Exemplo n.º 1
0
// SolveLUVec solves a system of linear equations using the LU decomposition of a matrix.
// It computes
//  A * x = b if trans == false
//  A^T * x = b if trans == true
// In both cases, A is represeneted in LU factorized form, and the matrix x is
// stored into the receiver.
//
// If A is singular or near-singular a Condition error is returned. Please see
// the documentation for Condition for more information.
func (v *Vector) SolveLUVec(lu *LU, trans bool, b *Vector) error {
	_, n := lu.lu.Dims()
	bn := b.Len()
	if bn != n {
		panic(matrix.ErrShape)
	}
	// TODO(btracey): Should test the condition number instead of testing that
	// the determinant is exactly zero.
	if lu.Det() == 0 {
		return matrix.Condition(math.Inf(1))
	}

	v.reuseAs(n)
	var restore func()
	if v == b {
		v, restore = v.isolatedWorkspace(b)
		defer restore()
	}
	v.CopyVec(b)
	vMat := blas64.General{
		Rows:   n,
		Cols:   1,
		Stride: v.mat.Inc,
		Data:   v.mat.Data,
	}
	t := blas.NoTrans
	if trans {
		t = blas.Trans
	}
	lapack64.Getrs(t, lu.lu.mat, vMat, lu.pivot)
	if lu.cond > matrix.ConditionTolerance {
		return matrix.Condition(lu.cond)
	}
	return nil
}
Exemplo n.º 2
0
// SolveLU solves a system of linear equations using the LU decomposition of a matrix.
// It computes
//  A * x = b if trans == false
//  A^T * x = b if trans == true
// In both cases, A is represented in LU factorized form, and the matrix x is
// stored into the receiver.
//
// If A is singular or near-singular a Condition error is returned. Please see
// the documentation for Condition for more information.
func (m *Dense) SolveLU(lu *LU, trans bool, b Matrix) error {
	_, n := lu.lu.Dims()
	br, bc := b.Dims()
	if br != n {
		panic(matrix.ErrShape)
	}
	// TODO(btracey): Should test the condition number instead of testing that
	// the determinant is exactly zero.
	if lu.Det() == 0 {
		return matrix.Condition(math.Inf(1))
	}

	m.reuseAs(n, bc)
	bU, _ := untranspose(b)
	var restore func()
	if m == bU {
		m, restore = m.isolatedWorkspace(bU)
		defer restore()
	} else if rm, ok := bU.(RawMatrixer); ok {
		m.checkOverlap(rm.RawMatrix())
	}

	m.Copy(b)
	t := blas.NoTrans
	if trans {
		t = blas.Trans
	}
	lapack64.Getrs(t, lu.lu.mat, m.mat, lu.pivot)
	if lu.cond > matrix.ConditionTolerance {
		return matrix.Condition(lu.cond)
	}
	return nil
}
Exemplo n.º 3
0
// SolveLQ finds a minimum-norm solution to a system of linear equations defined
// by the matrices A and b, where A is an m×n matrix represented in its LQ factorized
// form. If A is singular or near-singular a Condition error is returned. Please
// see the documentation for Condition for more information.
//
// The minimization problem solved depends on the input parameters.
//  If trans == false, find the minimum norm solution of A * X = b.
//  If trans == true, find X such that ||A*X - b||_2 is minimized.
// The solution matrix, X, is stored in place into the receiver.
func (m *Dense) SolveLQ(lq *LQ, trans bool, b Matrix) error {
	r, c := lq.lq.Dims()
	br, bc := b.Dims()

	// The LQ solve algorithm stores the result in-place into the right hand side.
	// The storage for the answer must be large enough to hold both b and x.
	// However, this method's receiver must be the size of x. Copy b, and then
	// copy the result into m at the end.
	if trans {
		if c != br {
			panic(matrix.ErrShape)
		}
		m.reuseAs(r, bc)
	} else {
		if r != br {
			panic(matrix.ErrShape)
		}
		m.reuseAs(c, bc)
	}
	// Do not need to worry about overlap between m and b because x has its own
	// independent storage.
	x := getWorkspace(max(r, c), bc, false)
	x.Copy(b)
	t := lq.lq.asTriDense(lq.lq.mat.Rows, blas.NonUnit, blas.Lower).mat
	if trans {
		work := make([]float64, 1)
		lapack64.Ormlq(blas.Left, blas.NoTrans, lq.lq.mat, lq.tau, x.mat, work, -1)
		work = make([]float64, int(work[0]))
		lapack64.Ormlq(blas.Left, blas.NoTrans, lq.lq.mat, lq.tau, x.mat, work, len(work))

		ok := lapack64.Trtrs(blas.Trans, t, x.mat)
		if !ok {
			return matrix.Condition(math.Inf(1))
		}
	} else {
		ok := lapack64.Trtrs(blas.NoTrans, t, x.mat)
		if !ok {
			return matrix.Condition(math.Inf(1))
		}
		for i := r; i < c; i++ {
			zero(x.mat.Data[i*x.mat.Stride : i*x.mat.Stride+bc])
		}
		work := make([]float64, 1)
		lapack64.Ormlq(blas.Left, blas.Trans, lq.lq.mat, lq.tau, x.mat, work, -1)
		work = make([]float64, int(work[0]))
		lapack64.Ormlq(blas.Left, blas.Trans, lq.lq.mat, lq.tau, x.mat, work, len(work))
	}
	// M was set above to be the correct size for the result.
	m.Copy(x)
	putWorkspace(x)
	if lq.cond > matrix.ConditionTolerance {
		return matrix.Condition(lq.cond)
	}
	return nil
}
Exemplo n.º 4
0
// InverseTri computes the inverse of the triangular matrix a, storing the result
// into the receiver. If a is ill-conditioned, a Condition error will be returned.
// Note that matrix inversion is numerically unstable, and should generally be
// avoided where possible, for example by using the Solve routines.
func (t *TriDense) InverseTri(a Triangular) error {
	if rt, ok := a.(RawTriangular); ok {
		t.checkOverlap(rt.RawTriangular())
	}
	n, _ := a.Triangle()
	t.reuseAs(a.Triangle())
	t.Copy(a)
	work := make([]float64, 3*n)
	iwork := make([]int, n)
	cond := lapack64.Trcon(matrix.CondNorm, t.mat, work, iwork)
	if math.IsInf(cond, 1) {
		return matrix.Condition(cond)
	}
	ok := lapack64.Trtri(t.mat)
	if !ok {
		return matrix.Condition(math.Inf(1))
	}
	if cond > matrix.ConditionTolerance {
		return matrix.Condition(cond)
	}
	return nil
}
Exemplo n.º 5
0
// Inverse computes the inverse of the matrix a, storing the result into the
// receiver. If a is ill-conditioned, a Condition error will be returned.
// Note that matrix inversion is numerically unstable, and should generally
// be avoided where possible, for example by using the Solve routines.
func (m *Dense) Inverse(a Matrix) error {
	// TODO(btracey): Special case for RawTriangular, etc.
	r, c := a.Dims()
	if r != c {
		panic(matrix.ErrSquare)
	}
	m.reuseAs(a.Dims())
	aU, aTrans := untranspose(a)
	switch rm := aU.(type) {
	case RawMatrixer:
		if m != aU || aTrans {
			if m == aU || m.checkOverlap(rm.RawMatrix()) {
				tmp := getWorkspace(r, c, false)
				tmp.Copy(a)
				m.Copy(tmp)
				putWorkspace(tmp)
				break
			}
			m.Copy(a)
		}
	default:
		if m != aU {
			m.Copy(a)
		} else if aTrans {
			// m and a share data so Copy cannot be used directly.
			tmp := getWorkspace(r, c, false)
			tmp.Copy(a)
			m.Copy(tmp)
			putWorkspace(tmp)
		}
	}
	ipiv := make([]int, r)
	lapack64.Getrf(m.mat, ipiv)
	work := make([]float64, 1, 4*r) // must be at least 4*r for cond.
	lapack64.Getri(m.mat, ipiv, work, -1)
	if int(work[0]) > 4*r {
		work = make([]float64, int(work[0]))
	} else {
		work = work[:4*r]
	}
	lapack64.Getri(m.mat, ipiv, work, len(work))
	norm := lapack64.Lange(matrix.CondNorm, m.mat, work)
	cond := lapack64.Gecon(matrix.CondNorm, m.mat, norm, work, ipiv) // reuse ipiv
	if cond > matrix.ConditionTolerance {
		return matrix.Condition(cond)
	}
	return nil
}
Exemplo n.º 6
0
// SolveCholesky finds the matrix m that solves A * m = b where A is represented
// by the cholesky decomposition, placing the result in the receiver.
func (m *Dense) SolveCholesky(chol *Cholesky, b Matrix) error {
	n := chol.chol.mat.N
	bm, bn := b.Dims()
	if n != bm {
		panic(matrix.ErrShape)
	}

	m.reuseAs(bm, bn)
	if b != m {
		m.Copy(b)
	}
	blas64.Trsm(blas.Left, blas.Trans, 1, chol.chol.mat, m.mat)
	blas64.Trsm(blas.Left, blas.NoTrans, 1, chol.chol.mat, m.mat)
	if chol.cond > matrix.ConditionTolerance {
		return matrix.Condition(chol.cond)
	}
	return nil
}
Exemplo n.º 7
0
// SolveCholeskyVec finds the vector v that solves A * v = b where A is represented
// by the Cholesky decomposition, placing the result in the receiver.
func (v *Vector) SolveCholeskyVec(chol *Cholesky, b *Vector) error {
	n := chol.chol.mat.N
	vn := b.Len()
	if vn != n {
		panic(matrix.ErrShape)
	}
	v.reuseAs(n)
	if v != b {
		v.CopyVec(b)
	}
	blas64.Trsv(blas.Trans, chol.chol.mat, v.mat)
	blas64.Trsv(blas.NoTrans, chol.chol.mat, v.mat)
	if chol.cond > matrix.ConditionTolerance {
		return matrix.Condition(chol.cond)
	}
	return nil

}
Exemplo n.º 8
0
// Solve finds a minimum-norm solution to a system of linear equations defined
// by the matrices a and b. If A is singular or near-singular, a Condition error
// is returned. Please see the documentation for Condition for more information.
//
// The minimization problem solved depends on the input parameters:
//  - if m >= n, find X such that ||A*X - B||_2 is minimized,
//  - if m < n, find the minimum norm solution of A * X = B.
// The solution matrix, X, is stored in-place into the receiver.
func (m *Dense) Solve(a, b Matrix) error {
	ar, ac := a.Dims()
	br, bc := b.Dims()
	if ar != br {
		panic(matrix.ErrShape)
	}
	m.reuseAs(ac, bc)

	// TODO(btracey): Add special cases for SymDense, etc.
	aU, aTrans := untranspose(a)
	bU, bTrans := untranspose(b)
	switch rma := aU.(type) {
	case RawTriangular:
		side := blas.Left
		tA := blas.NoTrans
		if aTrans {
			tA = blas.Trans
		}

		switch rm := bU.(type) {
		case RawMatrixer:
			if m != bU || bTrans {
				if m == bU || m.checkOverlap(rm.RawMatrix()) {
					tmp := getWorkspace(br, bc, false)
					tmp.Copy(b)
					m.Copy(tmp)
					putWorkspace(tmp)
					break
				}
				m.Copy(b)
			}
		default:
			if m != bU {
				m.Copy(b)
			} else if bTrans {
				// m and b share data so Copy cannot be used directly.
				tmp := getWorkspace(br, bc, false)
				tmp.Copy(b)
				m.Copy(tmp)
				putWorkspace(tmp)
			}
		}

		rm := rma.RawTriangular()
		blas64.Trsm(side, tA, 1, rm, m.mat)
		work := make([]float64, 3*rm.N)
		iwork := make([]int, rm.N)
		cond := lapack64.Trcon(matrix.CondNorm, rm, work, iwork)
		if cond > matrix.ConditionTolerance {
			return matrix.Condition(cond)
		}
		return nil
	}

	switch {
	case ar == ac:
		if a == b {
			// x = I.
			if ar == 1 {
				m.mat.Data[0] = 1
				return nil
			}
			for i := 0; i < ar; i++ {
				v := m.mat.Data[i*m.mat.Stride : i*m.mat.Stride+ac]
				zero(v)
				v[i] = 1
			}
			return nil
		}
		var lu LU
		lu.Factorize(a)
		return m.SolveLU(&lu, false, b)
	case ar > ac:
		var qr QR
		qr.Factorize(a)
		return m.SolveQR(&qr, false, b)
	default:
		var lq LQ
		lq.Factorize(a)
		return m.SolveLQ(&lq, false, b)
	}
}