/*
* Solve a system of linear equations A*X = B with general M-by-N
* matrix A using the QR factorization computed by DecomposeQRT().
*
* If flags&TRANS != 0:
* find the minimum norm solution of an overdetermined system A.T * X = B.
* i.e min ||X|| s.t A.T*X = B
*
* Otherwise:
* find the least squares solution of an overdetermined system, i.e.,
* solve the least squares problem: min || B - A*X ||.
*
* Arguments:
* B On entry, the right hand side N-by-P matrix B. On exit, the solution matrix X.
*
* A The elements on and above the diagonal contain the min(M,N)-by-N upper
* trapezoidal matrix R. The elements below the diagonal with the matrix 'T',
* represent the ortogonal matrix Q as product of elementary reflectors.
* Matrix A and T are as returned by DecomposeQRT()
*
* T The N-by-N block reflector which, together with trilu(A) represent
* the ortogonal matrix Q as Q = I - Y*T*Y.T where Y = trilu(A).
*
* W Workspace, P-by-nb matrix used for work space in blocked invocations.
*
* flags Indicator flag
*
* nb The block size used in blocked invocations. If nb is zero default
* value N is used.
*
* Compatible with lapack.GELS (the m >= n part)
*/
func SolveQRT(B, A, T, W *matrix.FloatMatrix, flags Flags, nb int) error {
var err error = nil
var R, BT matrix.FloatMatrix
if flags&TRANS != 0 {
// Solve overdetermined system A.T*X = B
// B' = R.-1*B
A.SubMatrix(&R, 0, 0, A.Cols(), A.Cols())
B.SubMatrix(&BT, 0, 0, A.Cols(), B.Cols())
err = SolveTrm(&BT, &R, 1.0, LEFT|UPPER|TRANSA)
// Clear bottom part of B
B.SubMatrix(&BT, A.Cols(), 0)
BT.SetIndexes(0.0)
// X = Q*B'
err = MultQT(B, A, T, W, LEFT, nb)
} else {
// solve least square problem min ||A*X - B||
// B' = Q.T*B
err = MultQT(B, A, T, W, LEFT|TRANS, nb)
if err != nil {
return err
}
// X = R.-1*B'
A.SubMatrix(&R, 0, 0, A.Cols(), A.Cols())
B.SubMatrix(&BT, 0, 0, A.Cols(), B.Cols())
err = SolveTrm(&BT, &R, 1.0, LEFT|UPPER)
}
return err
}
func blockedBuildQ(A, tau, W *matrix.FloatMatrix, nb int) error {
var err error = nil
var ATL, ATR, ABL, ABR, AL matrix.FloatMatrix
var A00, A01, A02, A10, A11, A12, A20, A21, A22 matrix.FloatMatrix
var tT, tB matrix.FloatMatrix
var t0, tau1, t2, Tw, Wrk matrix.FloatMatrix
var mb int
mb = A.Rows() - A.Cols()
Twork := matrix.FloatZeros(nb, nb)
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, mb, 0, pBOTTOMRIGHT)
partition2x1(
&tT,
&tB, tau, 0, pBOTTOM)
// clearing of the columns of the right and setting ABR to unit diagonal
// (only if not applying all reflectors, kb > 0)
for ATL.Rows() > 0 && ATL.Cols() > 0 {
repartition2x2to3x3(&ATL,
&A00, &A01, &A02,
&A10, &A11, &A12,
&A20, &A21, &A22, A, nb, pTOPLEFT)
repartition2x1to3x1(&tT,
&t0,
&tau1,
&t2, tau, nb, pTOP)
// --------------------------------------------------------
// build block reflector from current block
merge2x1(&AL, &A11, &A21)
Twork.SubMatrix(&Tw, 0, 0, A11.Cols(), A11.Cols())
unblkQRBlockReflector(&Tw, &AL, &tau1)
// update with current block reflector (I - Y*T*Y.T)*Atrailing
W.SubMatrix(&Wrk, 0, 0, A12.Cols(), A11.Cols())
updateWithQT(&A12, &A22, &A11, &A21, &Tw, &Wrk, nb, false)
// use unblocked version to compute current block
W.SubMatrix(&Wrk, 0, 0, 1, A11.Cols())
unblockedBuildQ(&AL, &tau1, &Wrk, 0)
// zero upper part
A01.SetIndexes(0.0)
// --------------------------------------------------------
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &A11, &A22, A, pTOPLEFT)
continue3x1to2x1(
&tT,
&tB, &t0, &tau1, tau, pTOP)
}
return err
}
func blkUpperLDL(A, W *matrix.FloatMatrix, p *pPivots, nb int) (err error) {
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, A01, A02, A11, A12, A22 matrix.FloatMatrix
var D1, wrk matrix.FloatMatrix
var pT, pB, p0, p1, p2 pPivots
err = nil
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, 0, 0, pBOTTOMRIGHT)
partitionPivot2x1(
&pT,
&pB, p, 0, pBOTTOM)
for ATL.Rows() > 0 {
repartition2x2to3x3(&ATL,
&A00, &A01, &A02,
nil, &A11, &A12,
nil, nil, &A22, A, nb, pTOPLEFT)
repartPivot2x1to3x1(&pT,
&p0, &p1, &p2 /**/, p, nb, pTOP)
// --------------------------------------------------------
// A11 = LDL(A11)
err = unblkUpperLDL(&A11, &p1)
if err != nil {
return
}
applyColPivots(&A01, &p1, 0, BACKWARD)
applyRowPivots(&A12, &p1, 0, BACKWARD)
scalePivots(&p1, ATL.Rows()-A11.Rows())
A11.Diag(&D1)
// A01 = A01*A11.-T
SolveTrm(&A01, &A11, 1.0, UPPER|UNIT|RIGHT|TRANSA)
// A01 = A01*D1.-1
SolveDiag(&A01, &D1, RIGHT)
// W = D1*U01.T = U01*D1
W.SubMatrix(&wrk, 0, 0, A01.Rows(), nb)
A01.CopyTo(&wrk)
MultDiag(&wrk, &D1, RIGHT)
// A00 = A00 - U01*D1*U01.T = A22 - U01*W.T
UpdateTrm(&A00, &A01, &wrk, -1.0, 1.0, UPPER|TRANSB)
// ---------------------------------------------------------
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &A11, &A22, A, pTOPLEFT)
contPivot3x1to2x1(
&pT,
&pB, &p0, &p1, p, pTOP)
}
return
}
func swapCols(A *matrix.FloatMatrix, src, dst int) {
var c0, c1 matrix.FloatMatrix
if src == dst || A.Rows() == 0 {
return
}
A.SubMatrix(&c0, 0, src, A.Rows(), 1)
A.SubMatrix(&c1, 0, dst, A.Rows(), 1)
Swap(&c0, &c1)
}
func blockedBuildQT(A, T, W *matrix.FloatMatrix, nb int) error {
var err error = nil
var ATL, ATR, ABL, ABR, AL matrix.FloatMatrix
var A00, A01, A11, A12, A21, A22 matrix.FloatMatrix
var TTL, TTR, TBL, TBR matrix.FloatMatrix
var T00, T01, T02, T11, T12, T22 matrix.FloatMatrix
var tau1, Wrk matrix.FloatMatrix
var mb int
mb = A.Rows() - A.Cols()
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, mb, 0, pBOTTOMRIGHT)
partition2x2(
&TTL, &TTR,
&TBL, &TBR, T, 0, 0, pBOTTOMRIGHT)
// clearing of the columns of the right and setting ABR to unit diagonal
// (only if not applying all reflectors, kb > 0)
for ATL.Rows() > 0 && ATL.Cols() > 0 {
repartition2x2to3x3(&ATL,
&A00, &A01, nil,
nil, &A11, &A12,
nil, &A21, &A22, A, nb, pTOPLEFT)
repartition2x2to3x3(&TTL,
&T00, &T01, &T02,
nil, &T11, &T12,
nil, nil, &T22, T, nb, pTOPLEFT)
// --------------------------------------------------------
// update with current block reflector (I - Y*T*Y.T)*Atrailing
W.SubMatrix(&Wrk, 0, 0, A12.Cols(), A11.Cols())
updateWithQT(&A12, &A22, &A11, &A21, &T11, &Wrk, nb, false)
// use unblocked version to compute current block
W.SubMatrix(&Wrk, 0, 0, 1, A11.Cols())
// elementary scalar coefficients on the diagonal, column vector
T11.Diag(&tau1)
merge2x1(&AL, &A11, &A21)
// do an unblocked update to current block
unblockedBuildQ(&AL, &tau1, &Wrk, 0)
// zero upper part
A01.SetIndexes(0.0)
// --------------------------------------------------------
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &A11, &A22, A, pTOPLEFT)
continue3x3to2x2(
&TTL, &TTR,
&TBL, &TBR, &T00, &T11, &T22, T, pTOPLEFT)
}
return err
}
func swapRows(A *matrix.FloatMatrix, src, dst int) {
var r0, r1 matrix.FloatMatrix
if src == dst || A.Rows() == 0 {
return
}
A.SubMatrix(&r0, src, 0, 1, A.Cols())
A.SubMatrix(&r1, dst, 0, 1, A.Cols())
Swap(&r0, &r1)
}
/*
* Compute
* C = C*diag(D) flags & RIGHT == true
* C = diag(D)*C flags & LEFT == true
*
* Arguments
* C M-by-N matrix if flags&RIGHT == true or N-by-M matrix if flags&LEFT == true
*
* D N element column or row vector or N-by-N matrix
*
* flags Indicator bits, LEFT or RIGHT
*/
func MultDiag(C, D *matrix.FloatMatrix, flags Flags) {
var c, d0 matrix.FloatMatrix
if D.Cols() == 1 {
// diagonal is column vector
switch flags & (LEFT | RIGHT) {
case LEFT:
// scale rows; for each column element-wise multiply with D-vector
for k := 0; k < C.Cols(); k++ {
C.SubMatrix(&c, 0, k, C.Rows(), 1)
c.Mul(D)
}
case RIGHT:
// scale columns
for k := 0; k < C.Cols(); k++ {
C.SubMatrix(&c, 0, k, C.Rows(), 1)
// scale the column
c.Scale(D.GetAt(k, 0))
}
}
} else {
// diagonal is row vector
var d *matrix.FloatMatrix
if D.Rows() == 1 {
d = D
} else {
D.SubMatrix(&d0, 0, 0, 1, D.Cols(), D.LeadingIndex()+1)
d = &d0
}
switch flags & (LEFT | RIGHT) {
case LEFT:
for k := 0; k < C.Rows(); k++ {
C.SubMatrix(&c, k, 0, 1, C.Cols())
// scale the row
c.Scale(d.GetAt(0, k))
}
case RIGHT:
// scale columns
for k := 0; k < C.Cols(); k++ {
C.SubMatrix(&c, 0, k, C.Rows(), 1)
// scale the column
c.Scale(d.GetAt(0, k))
}
}
}
}
/*
Continue with 2 by 1 block from 3 by 1 block.
AT A0 AT A0
pBOTTOM: -- <-- A1 ; pTOP: -- <-- --
AB -- AB A1
A2 A2
*/
func continue3x1to2x1(AT, AB, A0, A1, A *matrix.FloatMatrix, pdir pDirection) {
n0 := A0.Rows()
n1 := A1.Rows()
switch pdir {
case pBOTTOM:
A.SubMatrix(AT, 0, 0, n0+n1, A.Cols())
A.SubMatrix(AB, n0+n1, 0, A.Rows()-n0-n1, A.Cols())
case pTOP:
A.SubMatrix(AT, 0, 0, n0, A.Cols())
A.SubMatrix(AB, n0, 0, A.Rows()-n0, A.Cols())
}
}
func blkUpperLDLnoPiv(A, W *matrix.FloatMatrix, nb int) (err error) {
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, A01, A02, A11, A12, A22 matrix.FloatMatrix
var D1, wrk matrix.FloatMatrix
err = nil
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, 0, 0, pBOTTOMRIGHT)
for ATL.Rows() > 0 {
repartition2x2to3x3(&ATL,
&A00, &A01, &A02,
nil, &A11, &A12,
nil, nil, &A22, A, nb, pTOPLEFT)
// --------------------------------------------------------
// A11 = LDL(A11)
unblkUpperLDLnoPiv(&A11)
A11.Diag(&D1)
// A01 = A01*A11.-T
SolveTrm(&A01, &A11, 1.0, UPPER|UNIT|RIGHT|TRANSA)
// A01 = A01*D1.-1
SolveDiag(&A01, &D1, RIGHT)
// W = D1*U01.T = U01*D1
W.SubMatrix(&wrk, 0, 0, A01.Rows(), nb)
A01.CopyTo(&wrk)
MultDiag(&wrk, &D1, RIGHT)
// A00 = A00 - U01*D1*U01.T = A22 - U01*W.T
UpdateTrm(&A00, &A01, &wrk, -1.0, 1.0, UPPER|TRANSB)
// ---------------------------------------------------------
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &A11, &A22, A, pTOPLEFT)
}
return
}
/*
Partition p to 2 by 1 blocks.
AT
A --> --
AB
Parameter nb is initial block size for AT (pTOP) or AB (pBOTTOM).
*/
func partition2x1(AT, AB, A *matrix.FloatMatrix, nb int, side pDirection) {
if nb > A.Rows() {
nb = A.Rows()
}
switch side {
case pTOP:
A.SubMatrix(AT, 0, 0, nb, A.Cols())
A.SubMatrix(AB, nb, 0, A.Rows()-nb, A.Cols())
case pBOTTOM:
A.SubMatrix(AT, 0, 0, A.Rows()-nb, A.Cols())
A.SubMatrix(AB, A.Rows()-nb, 0, nb, A.Cols())
}
}
/*
Partition A to 1 by 2 blocks.
A --> AL | AR
Parameter nb is initial block size for AL (pLEFT) or AR (pRIGHT).
*/
func partition1x2(AL, AR, A *matrix.FloatMatrix, nb int, side pDirection) {
if nb > A.Cols() {
nb = A.Cols()
}
switch side {
case pLEFT:
A.SubMatrix(AL, 0, 0, A.Rows(), nb)
A.SubMatrix(AR, 0, nb, A.Rows(), A.Cols()-nb)
case pRIGHT:
A.SubMatrix(AL, 0, 0, A.Rows(), A.Cols()-nb)
A.SubMatrix(AR, 0, A.Cols()-nb, A.Rows(), nb)
}
}
func row(A *matrix.FloatMatrix, inds ...int) *matrix.FloatMatrix {
var r matrix.FloatMatrix
switch len(inds) {
case 0:
A.SubMatrix(&r, 0, 0, 1, A.Cols())
case 1:
A.SubMatrix(&r, inds[0], 0, 1, A.Cols())
case 2:
A.SubMatrix(&r, inds[0], 0, 1, inds[1])
default:
A.SubMatrix(&r, inds[0], inds[1], 1, inds[2])
}
return &r
}
func col(A *matrix.FloatMatrix, inds ...int) *matrix.FloatMatrix {
var c matrix.FloatMatrix
switch len(inds) {
case 0:
A.SubMatrix(&c, 0, 0, A.Rows(), 1)
case 1:
A.SubMatrix(&c, inds[0], 0, A.Rows(), 1)
case 2:
A.SubMatrix(&c, inds[0], 0, inds[1], 1)
default:
A.SubMatrix(&c, inds[0], inds[1], inds[2], 1)
}
return &c
}
/*
Repartition 1 by 2 blocks to 1 by 3 blocks.
pRIGHT: AL | AR -- A0 A1 | A2
pLEFT: AL | AR <-- A0 | A1 A2
*/
func continue1x3to1x2(AL, AR, A0, A1, A *matrix.FloatMatrix, pdir pDirection) {
k := A0.Cols()
nb := A1.Cols()
switch pdir {
case pRIGHT:
// AL is [A0; A1], AR is A2
A.SubMatrix(AL, 0, 0, A.Rows(), k+nb)
A.SubMatrix(AR, 0, AL.Cols(), A.Rows(), A.Cols()-AL.Cols())
case pLEFT:
// AL is A0; AR is [A1; A2]
A.SubMatrix(AL, 0, 0, A.Rows(), k)
A.SubMatrix(AR, 0, k, A.Rows(), A.Cols()-k)
}
}
/*
* Apply diagonal pivot (row and column swapped) to symmetric matrix blocks.
*
* LOWER triangular; moving from top-left to bottom-right
*
* -----------------------
* | d
* | x P1 x x x P2 -- current row/col 'srcix'
* | x S2 d x x x
* | x S2 x d x x
* | x S2 x x d x
* | x P2 D2 D2 D2 P3 -- swap with row/col 'dstix'
* | x S3 x x x D3 d
* | x S3 x x x D3 x d
* (AR)
*
* UPPER triangular; moving from bottom-right to top-left
*
* d x D3 x x x S3 x |
* d D3 x x x S3 x |
* P3 D2 D2 D2 P2 x | -- dstinx
* d x x S2 x |
* d x S2 x |
* d S2 x |
* P1 x | -- srcinx
* d |
* ----------------------
* (ABR)
*/
func applyBKPivotSym(AR *matrix.FloatMatrix, srcix, dstix int, flags Flags) {
var s, d matrix.FloatMatrix
if flags&LOWER != 0 {
// S2 -- D2
AR.SubMatrix(&s, srcix+1, srcix, dstix-srcix-1, 1)
AR.SubMatrix(&d, dstix, srcix+1, 1, dstix-srcix-1)
Swap(&s, &d)
// S3 -- D3
AR.SubMatrix(&s, dstix+1, srcix, AR.Rows()-dstix-1, 1)
AR.SubMatrix(&d, dstix+1, dstix, AR.Rows()-dstix-1, 1)
Swap(&s, &d)
// swap P1 and P3
p1 := AR.GetAt(srcix, srcix)
p3 := AR.GetAt(dstix, dstix)
AR.SetAt(srcix, srcix, p3)
AR.SetAt(dstix, dstix, p1)
return
}
if flags&UPPER != 0 {
// AL is ATL, AR is ATR; P1 is AL[srcix, srcix];
// S2 -- D2
AR.SubMatrix(&s, dstix+1, srcix, srcix-dstix-1, 1)
AR.SubMatrix(&d, dstix, dstix+1, 1, srcix-dstix-1)
Swap(&s, &d)
// S3 -- D3
AR.SubMatrix(&s, 0, srcix, dstix, 1)
AR.SubMatrix(&d, 0, dstix, dstix, 1)
Swap(&s, &d)
//fmt.Printf("3, AR=%v\n", AR)
// swap P1 and P3
p1 := AR.GetAt(srcix, srcix)
p3 := AR.GetAt(dstix, dstix)
AR.SetAt(srcix, srcix, p3)
AR.SetAt(dstix, dstix, p1)
return
}
}
/*
* Find diagonal pivot and build incrementaly updated block.
*
* (AL) (AR) (WL) (WR)
* -------------------------- ---------- k'th row in W
* x x | c1 w w | k kp1
* x x | c1 d w w | k kp1
* x x | c1 x d w w | k kp1
* x x | c1 x x d w w | k kp1
* x x | c1 r2 r2 r2 r2 w w | k kp1
* x x | c1 x x x r2 d w w | k kp1
* x x | c1 x x x r2 x d w w | k kp1
*
* Matrix AR contains the unfactored part of the matrix and AL the already
* factored columns. Matrix WL is updated values of factored part ie.
* w(i) = l(i)d(i). Matrix WR will have updated values for next column.
* Column WR(k) contains updated AR(c1) and WR(kp1) possible pivot row AR(r2).
*
*
*/
func findAndBuildBKPivotLower(AL, AR, WL, WR *matrix.FloatMatrix, k int) (int, int) {
var r, q int
var rcol, qrow, src, wk, wkp1, wrow matrix.FloatMatrix
// Copy AR column 0 to WR column 0 and update with WL[0:]
AR.SubMatrix(&src, 0, 0, AR.Rows(), 1)
WR.SubMatrix(&wk, 0, 0, AR.Rows(), 1)
src.CopyTo(&wk)
if k > 0 {
WL.SubMatrix(&wrow, 0, 0, 1, WL.Cols())
MVMult(&wk, AL, &wrow, -1.0, 1.0, NOTRANS)
//fmt.Printf("wk after update:\n%v\n", &wk)
}
if AR.Rows() == 1 {
return 0, 1
}
amax := math.Abs(WR.GetAt(0, 0))
// find max off-diagonal on first column.
WR.SubMatrix(&rcol, 1, 0, AR.Rows()-1, 1)
//fmt.Printf("rcol:\n%v\n", &rcol)
// r is row index and rmax is its absolute value
r = IAMax(&rcol) + 1
rmax := math.Abs(rcol.GetAt(r-1, 0))
//fmt.Printf("r=%d, amax=%e, rmax=%e\n", r, amax, rmax)
if amax >= bkALPHA*rmax {
// no pivoting, 1x1 diagonal
return 0, 1
}
// Now we need to copy row r to WR[:,1] and update it
WR.SubMatrix(&wkp1, 0, 1, AR.Rows(), 1)
AR.SubMatrix(&qrow, r, 0, 1, r+1)
qrow.CopyTo(&wkp1)
//fmt.Printf("m(AR)=%d, r=%d, qrow: %v\n", AR.Rows(), r, &qrow)
if r < AR.Rows()-1 {
var wkr matrix.FloatMatrix
AR.SubMatrix(&qrow, r, r, AR.Rows()-r, 1)
wkp1.SubMatrix(&wkr, r, 0, wkp1.Rows()-r, 1)
qrow.CopyTo(&wkr)
//fmt.Printf("m(AR)=%d, r=%d, qrow: %v\n", AR.Rows(), r, &qrow)
}
if k > 0 {
// update wkp1
WL.SubMatrix(&wrow, r, 0, 1, WL.Cols())
//fmt.Printf("initial wpk1:\n%v\n", &wkp1)
MVMult(&wkp1, AL, &wrow, -1.0, 1.0, NOTRANS)
//fmt.Printf("updated wpk1:\n%v\n", &wkp1)
}
// set on-diagonal entry to zero to avoid finding it
p1 := wkp1.GetAt(r, 0)
wkp1.SetAt(r, 0, 0.0)
// max off-diagonal on r'th column/row at index q
q = IAMax(&wkp1)
qmax := math.Abs(wkp1.GetAt(q, 0))
// restore on-diagonal entry
wkp1.SetAt(r, 0, p1)
//arr := math.Abs(WR.GetAt(r, 1))
//fmt.Printf("blk: r=%d, q=%d, amax=%e, rmax=%e, qmax=%e, Arr=%e\n", r, q, amax, rmax, qmax, arr)
if amax >= bkALPHA*rmax*(rmax/qmax) {
// no pivoting, 1x1 diagonal
return 0, 1
}
// if q == r then qmax is not off-diagonal, qmax == WR[r,1] and
// we get 1x1 pivot as following is always true
if math.Abs(WR.GetAt(r, 1)) >= bkALPHA*qmax {
// 1x1 pivoting and interchange with k, r
// pivot row in column WR[:,1] to W[:,0]
//pr := WR.GetAt(r, 1)
//_ = pr
WR.SubMatrix(&src, 0, 1, AR.Rows(), 1)
WR.SubMatrix(&wkp1, 0, 0, AR.Rows(), 1)
src.CopyTo(&wkp1)
wkp1.SetAt(0, 0, src.GetAt(r, 0))
wkp1.SetAt(r, 0, src.GetAt(0, 0))
return r, 1
} else {
// 2x2 pivoting and interchange with k+1, r
return r, 2
}
return 0, 1
}
/*
* Unblocked Bunch-Kauffman LDL factorization.
*
* Corresponds lapack.DSYTF2
*/
func unblkDecompBKUpper(A, wrk *matrix.FloatMatrix, p *pPivots) (error, int) {
var err error
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, a01, A02, a12t, a11, A22, a11inv matrix.FloatMatrix
var cwrk matrix.FloatMatrix
var pT, pB, p0, p1, p2 pPivots
err = nil
nc := 0
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, 0, 0, pBOTTOMRIGHT)
partitionPivot2x1(
&pT,
&pB, p, 0, pBOTTOM)
// permanent working space for symmetric inverse of a11
wrk.SubMatrix(&a11inv, 0, wrk.Cols()-2, 2, 2)
a11inv.SetAt(1, 0, -1.0)
a11inv.SetAt(0, 1, -1.0)
for ATL.Cols() > 0 {
nr := ATL.Rows() - 1
r, np := findBKPivot(&ATL, UPPER)
if r != -1 /*&& r != np-1*/ {
// pivoting needed; do swaping here
//fmt.Printf("pre-pivot ATL [%d]:\n%v\n", ATL.Rows()-np, &ATL)
applyBKPivotSym(&ATL, ATL.Rows()-np, r, UPPER)
if np == 2 {
/*
* [r,r] | [r, nr]
* a11 == --------------- 2-by-2 pivot, swapping [nr-1,nr] and [r,nr]
* [r,0] | [nr,nr]
*/
t := ATL.GetAt(nr-1, nr)
ATL.SetAt(nr-1, nr, ATL.GetAt(r, nr))
ATL.SetAt(r, nr, t)
}
//fmt.Printf("unblk: ATL after %d pivot [r=%d]:\n%v\n", np, r, &ATL)
}
// repartition according the pivot size
repartition2x2to3x3(&ATL,
&A00, &a01, &A02,
nil, &a11, &a12t,
nil, nil, &A22 /**/, A, np, pTOPLEFT)
repartPivot2x1to3x1(&pT,
&p0,
&p1,
&p2 /**/, p, np, pTOP)
// ------------------------------------------------------------
if np == 1 {
// A00 = A00 - a01*a01.T/a11
MVUpdateTrm(&A00, &a01, &a01, -1.0/a11.Float(), UPPER)
// a01 = a01/a11
InvScale(&a01, a11.Float())
if r == -1 {
p1.pivots[0] = ATL.Rows()
} else {
p1.pivots[0] = r + 1
}
} else if np == 2 {
/*
* See comments on unblkDecompBKLower().
*/
a := a11.GetAt(0, 0)
b := a11.GetAt(0, 1)
d := a11.GetAt(1, 1)
a11inv.SetAt(0, 0, d/b)
a11inv.SetAt(1, 1, a/b)
// denominator: (a/b)*(d/b)-1.0 == (a*d - b^2)/b^2
scale := 1.0 / ((a/b)*(d/b) - 1.0)
scale /= b
// cwrk = a21
wrk.SubMatrix(&cwrk, 2, 0, a01.Rows(), a01.Cols())
a01.CopyTo(&cwrk)
//fmt.Printf("cwrk:\n%v\n", &cwrk)
//fmt.Printf("a11inv:\n%v\n", &a11inv)
// a01 = a01*a11.-1
Mult(&a01, &cwrk, &a11inv, scale, 0.0, NOTRANS)
// A00 = A00 - a01*a11.-1*a01.T = A00 - a01*cwrk.T
UpdateTrm(&A00, &a01, &cwrk, -1.0, 1.0, UPPER|TRANSB)
p1.pivots[0] = -(r + 1)
p1.pivots[1] = p1.pivots[0]
}
// ------------------------------------------------------------
nc += np
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &a11, &A22, A, pTOPLEFT)
contPivot3x1to2x1(
&pT,
&pB, &p0, &p1, p, pTOP)
}
return err, nc
}
/*
* Unblocked Bunch-Kauffman LDL factorization.
*
* Corresponds lapack.DSYTF2
*/
func unblkDecompBKLower(A, wrk *matrix.FloatMatrix, p *pPivots) (error, int) {
var err error
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, a10t, a11, A20, a21, A22, a11inv matrix.FloatMatrix
var cwrk matrix.FloatMatrix
var pT, pB, p0, p1, p2 pPivots
err = nil
nc := 0
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, 0, 0, pTOPLEFT)
partitionPivot2x1(
&pT,
&pB, p, 0, pTOP)
// permanent working space for symmetric inverse of a11
wrk.SubMatrix(&a11inv, 0, wrk.Cols()-2, 2, 2)
a11inv.SetAt(1, 0, -1.0)
a11inv.SetAt(0, 1, -1.0)
for ABR.Cols() > 0 {
r, np := findBKPivot(&ABR, LOWER)
if r != 0 && r != np-1 {
// pivoting needed; do swaping here
applyBKPivotSym(&ABR, np-1, r, LOWER)
if np == 2 {
/*
* [0,0] | [r,0]
* a11 == ------------- 2-by-2 pivot, swapping [1,0] and [r,0]
* [r,0] | [r,r]
*/
t := ABR.GetAt(1, 0)
ABR.SetAt(1, 0, ABR.GetAt(r, 0))
ABR.SetAt(r, 0, t)
}
//fmt.Printf("unblk: ABR after %d pivot [r=%d]:\n%v\n", np, r, &ABR)
}
// repartition according the pivot size
repartition2x2to3x3(&ATL,
&A00, nil, nil,
&a10t, &a11, nil,
&A20, &a21, &A22 /**/, A, np, pBOTTOMRIGHT)
repartPivot2x1to3x1(&pT,
&p0,
&p1,
&p2 /**/, p, np, pBOTTOM)
// ------------------------------------------------------------
if np == 1 {
// A22 = A22 - a21*a21.T/a11
MVUpdateTrm(&A22, &a21, &a21, -1.0/a11.Float(), LOWER)
// a21 = a21/a11
InvScale(&a21, a11.Float())
// store pivot point relative to original matrix
p1.pivots[0] = r + ATL.Rows() + 1
} else if np == 2 {
/* from Bunch-Kaufmann 1977:
* (E2 C.T) = ( I2 0 )( E 0 )( I[n-2] E.-1*C.T )
* (C B ) ( C*E.-1 I[n-2] )( 0 A[n-2] )( 0 I2 )
*
* A[n-2] = B - C*E.-1*C.T
*
* E.-1 is inverse of a symmetric matrix, cannot use
* triangular solve. We calculate inverse of 2x2 matrix.
* Following is inspired by lapack.SYTF2
*
* a | b 1 d | -b b d/b | -1
* inv ----- = ------ * ------ = ----------- * --------
* b | d (ad-b^2) -b | a (a*d - b^2) -1 | a/b
*
*/
a := a11.GetAt(0, 0)
b := a11.GetAt(1, 0)
d := a11.GetAt(1, 1)
a11inv.SetAt(0, 0, d/b)
a11inv.SetAt(1, 1, a/b)
// denominator: (a/b)*(d/b)-1.0 == (a*d - b^2)/b^2
scale := 1.0 / ((a/b)*(d/b) - 1.0)
scale /= b
// cwrk = a21
wrk.SubMatrix(&cwrk, 2, 0, a21.Rows(), a21.Cols())
a21.CopyTo(&cwrk)
// a21 = a21*a11.-1
Mult(&a21, &cwrk, &a11inv, scale, 0.0, NOTRANS)
// A22 = A22 - a21*a11.-1*a21.T = A22 - a21*cwrk.T
UpdateTrm(&A22, &a21, &cwrk, -1.0, 1.0, LOWER|TRANSB)
// store pivot point relative to original matrix
p1.pivots[0] = -(r + ATL.Rows() + 1)
p1.pivots[1] = p1.pivots[0]
}
/*
if m(&ABR) < 5 {
var Ablk matrix.FloatMatrix
merge1x2(&Ablk, &ABL, &ABR)
fmt.Printf("unblocked EOL: Ablk r=%d, nc=%d. np=%d\n%v\n", r, nc, np, &Ablk)
}
*/
// ------------------------------------------------------------
nc += np
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &a11, &A22, A, pBOTTOMRIGHT)
contPivot3x1to2x1(
&pT,
&pB, &p0, &p1, p, pBOTTOM)
}
return err, nc
}
func findBKPivot(A *matrix.FloatMatrix, flags Flags) (int, int) {
var r, q int
var rcol, qrow matrix.FloatMatrix
if flags&LOWER != 0 {
if A.Rows() == 1 {
return 0, 1
}
amax := math.Abs(A.GetAt(0, 0))
// column below diagonal at [0, 0]
A.SubMatrix(&rcol, 1, 0, A.Rows()-1, 1)
r = IAMax(&rcol) + 1
// max off-diagonal on first column at index r
rmax := math.Abs(A.GetAt(r, 0))
//fmt.Printf("m(A)=%d, r=%d, rmax=%e, amax=%e\n", m(A), r, rmax, amax)
if amax >= bkALPHA*rmax {
// no pivoting, 1x1 diagonal
return 0, 1
}
// max off-diagonal on r'th row at index q
A.SubMatrix(&qrow, r, 0, 1, r /*+1*/)
q = IAMax(&qrow)
qmax := math.Abs(A.GetAt(r, q /*+1*/))
if r < A.Rows()-1 {
// rest of the r'th row after diagonal
A.SubMatrix(&qrow, r+1, r, A.Rows()-r-1, 1)
q = IAMax(&qrow)
//fmt.Printf("qrow: %d, q: %d\n", qrow.NumElements(), q)
qmax2 := math.Abs(qrow.GetAt(q, 0))
if qmax2 > qmax {
qmax = qmax2
}
}
//fmt.Printf("m(A)=%d: q=%d, qmax=%e %v\n", m(A), q, qmax, &qrow)
//arr := math.Abs(A.GetAt(r, r))
//fmt.Printf("unblk: r=%d, q=%d, amax=%e, rmax=%e, qmax=%e, Arr=%e\n", r, q, amax, rmax, qmax, arr)
if amax >= bkALPHA*rmax*(rmax/qmax) {
// no pivoting, 1x1 diagonal
return 0, 1
}
if math.Abs(A.GetAt(r, r)) >= bkALPHA*qmax {
// 1x1 pivoting and interchange with k, r
return r, 1
} else {
// 2x2 pivoting and interchange with k+1, r
return r, 2
}
}
if flags&UPPER != 0 {
if A.Rows() == 1 {
return 0, 1
}
//fmt.Printf("upper A:\n%v\n", A)
lastcol := A.Rows() - 1
amax := math.Abs(A.GetAt(lastcol, lastcol))
// column above [A.Rows()-1, A.Rows()-1]
A.SubMatrix(&rcol, 0, lastcol, lastcol, 1)
r = IAMax(&rcol)
// max off-diagonal on first column at index r
rmax := math.Abs(A.GetAt(r, lastcol))
//fmt.Printf("m(A)=%d, r=%d, rmax=%e, amax=%e\n", m(A), r, rmax, amax)
if amax >= bkALPHA*rmax {
// no pivoting, 1x1 diagonal
return -1, 1
}
// max off-diagonal on r'th row at index q
// a) rest of the r'th row above diagonal
qmax := 0.0
if r > 0 {
A.SubMatrix(&qrow, 0, r, r, 1)
q = IAMax(&qrow)
qmax = math.Abs(A.GetAt(q, r /*+1*/))
}
// b) elements right of diagonal
A.SubMatrix(&qrow, r, r+1, 1, lastcol-r)
q = IAMax(&qrow)
//fmt.Printf("qrow: %d, q: %d, data: %v\n", qrow.NumElements(), q, &qrow)
qmax2 := math.Abs(qrow.GetAt(0, q))
if qmax2 > qmax {
qmax = qmax2
}
//fmt.Printf("m(A)=%d: q=%d, qmax=%e %v\n", m(A), q, qmax, &qrow)
//fmt.Printf("unblk: r=%d, q=%d, amax=%e, rmax=%e, qmax=%e\n", r, q, amax, rmax, qmax)
if amax >= bkALPHA*rmax*(rmax/qmax) {
// no pivoting, 1x1 diagonal
return -1, 1
}
if math.Abs(A.GetAt(r, r)) >= bkALPHA*qmax {
// 1x1 pivoting and interchange with k, r
return r, 1
} else {
// 2x2 pivoting and interchange with k+1, r
return r, 2
}
}
return 0, 1
}
/*
* Apply diagonal pivot (row and column swapped) to symmetric matrix blocks.
* AR[0,0] is on diagonal and AL is block to the left of diagonal and AR the
* triangular diagonal block. Need to swap row and column.
*
* LOWER triangular; moving from top-left to bottom-right
*
* d
* x d
* x x d |
* --------------------------
* S1 S1 S1 | P1 x x x P2 -- current row
* x x x | S2 d x x x
* x x x | S2 x d x x
* x x x | S2 x x d x
* D1 D1 D1 | P2 D2 D2 D2 P3 -- swap with row 'index'
* x x x | S3 x x x D3 d
* x x x | S3 x x x D3 x d
* (ABL) (ABR)
*
* UPPER triangular; moving from bottom-right to top-left
*
* (ATL) (ATR)
* d x x D3 x x x | S3 x x
* d x D3 x x x | S3 x x
* d D3 x x x | S3 x x
* P3 D2 D2 D2| P2 D1 D1
* d x x | S2 x x
* d x | S2 x x
* d | S2 x x
* -----------------------------
* | P1 S1 S1
* | d x
* | d
* (ABR)
*/
func applyPivotSym(AL, AR *matrix.FloatMatrix, index int, flags Flags) {
var s, d matrix.FloatMatrix
if flags&LOWER != 0 {
// AL is [ABL]; AR is [ABR]; P1 is AR[0,0], P2 is AR[index, 0]
// S1 -- D1
AL.SubMatrix(&s, 0, 0, 1, AL.Cols())
AL.SubMatrix(&d, index, 0, 1, AL.Cols())
Swap(&s, &d)
// S2 -- D2
AR.SubMatrix(&s, 1, 0, index-1, 1)
AR.SubMatrix(&d, index, 1, 1, index-1)
Swap(&s, &d)
// S3 -- D3
AR.SubMatrix(&s, index+1, 0, AR.Rows()-index-1, 1)
AR.SubMatrix(&d, index+1, index, AR.Rows()-index-1, 1)
Swap(&s, &d)
// swap P1 and P3
p1 := AR.GetAt(0, 0)
p3 := AR.GetAt(index, index)
AR.SetAt(0, 0, p3)
AR.SetAt(index, index, p1)
return
}
if flags&UPPER != 0 {
// AL is merged from [ATL, ATR], AR is [ABR]; P1 is AR[0, 0]; P2 is AL[index, -1]
colno := AL.Cols() - AR.Cols()
// S1 -- D1; S1 is on the first row of AR
AR.SubMatrix(&s, 0, 1, 1, AR.Cols()-1)
AL.SubMatrix(&d, index, colno+1, 1, s.Cols())
Swap(&s, &d)
// S2 -- D2
AL.SubMatrix(&s, index+1, colno, AL.Rows()-index-2, 1)
AL.SubMatrix(&d, index, index+1, 1, colno-index-1)
Swap(&s, &d)
// S3 -- D3
AL.SubMatrix(&s, 0, index, index, 1)
AL.SubMatrix(&d, 0, colno, index, 1)
Swap(&s, &d)
//fmt.Printf("3, AR=%v\n", AR)
// swap P1 and P3
p1 := AR.GetAt(0, 0)
p3 := AL.GetAt(index, index)
AR.SetAt(0, 0, p3)
AL.SetAt(index, index, p1)
return
}
}
func unblkBoundedBKUpper(A, wrk *matrix.FloatMatrix, p *pPivots, ncol int) (error, int) {
var err error
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, a01, A02, a11, a12t, A22, a11inv matrix.FloatMatrix
var w00, w01, w11 matrix.FloatMatrix
var cwrk matrix.FloatMatrix
var wx, Ax, wz matrix.FloatMatrix
var pT, pB, p0, p1, p2 pPivots
err = nil
nc := 0
if ncol > A.Cols() {
ncol = A.Cols()
}
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, 0, 0, pBOTTOMRIGHT)
partitionPivot2x1(
&pT,
&pB, p, 0, pBOTTOM)
// permanent working space for symmetric inverse of a11
wrk.SubMatrix(&a11inv, wrk.Rows()-2, 0, 2, 2)
a11inv.SetAt(0, 1, -1.0)
a11inv.SetAt(1, 0, -1.0)
for ATL.Cols() > 0 && nc < ncol {
partition2x2(
&w00, &w01,
nil, &w11, wrk, nc, nc, pBOTTOMRIGHT)
merge1x2(&wx, &w00, &w01)
merge1x2(&Ax, &ATL, &ATR)
//fmt.Printf("ATL:\n%v\n", &ATL)
r, np := findAndBuildBKPivotUpper(&ATL, &ATR, &w00, &w01, nc)
//fmt.Printf("[w00;w01]:\n%v\n", &wx)
//fmt.Printf("after find: r=%d, np=%d, ncol=%d, nc=%d\n", r, np, ncol, nc)
w00.SubMatrix(&wz, 0, w00.Cols()-2, w00.Rows(), 2)
if np > ncol-nc {
// next pivot does not fit into ncol columns, restore last column,
// return with number of factorized columns
return err, nc
}
if r != -1 {
// pivoting needed; np == 1, last row; np == 2; next to last rows
nrow := ATL.Rows() - np
applyBKPivotSym(&ATL, nrow, r, UPPER)
// swap left hand rows to get correct updates
swapRows(&ATR, nrow, r)
swapRows(&w01, nrow, r)
if np == 2 {
/* pivot block on diagonal; -1,-1
* [r, r] | [r ,-1]
* ---------------- 2-by-2 pivot, swapping [1,0] and [r,0]
* [r,-1] | [-1,-1]
*/
t0 := w00.GetAt(-2, -1)
tr := w00.GetAt(r, -1)
//fmt.Printf("nc=%d, t0=%e, tr=%e\n", nc, t0, tr)
w00.SetAt(-2, -1, tr)
w00.SetAt(r, -1, t0)
// interchange diagonal entries on w11[:,1]
t0 = w00.GetAt(-2, -2)
tr = w00.GetAt(r, -2)
w00.SetAt(-2, -2, tr)
w00.SetAt(r, -2, t0)
//fmt.Printf("wrk:\n%v\n", &wz)
}
//fmt.Printf("pivoted A:\n%v\n", &Ax)
//fmt.Printf("pivoted wrk:\n%v\n", &wx)
}
// repartition according the pivot size
repartition2x2to3x3(&ATL,
&A00, &a01, &A02,
nil, &a11, &a12t,
nil, nil, &A22 /**/, A, np, pTOPLEFT)
repartPivot2x1to3x1(&pT,
&p0,
&p1,
&p2 /**/, p, np, pTOP)
// ------------------------------------------------------------
wlc := w00.Cols() - np
//wlr := w00.Rows() - 1
w00.SubMatrix(&cwrk, 0, wlc, a01.Rows(), np)
if np == 1 {
//fmt.Printf("wz:\n%v\n", &wz)
//fmt.Printf("a11 <-- %e\n", w00.GetAt(a01.Rows(), wlc))
//w00.SubMatrix(&cwrk, 0, wlc-np+1, a01.Rows(), np)
a11.SetAt(0, 0, w00.GetAt(a01.Rows(), wlc))
// a21 = a21/a11
//fmt.Printf("np == 1: pre-update a01\n%v\n", &a01)
cwrk.CopyTo(&a01)
InvScale(&a01, a11.Float())
//fmt.Printf("np == 1: cwrk\n%v\na21\n%v\n", &cwrk, &a21)
// store pivot point relative to original matrix
if r == -1 {
p1.pivots[0] = ATL.Rows()
} else {
p1.pivots[0] = r + 1
}
} else if np == 2 {
/* d | b
* w00 == ------
* . | a
*/
a := w00.GetAt(-1, -1)
b := w00.GetAt(-2, -1)
d := w00.GetAt(-2, -2)
a11inv.SetAt(1, 1, d/b)
a11inv.SetAt(0, 0, a/b)
// denominator: (a/b)*(d/b)-1.0 == (a*d - b^2)/b^2
scale := 1.0 / ((a/b)*(d/b) - 1.0)
scale /= b
//fmt.Printf("a11inv:\n%v\n", &a11inv)
// a01 = a01*a11.-1
Mult(&a01, &cwrk, &a11inv, scale, 0.0, NOTRANS)
a11.SetAt(1, 1, a)
a11.SetAt(0, 1, b)
a11.SetAt(0, 0, d)
// store pivot point relative to original matrix
p1.pivots[0] = -(r + 1)
p1.pivots[1] = p1.pivots[0]
}
//fmt.Printf("end-of-loop: Ax r=%d, nc=%d. np=%d\n%v\n", r, nc, np, &Ax)
//fmt.Printf("wx m(wblk)=%d:\n%v\n", m(&wx), &wx)
// ------------------------------------------------------------
nc += np
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &a11, &A22, A, pTOPLEFT)
contPivot3x1to2x1(
&pT,
&pB, &p0, &p1, p, pTOP)
}
return err, nc
}
func blkDecompBKLower(A, W *matrix.FloatMatrix, p *pPivots, nb int) (err error) {
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, A10, A11, A20, A21, A22 matrix.FloatMatrix
var wrk matrix.FloatMatrix
var pT, pB, p0, p1, p2 pPivots
var nblk int = 0
err = nil
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, 0, 0, pTOPLEFT)
partitionPivot2x1(
&pT,
&pB, p, 0, pTOP)
for ABR.Cols() >= nb {
err, nblk = unblkBoundedBKLower(&ABR, W, &pB, nb)
// repartition nblk size
repartition2x2to3x3(&ATL,
&A00, nil, nil,
&A10, &A11, nil,
&A20, &A21, &A22, A, nblk, pBOTTOMRIGHT)
repartPivot2x1to3x1(&pT,
&p0, &p1, &p2 /**/, p, nblk, pBOTTOM)
// --------------------------------------------------------
// here [A11;A21] has been decomposed by unblkBoundedBKLower()
// Now we need update A22
// wrk is original A21
W.SubMatrix(&wrk, nblk, 0, A21.Rows(), nblk)
// A22 = A22 - L21*D1*L21.T = A22 - L21*W.T
UpdateTrm(&A22, &A21, &wrk, -1.0, 1.0, LOWER|TRANSB)
// partially undo row pivots left of diagonal
for k := nblk; k > 0; k-- {
var s, d matrix.FloatMatrix
r := p1.pivots[k-1]
rlen := k - 1
if r < 0 {
r = -r
rlen--
}
if r == k {
// no pivot
continue
}
ABR.SubMatrix(&s, k-1, 0, 1, rlen)
ABR.SubMatrix(&d, r-1, 0, 1, rlen)
Swap(&d, &s)
if p1.pivots[k-1] < 0 {
k-- // skip other entry in 2x2 pivots
}
}
// shift pivot values
for k, n := range p1.pivots {
if n > 0 {
p1.pivots[k] += ATL.Rows()
} else {
p1.pivots[k] -= ATL.Rows()
}
}
// zero work for debuging
W.Scale(0.0)
// ---------------------------------------------------------
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &A11, &A22, A, pBOTTOMRIGHT)
contPivot3x1to2x1(
&pT,
&pB, &p0, &p1, p, pBOTTOM)
}
// do the last part with unblocked code
if ABR.Cols() > 0 {
unblkDecompBKLower(&ABR, W, &pB)
// shift pivot values
for k, n := range pB.pivots {
if n > 0 {
pB.pivots[k] += ATL.Rows()
} else {
pB.pivots[k] -= ATL.Rows()
}
}
}
return
}
/*
* ( A11 A12 ) ( L11 0 )( D1 0 )( L11.t L21.t )
* ( A21 A22 ) ( L21 L22 )( 0 D2 )( 0 L22.t )
*
* A11 = L11*D1*L11.t -> L11\D1 = LDL(A11)
* A12 = L11*D1*L21.t
* A21 = L21*D1*L11.t => L21 = A21*(D1*L11.t).-1 = A21*L11.-T*D1.-1
* A22 = L21*D1*L21.t + L22*D2*L22.t => L22 = A22 - L21*D1*L21.t
*/
func blkLowerLDL(A, W *matrix.FloatMatrix, p *pPivots, nb int) (err error) {
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, A10, A11, A20, A21, A22 matrix.FloatMatrix
var /*D1,*/ wrk matrix.FloatMatrix
var pT, pB, p0, p1, p2 pPivots
var nblk int
err = nil
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, 0, 0, pTOPLEFT)
partitionPivot2x1(
&pT,
&pB, p, 0, pTOP)
for ABR.Cols() > nb {
err, nblk = unblkBoundedLowerLDL(&ABR, W, &pB, nb)
repartition2x2to3x3(&ATL,
&A00, nil, nil,
&A10, &A11, nil,
&A20, &A21, &A22, A, nblk, pBOTTOMRIGHT)
repartPivot2x1to3x1(&pT,
&p0, &p1, &p2 /**/, p, nblk, pBOTTOM)
// --------------------------------------------------------
// wrk = D1*L21.T
W.SubMatrix(&wrk, nblk, 0, A21.Rows(), nblk)
// A22 = A22 - L21*D1*L21.T = A22 - L21*wrk.T
UpdateTrm(&A22, &A21, &wrk, -1.0, 1.0, LOWER|TRANSB)
applyRowPivots(&ABL, &p1, 0, FORWARD)
scalePivots(&p1, ATL.Rows())
//var Ablk matrix.FloatMatrix
//merge1x2(&Ablk, &ABL, &ABR)
//fmt.Printf("blk nblk=%d, Ablk:\n%v\n", nblk, &Ablk)
// ---------------------------------------------------------
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &A11, &A22, A, pBOTTOMRIGHT)
contPivot3x1to2x1(
&pT,
&pB, &p0, &p1, p, pBOTTOM)
}
if ABR.Cols() > 0 {
// A11 = LDL(A11)
err = unblkLowerLDL(&ABR, &pB)
if err != nil {
return
}
//fmt.Printf("unblk pivots: %v\n", pB.pivots)
applyRowPivots(&ABL, &pB, 0, FORWARD)
scalePivots(&pB, ATL.Rows())
}
return
}
// Build Q in place by applying elementary reflectors in reverse order to
// an implied identity matrix. This forms Q = H(1)H(2) ... H(k)
//
// this is compatibe with lapack.DORG2R
func unblockedBuildQ(A, tau, w *matrix.FloatMatrix, kb int) error {
var err error = nil
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, a01, A02, a10t, a11, a12t, A20, a21, A22 matrix.FloatMatrix
var tT, tB matrix.FloatMatrix
var t0, tau1, t2, w1 matrix.FloatMatrix
var mb int
var rowvec bool
mb = A.Rows() - A.Cols()
rowvec = tau.Rows() == 1
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, mb, 0, pBOTTOMRIGHT)
if rowvec {
partition1x2(
&tT, &tB, tau, 0, pRIGHT)
} else {
partition2x1(
&tT,
&tB, tau, 0, pBOTTOM)
}
// clearing of the columns of the right and setting ABR to unit diagonal
// (only if not applying all reflectors, kb > 0)
for ATL.Rows() > 0 && ATL.Cols() > 0 {
repartition2x2to3x3(&ATL,
&A00, &a01, &A02,
&a10t, &a11, &a12t,
&A20, &a21, &A22, A, 1, pTOPLEFT)
if rowvec {
repartition1x2to1x3(&tT,
&t0, &tau1, &t2, tau, 1, pLEFT)
} else {
repartition2x1to3x1(&tT,
&t0,
&tau1,
&t2, tau, 1, pTOP)
}
// --------------------------------------------------------
// adjust workspace to correct size
w.SubMatrix(&w1, 0, 0, 1, a12t.Cols())
// apply Householder reflection from left
applyHHTo2x1(&tau1, &a21, &a12t, &A22, &w1, LEFT)
// apply (in-place) current elementary reflector to unit vector
a21.Scale(-tau1.Float())
a11.SetAt(0, 0, 1.0-tau1.Float())
// zero the upper part
a01.SetIndexes(0.0)
// --------------------------------------------------------
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &a11, &A22, A, pTOPLEFT)
if rowvec {
continue1x3to1x2(
&tT, &tB, &t0, &tau1, tau, pLEFT)
} else {
continue3x1to2x1(
&tT,
&tB, &t0, &tau1, tau, pTOP)
}
}
return err
}
/*
* Unblocked, bounded Bunch-Kauffman LDL factorization for at most ncol columns.
* At most ncol columns are factorized and trailing matrix updates are restricted
* to ncol columns. Also original columns are accumulated to working matrix, which
* is used by calling blocked algorithm to update the trailing matrix with BLAS3
* update.
*
* Corresponds lapack.DLASYF
*/
func unblkBoundedBKLower(A, wrk *matrix.FloatMatrix, p *pPivots, ncol int) (error, int) {
var err error
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, a10t, a11, A20, a21, A22, a11inv matrix.FloatMatrix
var w00, w10, w11 matrix.FloatMatrix
var cwrk matrix.FloatMatrix
//var s, d matrix.FloatMatrix
var pT, pB, p0, p1, p2 pPivots
err = nil
nc := 0
if ncol > A.Cols() {
ncol = A.Cols()
}
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, 0, 0, pTOPLEFT)
partitionPivot2x1(
&pT,
&pB, p, 0, pTOP)
// permanent working space for symmetric inverse of a11
wrk.SubMatrix(&a11inv, 0, wrk.Cols()-2, 2, 2)
a11inv.SetAt(1, 0, -1.0)
a11inv.SetAt(0, 1, -1.0)
for ABR.Cols() > 0 && nc < ncol {
partition2x2(
&w00, nil,
&w10, &w11, wrk, nc, nc, pTOPLEFT)
//fmt.Printf("ABR:\n%v\n", &ABR)
r, np := findAndBuildBKPivotLower(&ABL, &ABR, &w10, &w11, nc)
//fmt.Printf("after find: r=%d, np=%d, ncol=%d, nc=%d\n", r, np, ncol, nc)
if np > ncol-nc {
// next pivot does not fit into ncol columns, restore last column,
// return with number of factorized columns
//fmt.Printf("np > ncol-nc: %d > %d\n", np, ncol-nc)
return err, nc
//goto undo
}
if r != 0 && r != np-1 {
// pivoting needed; do swaping here
applyBKPivotSym(&ABR, np-1, r, LOWER)
// swap left hand rows to get correct updates
swapRows(&ABL, np-1, r)
swapRows(&w10, np-1, r)
//ABL.SubMatrix(&s, np-1, 0, 1, ABL.Cols())
//ABL.SubMatrix(&d, r, 0, 1, ABL.Cols())
//Swap(&s, &d)
//w10.SubMatrix(&s, np-1, 0, 1, w10.Cols())
//w10.SubMatrix(&d, r, 0, 1, w10.Cols())
//Swap(&s, &d)
if np == 2 {
/*
* [0,0] | [r,0]
* a11 == ------------- 2-by-2 pivot, swapping [1,0] and [r,0]
* [r,0] | [r,r]
*/
t0 := w11.GetAt(1, 0)
tr := w11.GetAt(r, 0)
//fmt.Printf("nc=%d, t0=%e, tr=%e\n", nc, t0, tr)
w11.SetAt(1, 0, tr)
w11.SetAt(r, 0, t0)
// interchange diagonal entries on w11[:,1]
t0 = w11.GetAt(1, 1)
tr = w11.GetAt(r, 1)
w11.SetAt(1, 1, tr)
w11.SetAt(r, 1, t0)
}
//fmt.Printf("pivoted A:\n%v\n", A)
//fmt.Printf("pivoted wrk:\n%v\n", wrk)
}
// repartition according the pivot size
repartition2x2to3x3(&ATL,
&A00, nil, nil,
&a10t, &a11, nil,
&A20, &a21, &A22 /**/, A, np, pBOTTOMRIGHT)
repartPivot2x1to3x1(&pT,
&p0,
&p1,
&p2 /**/, p, np, pBOTTOM)
// ------------------------------------------------------------
if np == 1 {
//
w11.SubMatrix(&cwrk, np, 0, a21.Rows(), np)
a11.SetAt(0, 0, w11.GetAt(0, 0))
// a21 = a21/a11
//fmt.Printf("np == 1: pre-update a21\n%v\n", &a21)
cwrk.CopyTo(&a21)
InvScale(&a21, a11.Float())
//fmt.Printf("np == 1: cwrk\n%v\na21\n%v\n", &cwrk, &a21)
// store pivot point relative to original matrix
p1.pivots[0] = r + ATL.Rows() + 1
} else if np == 2 {
/*
* See comments for this block in unblkDecompBKLower().
*/
a := w11.GetAt(0, 0)
b := w11.GetAt(1, 0)
d := w11.GetAt(1, 1)
a11inv.SetAt(0, 0, d/b)
a11inv.SetAt(1, 1, a/b)
// denominator: (a/b)*(d/b)-1.0 == (a*d - b^2)/b^2
scale := 1.0 / ((a/b)*(d/b) - 1.0)
scale /= b
w11.SubMatrix(&cwrk, np, 0, a21.Rows(), np)
// a21 = a21*a11.-1
Mult(&a21, &cwrk, &a11inv, scale, 0.0, NOTRANS)
a11.SetAt(0, 0, a)
a11.SetAt(1, 0, b)
a11.SetAt(1, 1, d)
// store pivot point relative to original matrix
p1.pivots[0] = -(r + ATL.Rows() + 1)
p1.pivots[1] = p1.pivots[0]
}
/*
if m(&ABR) < 5 {
var Ablk, wblk, w5 matrix.FloatMatrix
merge1x2(&Ablk, &ABL, &ABR)
merge1x2(&wblk, &w10, &w11)
wblk.SubMatrix(&w5, 0, 0, Ablk.Rows(), wblk.Cols())
fmt.Printf("blocked EOL: Ablk r=%d, nc=%d. np=%d\n%v\n", r, nc, np, &Ablk)
fmt.Printf("wblk m(wblk)=%d:\n%v\n", m(&w5), &w5)
}
*/
// ------------------------------------------------------------
nc += np
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &a11, &A22, A, pBOTTOMRIGHT)
contPivot3x1to2x1(
&pT,
&pB, &p0, &p1, p, pBOTTOM)
}
// undo applied partial row pivots (AL, w00)
//undo:
return err, nc
}
func findAndBuildPivot(AL, AR, WL, WR *matrix.FloatMatrix, k int) int {
var dg, acol, wcol, wrow matrix.FloatMatrix
// updated diagonal values on last column of workspace
WR.SubMatrix(&dg, 0, WR.Cols()-1, AR.Rows(), 1)
// find on-diagonal maximun value
dmax := IAMax(&dg)
//fmt.Printf("dmax=%d, val=%e\n", dmax, dg.GetAt(dmax, 0))
// copy to first column of WR and update with factorized columns
WR.SubMatrix(&wcol, 0, 0, WR.Rows(), 1)
if dmax == 0 {
AR.SubMatrix(&acol, 0, 0, AR.Rows(), 1)
acol.CopyTo(&wcol)
} else {
AR.SubMatrix(&acol, dmax, 0, 1, dmax+1)
acol.CopyTo(&wcol)
if dmax < AR.Rows()-1 {
var wrst matrix.FloatMatrix
WR.SubMatrix(&wrst, dmax, 0, wcol.Rows()-dmax, 1)
AR.SubMatrix(&acol, dmax, dmax, AR.Rows()-dmax, 1)
acol.CopyTo(&wrst)
}
}
if k > 0 {
WL.SubMatrix(&wrow, dmax, 0, 1, WL.Cols())
//fmt.Printf("update with wrow:%v\n", &wrow)
//fmt.Printf("update wcol\n%v\n", &wcol)
MVMult(&wcol, AL, &wrow, -1.0, 1.0, NOTRANS)
//fmt.Printf("updated wcol:\n%v\n", &wcol)
}
if dmax > 0 {
// pivot column in workspace
t0 := WR.GetAt(0, 0)
WR.SetAt(0, 0, WR.GetAt(dmax, 0))
WR.SetAt(dmax, 0, t0)
// pivot on diagonal
t0 = dg.GetAt(0, 0)
dg.SetAt(0, 0, dg.GetAt(dmax, 0))
dg.SetAt(dmax, 0, t0)
}
return dmax
}
func findAndBuildBKPivotUpper(AL, AR, WL, WR *matrix.FloatMatrix, k int) (int, int) {
var r, q int
var rcol, qrow, src, wk, wkp1, wrow matrix.FloatMatrix
lc := AL.Cols() - 1
wc := WL.Cols() - 1
lr := AL.Rows() - 1
// Copy AR[:,lc] to WR[:,wc] and update with WL[0:]
AL.SubMatrix(&src, 0, lc, AL.Rows(), 1)
WL.SubMatrix(&wk, 0, wc, AL.Rows(), 1)
src.CopyTo(&wk)
if k > 0 {
WR.SubMatrix(&wrow, lr, 0, 1, WR.Cols())
//fmt.Printf("wrow: %v\n", &wrow)
MVMult(&wk, AR, &wrow, -1.0, 1.0, NOTRANS)
//fmt.Printf("wk after update:\n%v\n", &wk)
}
if AL.Rows() == 1 {
return -1, 1
}
amax := math.Abs(WL.GetAt(lr, wc))
// find max off-diagonal on first column.
WL.SubMatrix(&rcol, 0, wc, lr, 1)
//fmt.Printf("rcol:\n%v\n", &rcol)
// r is row index and rmax is its absolute value
r = IAMax(&rcol)
rmax := math.Abs(rcol.GetAt(r, 0))
//fmt.Printf("r=%d, amax=%e, rmax=%e\n", r, amax, rmax)
if amax >= bkALPHA*rmax {
// no pivoting, 1x1 diagonal
return -1, 1
}
// Now we need to copy row r to WR[:,wc-1] and update it
WL.SubMatrix(&wkp1, 0, wc-1, AL.Rows(), 1)
if r > 0 {
// above the diagonal part of AL
AL.SubMatrix(&qrow, 0, r, r, 1)
qrow.CopyTo(&wkp1)
}
//fmt.Printf("m(AR)=%d, r=%d, qrow: %v\n", AL.Rows(), r, &qrow)
var wkr matrix.FloatMatrix
AL.SubMatrix(&qrow, r, r, 1, AL.Rows()-r)
wkp1.SubMatrix(&wkr, r, 0, AL.Rows()-r, 1)
qrow.CopyTo(&wkr)
//fmt.Printf("m(AR)=%d, r=%d, qrow: %v\n", AR.Rows(), r, &qrow)
if k > 0 {
// update wkp1
WR.SubMatrix(&wrow, r, 0, 1, WR.Cols())
//fmt.Printf("initial wpk1:\n%v\n", &wkp1)
MVMult(&wkp1, AR, &wrow, -1.0, 1.0, NOTRANS)
}
//fmt.Printf("updated wpk1:\n%v\n", &wkp1)
// set on-diagonal entry to zero to avoid hitting it.
p1 := wkp1.GetAt(r, 0)
wkp1.SetAt(r, 0, 0.0)
// max off-diagonal on r'th column/row at index q
q = IAMax(&wkp1)
qmax := math.Abs(wkp1.GetAt(q, 0))
wkp1.SetAt(r, 0, p1)
//fmt.Printf("blk: r=%d, q=%d, amax=%e, rmax=%e, qmax=%e\n", r, q, amax, rmax, qmax)
if amax >= bkALPHA*rmax*(rmax/qmax) {
// no pivoting, 1x1 diagonal
return -1, 1
}
// if q == r then qmax is not off-diagonal, qmax == WR[r,1] and
// we get 1x1 pivot as following is always true
if math.Abs(WL.GetAt(r, wc-1)) >= bkALPHA*qmax {
// 1x1 pivoting and interchange with k, r
// pivot row in column WR[:,1] to W[:,0]
//p1 := WL.GetAt(r, wc-1)
WL.SubMatrix(&src, 0, wc-1, AL.Rows(), 1)
WL.SubMatrix(&wkp1, 0, wc, AL.Rows(), 1)
src.CopyTo(&wkp1)
wkp1.SetAt(-1, 0, src.GetAt(r, 0))
wkp1.SetAt(r, 0, src.GetAt(-1, 0))
return r, 1
} else {
// 2x2 pivoting and interchange with k+1, r
return r, 2
}
return -1, 1
}
func blkDecompBKUpper(A, W *matrix.FloatMatrix, p *pPivots, nb int) (err error) {
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, A01, A02, A11, A12, A22 matrix.FloatMatrix
var wrk matrix.FloatMatrix
var pT, pB, p0, p1, p2 pPivots
var nblk int = 0
err = nil
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, 0, 0, pBOTTOMRIGHT)
partitionPivot2x1(
&pT,
&pB, p, 0, pBOTTOM)
for ATL.Cols() >= nb {
err, nblk = unblkBoundedBKUpper(&ATL, W, &pT, nb)
// repartition nblk size
repartition2x2to3x3(&ATL,
&A00, &A01, &A02,
nil, &A11, &A12,
nil, nil, &A22, A, nblk, pTOPLEFT)
repartPivot2x1to3x1(&pT,
&p0, &p1, &p2 /**/, p, nblk, pTOP)
// --------------------------------------------------------
// here [A01;A11] has been decomposed by unblkBoundedBKUpper()
// Now we need update A00
// wrk is original A01; D1*L01.T
W.SubMatrix(&wrk, 0, W.Cols()-nblk, A01.Rows(), nblk)
// A00 = A00 - L01*D1*L01.T = A00 - L01*W.T
UpdateTrm(&A00, &A01, &wrk, -1.0, 1.0, UPPER|TRANSB)
// partially undo row pivots right of diagonal
for k := 0; k < nblk; k++ {
var s, d matrix.FloatMatrix
r := p1.pivots[k]
colno := A00.Cols() + k
np := 1
if r < 0 {
r = -r
np = 2
}
rlen := ATL.Cols() - colno - np
//fmt.Printf("undo: k=%d, r=%d, colno=%d, rlen=%d\n", k, r, colno, rlen)
if r == colno+1 {
// no pivot
continue
}
ATL.SubMatrix(&s, colno, colno+np, 1, rlen)
ATL.SubMatrix(&d, r-1, colno+np, 1, rlen)
//fmt.Printf("s %d: %v\n", colno, &s)
//fmt.Printf("d %d: %v\n", r-1, &d)
Swap(&d, &s)
if p1.pivots[k] < 0 {
k++ // skip other entry in 2x2 pivots
}
}
// ---------------------------------------------------------
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &A11, &A22, A, pTOPLEFT)
contPivot3x1to2x1(
&pT,
&pB, &p0, &p1, p, pTOP)
}
// do the last part with unblocked code
if ATL.Cols() > 0 {
unblkDecompBKUpper(&ATL, W, &pT)
}
return
}
func unblkBoundedLowerLDL(A, W *matrix.FloatMatrix, p *pPivots, ncol int) (error, int) {
var ATL, ATR, ABL, ABR matrix.FloatMatrix
var A00, a10, a11, A20, a21, A22, adiag, wcol matrix.FloatMatrix
var w00, w10, w11 matrix.FloatMatrix
var pT, pB, p0, p1, p2 pPivots
var err error = nil
partition2x2(
&ATL, &ATR,
&ABL, &ABR, A, 0, 0, pTOPLEFT)
partitionPivot2x1(
&pT,
&pB, p, 0, pTOP)
// copy current diagonal to last column of workspace
W.SubMatrix(&wcol, 0, W.Cols()-1, A.Rows(), 1)
A.Diag(&adiag)
adiag.CopyTo(&wcol)
//fmt.Printf("initial diagonal:\n%v\n", &wcol)
nc := 0
for ABR.Cols() > 0 && nc < ncol {
partition2x2(
&w00, nil,
&w10, &w11, W, nc, nc, pTOPLEFT)
dmax := findAndBuildPivot(&ABL, &ABR, &w10, &w11, nc)
//fmt.Printf("dmax=%d\n", dmax)
if dmax > 0 {
// pivot diagonal in symmetric matrix; will swap a11 [0,0] and [imax,imax]
applyPivotSym(&ABL, &ABR, dmax, LOWER)
swapRows(&w10, 0, dmax)
pB.pivots[0] = dmax + ATL.Rows() + 1
} else {
pB.pivots[0] = 0
}
//fmt.Printf("blk pivoted %d, A:\n%v\nW:\n%v\n", dmax, A, W)
repartition2x2to3x3(&ATL,
&A00, nil, nil,
&a10, &a11, nil,
&A20, &a21, &A22, A, 1, pBOTTOMRIGHT)
repartPivot2x1to3x1(&pT,
&p0, &p1, &p2 /**/, p, 1, pBOTTOM)
// --------------------------------------------------------
// Copy updated column from working space
w11.SubMatrix(&wcol, 1, 0, a21.Rows(), 1)
wcol.CopyTo(&a21)
a11.SetAt(0, 0, w11.GetAt(0, 0))
// l21 = a21/a11
InvScale(&a21, a11.Float())
// here: wcol == l21*d11 == a21
if ncol-nc > 1 {
// update diagonal in workspace if not last column of block
w11.SubMatrix(&adiag, 1, w11.Cols()-1, a21.Rows(), 1)
MVUpdateDiag(&adiag, &wcol, &wcol, -1.0/a11.Float())
}
//fmt.Printf("nc=%d, a11=%e\n", nc, a11.Float())
//fmt.Printf("l21\n%v\n", &a21)
//fmt.Printf("a21\n%v\n", &wcol)
//fmt.Printf("diag\n%v\n", &adiag)
//var Ablk, wblk matrix.FloatMatrix
//merge1x2(&Ablk, &ABL, &ABR)
//merge1x2(&wblk, &w10, &w11)
//fmt.Printf("unblk Ablk:\n%v\n", &Ablk)
//fmt.Printf("unblk wblk:\n%v\n", &wblk)
// ---------------------------------------------------------
nc++
continue3x3to2x2(
&ATL, &ATR,
&ABL, &ABR, &A00, &a11, &A22, A, pBOTTOMRIGHT)
contPivot3x1to2x1(
&pT,
&pB, &p0, &p1, p, pBOTTOM)
}
return err, nc
}
/*
* Apply diagonal pivot (row and column swapped) to symmetric matrix blocks.
* AR[0,0] is on diagonal and AL is block to the left of diagonal and AR the
* triangular diagonal block. Need to swap row and column.
*
* LOWER triangular; moving from top-left to bottom-right
*
* d
* x d |
* --------------------------
* x x | d
* S1 S1| S1 P1 x x x P2 -- current row/col 'srcix'
* x x | x S2 d x x x
* x x | x S2 x d x x
* x x | x S2 x x d x
* D1 D1| D1 P2 D2 D2 D2 P3 -- swap with row/col 'dstix'
* x x | x S3 x x x D3 d
* x x | x S3 x x x D3 x d
* (ABL) (ABR)
*
* UPPER triangular; moving from bottom-right to top-left
*
* (ATL) (ATR)
* d x x D3 x x x S3 x | x
* d x D3 x x x S3 x | x
* d D3 x x x S3 x | x
* P3 D2 D2 D2 P2 D1| D1 -- dstinx
* d x x S2 x | x
* d x S2 x | x
* d S2 x | x
* P1 S1| S1 -- srcinx
* d | x
* -----------------------------
* | d
* (ABR)
*/
func applyPivotSym2(AL, AR *matrix.FloatMatrix, srcix, dstix int, flags Flags) {
var s, d matrix.FloatMatrix
if flags&LOWER != 0 {
// AL is [ABL]; AR is [ABR]; P1 is AR[0,0], P2 is AR[index, 0]
// S1 -- D1
AL.SubMatrix(&s, srcix, 0, 1, AL.Cols())
AL.SubMatrix(&d, dstix, 0, 1, AL.Cols())
Swap(&s, &d)
if srcix > 0 {
AR.SubMatrix(&s, srcix, 0, 1, srcix)
AR.SubMatrix(&d, dstix, 0, 1, srcix)
Swap(&s, &d)
}
// S2 -- D2
AR.SubMatrix(&s, srcix+1, srcix, dstix-srcix-1, 1)
AR.SubMatrix(&d, dstix, srcix+1, 1, dstix-srcix-1)
Swap(&s, &d)
// S3 -- D3
AR.SubMatrix(&s, dstix+1, srcix, AR.Rows()-dstix-1, 1)
AR.SubMatrix(&d, dstix+1, dstix, AR.Rows()-dstix-1, 1)
Swap(&s, &d)
// swap P1 and P3
p1 := AR.GetAt(srcix, srcix)
p3 := AR.GetAt(dstix, dstix)
AR.SetAt(srcix, srcix, p3)
AR.SetAt(dstix, dstix, p1)
return
}
if flags&UPPER != 0 {
// AL is ATL, AR is ATR; P1 is AL[srcix, srcix];
// S1 -- D1;
AR.SubMatrix(&s, srcix, 0, 1, AR.Cols())
AR.SubMatrix(&d, dstix, 0, 1, AR.Cols())
Swap(&s, &d)
if srcix < AL.Cols()-1 {
// not the corner element
AL.SubMatrix(&s, srcix, srcix+1, 1, srcix)
AL.SubMatrix(&d, dstix, srcix+1, 1, srcix)
Swap(&s, &d)
}
// S2 -- D2
AL.SubMatrix(&s, dstix+1, srcix, srcix-dstix-1, 1)
AL.SubMatrix(&d, dstix, dstix+1, 1, srcix-dstix-1)
Swap(&s, &d)
// S3 -- D3
AL.SubMatrix(&s, 0, srcix, dstix, 1)
AL.SubMatrix(&d, 0, dstix, dstix, 1)
Swap(&s, &d)
//fmt.Printf("3, AR=%v\n", AR)
// swap P1 and P3
p1 := AR.GetAt(0, 0)
p3 := AL.GetAt(dstix, dstix)
AR.SetAt(srcix, srcix, p3)
AL.SetAt(dstix, dstix, p1)
return
}
}