
{
Vr[j][k] = -Vr[j][k];
}
}
break;
}
if (its == iterations)
{
throw new ApplicationException("No convergence in " + iterations.ToString() + " iterations of singular decomposition");
}
// shift from bottom 2-by-2 minor
x = Sr[l];
nm = k - 1;
y = Sr[nm];
g = rv1[nm];
h = rv1[k];
f = ((y - z) * (y + z) + (g - h) * (g + h)) / (2.0f * h * y);
g = Maths.Hypotenuse(f, 1.0f);
f = ((x - z) * (x + z) + h * ((y / (f + Sign(g, f))) - h)) / x;
// next QR transformation
c = e = 1.0f;
for (j = l; j <= nm; j++)
{
i = j + 1;
g = rv1[i];
y = Sr[i];
h = e * g;
g = c * g;
z = Maths.Hypotenuse(f, h);
rv1[j] = z;
c = f / z;
e = h / z;
f = x * c + g * e;
g = g * c - x * e;
h = y * e;
y *= c;
for (jj = 0; jj < m; jj++)
{
x = Vr[jj][j];
z = Vr[jj][i];
Vr[jj][j] = x * c + z * e;
Vr[jj][i] = z * c - x * e;
}
z = Maths.Hypotenuse(f, h);
Sr[j] = z;
if (z != 0)
{
z = 1.0f / z;
c = f * z;
e = h * z;
}
f = c * g + e * y;
x = c * y - e * g;
for (jj = 0; jj < n; jj++)
{
y = Ur[jj][j];
z = Ur[jj][i];
Ur[jj][j] = y * c + z * e;
Ur[jj][i] = z * c - y * e;
}
}
rv1[l] = 0.0f;
rv1[k] = f;
Sr[k] = x;
}
}
}
/// <summary>
///
/// </summary>
/// <param name="A"></param>
private void orthes(float[,] A)
{
// Properties
int n = A.GetLength(0);
this.matrices = Jagged.Zero(n, n);
this.hessenberg = Jagged.ToJagged(A);
float[] orthogonal = new float[n];
// Nonsymmetric reduction to Hessenberg form.
// This is derived from the Algol procedures orthes and ortran, by Martin and Wilkinson,
// Handbook for Auto. Comp., Vol.ii-Linear Algebra, and the corresponding Fortran subroutines in EISPACK.
int low = 0;
int high = n - 1;
int m, i, j;
float scale, h, g, f;
for (m = low + 1; m <= high - 1; m++)
{
// Scale column.
scale = 0;
for (i = m; i <= high; i++)
{
scale = scale + System.Math.Abs(hessenberg[i][m - 1]);
}
if (scale != 0)
{
// Compute Householder transformation.
h = 0;
for (i = high; i >= m; i--)
{
orthogonal[i] = hessenberg[i][m - 1] / scale;
h += orthogonal[i] * orthogonal[i];
}
g = (float)System.Math.Sqrt(h);
if (orthogonal[m] > 0)
{
g = -g;
}
h = h - orthogonal[m] * g;
orthogonal[m] = orthogonal[m] - g;
// Apply Householder similarity transformation
// H = (I - u * u' / h) * H * (I - u * u') / h)
for (j = m; j < n; j++)
{
f = 0;
for (i = high; i >= m; i--)
{
f += orthogonal[i] * hessenberg[i][j];
}
f = f / h;
for (i = m; i <= high; i++)
{
hessenberg[i][j] -= f * orthogonal[i];
}
}
for (i = 0; i <= high; i++)
{
f = 0;
for (j = high; j >= m; j--)
{
f += orthogonal[j] * hessenberg[i][j];
}
f = f / h;
for (j = m; j <= high; j++)
{
hessenberg[i][j] -= f * orthogonal[j];
}
}
orthogonal[m] = scale * orthogonal[m];
hessenberg[m][m - 1] = scale * g;
}
}
// Accumulate transformations (Algol's ortran).
for (i = 0; i < n; i++)
{
for (j = 0; j < n; j++)
{
matrices[i][j] = (i == j ? 1 : 0);
}
}
for (m = high - 1; m >= low + 1; m--)
{
if (hessenberg[m][m - 1] != 0)
{
for (i = m + 1; i <= high; i++)
{
orthogonal[i] = hessenberg[i][m - 1];
}
for (j = m; j <= high; j++)
{
g = 0;
for (i = m; i <= high; i++)
{
g += orthogonal[i] * matrices[i][j];
}
// float division avoids possible underflow.
g = (g / orthogonal[m]) / hessenberg[m][m - 1];
for (i = m; i <= high; i++)
{
matrices[i][j] += g * orthogonal[i];
}
}
}
}
// final reduction:
if (n > 2)
{
for (i = 0; i < n - 2; i++)
{
for (j = i + 2; j < n; j++)
{
hessenberg[j][i] = 0;
}
}
}
}
