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/* ========================================================================== */
/* === UMF_utsolve ========================================================== */
/* ========================================================================== */
/* -------------------------------------------------------------------------- */
/* UMFPACK Copyright (c) Timothy A. Davis, CISE, */
/* Univ. of Florida. All Rights Reserved. See ../Doc/License for License. */
/* web: http://www.cise.ufl.edu/research/sparse/umfpack */
/* -------------------------------------------------------------------------- */
/* solves U'x = b or U.'x=b, where U is the upper triangular factor of a */
/* matrix. B is overwritten with the solution X. */
/* Returns the floating point operation count */
#include "umf_internal.h"
GLOBAL double
#ifdef CONJUGATE_SOLVE
UMF_uhsolve /* solve U'x=b (complex conjugate transpose) */
#else
UMF_utsolve /* solve U.'x=b (array transpose) */
#endif
(
NumericType *Numeric,
Entry X [ ], /* b on input, solution x on output */
Int Pattern [ ] /* a work array of size n */
)
{
/* ---------------------------------------------------------------------- */
/* local variables */
/* ---------------------------------------------------------------------- */
Entry xk ;
Entry *xp, *D, *Uval ;
Int k, deg, j, *ip, col, *Upos, *Uilen, kstart, kend, up,
*Uip, n, uhead, ulen, pos, npiv, n1, *Ui ;
/* ---------------------------------------------------------------------- */
/* get parameters */
/* ---------------------------------------------------------------------- */
if (Numeric->n_row != Numeric->n_col) return (0.) ;
n = Numeric->n_row ;
npiv = Numeric->npiv ;
Upos = Numeric->Upos ;
Uilen = Numeric->Uilen ;
Uip = Numeric->Uip ;
D = Numeric->D ;
kend = 0 ;
n1 = Numeric->n1 ;
#ifndef NDEBUG
DEBUG4 (("Utsolve start: npiv "ID" n "ID"
", npiv, n)) ;
for (j = 0 ; j < n ; j++)
{
DEBUG4 (("Utsolve start "ID": ", j)) ;
EDEBUG4 (X [j]) ;
DEBUG4 (("
")) ;
}
#endif
/* ---------------------------------------------------------------------- */
/* singletons */
/* ---------------------------------------------------------------------- */
for (k = 0 ; k < n1 ; k++)
{
DEBUG4 (("Singleton k "ID"
", k)) ;
#ifndef NO_DIVIDE_BY_ZERO
/* Go ahead and divide by zero if D [k] is zero. */
#ifdef CONJUGATE_SOLVE
/* xk = X [k] / conjugate (D [k]) ; */
DIV_CONJ (xk, X [k], D [k]) ;
#else
/* xk = X [k] / D [k] ; */
DIV (xk, X [k], D [k]) ;
#endif
#else
/* Do not divide by zero */
if (IS_NONZERO (D [k]))
{
#ifdef CONJUGATE_SOLVE
/* xk = X [k] / conjugate (D [k]) ; */
DIV_CONJ (xk, X [k], D [k]) ;
#else
/* xk = X [k] / D [k] ; */
DIV (xk, X [k], D [k]) ;
#endif
}
#endif
X [k] = xk ;
deg = Uilen [k] ;
if (deg > 0 && IS_NONZERO (xk))
{
up = Uip [k] ;
Ui = (Int *) (Numeric->Memory + up) ;
up += UNITS (Int, deg) ;
Uval = (Entry *) (Numeric->Memory + up) ;
for (j = 0 ; j < deg ; j++)
{
DEBUG4 ((" k "ID" col "ID" value", k, Ui [j])) ;
EDEBUG4 (Uval [j]) ;
DEBUG4 (("
")) ;
#ifdef CONJUGATE_SOLVE
/* X [Ui [j]] -= xk * conjugate (Uval [j]) ; */
MULT_SUB_CONJ (X [Ui [j]], xk, Uval [j]) ;
#else
/* X [Ui [j]] -= xk * Uval [j] ; */
MULT_SUB (X [Ui [j]], xk, Uval [j]) ;
#endif
}
}
}
/* ---------------------------------------------------------------------- */
/* nonsingletons */
/* ---------------------------------------------------------------------- */
for (kstart = n1 ; kstart < npiv ; kstart = kend + 1)
{
/* ------------------------------------------------------------------ */
/* find the end of this Uchain */
/* ------------------------------------------------------------------ */
DEBUG4 (("kstart "ID" kend "ID"
", kstart, kend)) ;
/* for (kend = kstart ; kend < npiv && Uip [kend+1] > 0 ; kend++) ; */
kend = kstart ;
while (kend < npiv && Uip [kend+1] > 0)
{
kend++ ;
}
/* ------------------------------------------------------------------ */
/* scan the whole Uchain to find the pattern of the first row of U */
/* ------------------------------------------------------------------ */
k = kend+1 ;
DEBUG4 (("
Kend "ID" K "ID"
", kend, k)) ;
/* ------------------------------------------------------------------ */
/* start with last row in Uchain of U in Pattern [0..deg-1] */
/* ------------------------------------------------------------------ */
if (k == npiv)
{
deg = Numeric->ulen ;
if (deg > 0)
{
/* :: make last pivot row of U (singular matrices only) :: */
for (j = 0 ; j < deg ; j++)
{
Pattern [j] = Numeric->Upattern [j] ;
}
}
}
else
{
ASSERT (k >= 0 && k < npiv) ;
up = -Uip [k] ;
ASSERT (up > 0) ;
deg = Uilen [k] ;
DEBUG4 (("end of chain for row of U "ID" deg "ID"
", k-1, deg)) ;
ip = (Int *) (Numeric->Memory + up) ;
for (j = 0 ; j < deg ; j++)
{
col = *ip++ ;
DEBUG4 ((" k "ID" col "ID"
", k-1, col)) ;
ASSERT (k <= col) ;
Pattern [j] = col ;
}
}
/* empty the stack at the bottom of Pattern */
uhead = n ;
for (k = kend ; k > kstart ; k--)
{
/* Pattern [0..deg-1] is the pattern of row k of U */
/* -------------------------------------------------------------- */
/* make row k-1 of U in Pattern [0..deg-1] */
/* -------------------------------------------------------------- */
ASSERT (k >= 0 && k < npiv) ;
ulen = Uilen [k] ;
/* delete, and push on the stack */
for (j = 0 ; j < ulen ; j++)
{
ASSERT (uhead >= deg) ;
Pattern [--uhead] = Pattern [--deg] ;
}
DEBUG4 (("middle of chain for row of U "ID" deg "ID"
", k, deg)) ;
ASSERT (deg >= 0) ;
pos = Upos [k] ;
if (pos != EMPTY)
{
/* add the pivot column */
DEBUG4 (("k "ID" add pivot entry at position "ID"
", k, pos)) ;
ASSERT (pos >= 0 && pos <= deg) ;
Pattern [deg++] = Pattern [pos] ;
Pattern [pos] = k ;
}
}
/* Pattern [0..deg-1] is now the pattern of the first row in Uchain */
/* ------------------------------------------------------------------ */
/* solve using this Uchain, in reverse order */
/* ------------------------------------------------------------------ */
DEBUG4 (("Unwinding Uchain
")) ;
for (k = kstart ; k <= kend ; k++)
{
/* -------------------------------------------------------------- */
/* construct row k */
/* -------------------------------------------------------------- */
ASSERT (k >= 0 && k < npiv) ;
pos = Upos [k] ;
if (pos != EMPTY)
{
/* remove the pivot column */
DEBUG4 (("k "ID" add pivot entry at position "ID"
", k, pos)) ;
ASSERT (k > kstart) ;
ASSERT (pos >= 0 && pos < deg) ;
ASSERT (Pattern [pos] == k) ;
Pattern [pos] = Pattern [--deg] ;
}
up = Uip [k] ;
ulen = Uilen [k] ;
if (k > kstart)
{
/* concatenate the deleted pattern; pop from the stack */
for (j = 0 ; j < ulen ; j++)
{
ASSERT (deg <= uhead && uhead < n) ;
Pattern [deg++] = Pattern [uhead++] ;
}
DEBUG4 (("middle of chain, row of U "ID" deg "ID"
", k, deg)) ;
ASSERT (deg >= 0) ;
}
/* -------------------------------------------------------------- */
/* use row k of U */
/* -------------------------------------------------------------- */
#ifndef NO_DIVIDE_BY_ZERO
/* Go ahead and divide by zero if D [k] is zero. */
#ifdef CONJUGATE_SOLVE
/* xk = X [k] / conjugate (D [k]) ; */
DIV_CONJ (xk, X [k], D [k]) ;
#else
/* xk = X [k] / D [k] ; */
DIV (xk, X [k], D [k]) ;
#endif
#else
/* Do not divide by zero */
if (IS_NONZERO (D [k]))
{
#ifdef CONJUGATE_SOLVE
/* xk = X [k] / conjugate (D [k]) ; */
DIV_CONJ (xk, X [k], D [k]) ;
#else
/* xk = X [k] / D [k] ; */
DIV (xk, X [k], D [k]) ;
#endif
}
#endif
X [k] = xk ;
if (IS_NONZERO (xk))
{
if (k == kstart)
{
up = -up ;
xp = (Entry *) (Numeric->Memory + up + UNITS (Int, ulen)) ;
}
else
{
xp = (Entry *) (Numeric->Memory + up) ;
}
for (j = 0 ; j < deg ; j++)
{
DEBUG4 ((" k "ID" col "ID" value", k, Pattern [j])) ;
EDEBUG4 (*xp) ;
DEBUG4 (("
")) ;
#ifdef CONJUGATE_SOLVE
/* X [Pattern [j]] -= xk * conjugate (*xp) ; */
MULT_SUB_CONJ (X [Pattern [j]], xk, *xp) ;
#else
/* X [Pattern [j]] -= xk * (*xp) ; */
MULT_SUB (X [Pattern [j]], xk, *xp) ;
#endif
xp++ ;
}
}
}
ASSERT (uhead == n) ;
}
#ifndef NO_DIVIDE_BY_ZERO
for (k = npiv ; k < n ; k++)
{
/* This is an *** intentional *** divide-by-zero, to get Inf or Nan,
* as appropriate. It is not a bug. */
ASSERT (IS_ZERO (D [k])) ;
/* For conjugate solve, D [k] == conjugate (D [k]), in this case */
/* xk = X [k] / D [k] ; */
DIV (xk, X [k], D [k]) ;
X [k] = xk ;
}
#endif
#ifndef NDEBUG
for (j = 0 ; j < n ; j++)
{
DEBUG4 (("Utsolve done "ID": ", j)) ;
EDEBUG4 (X [j]) ;
DEBUG4 (("
")) ;
}
DEBUG4 (("Utsolve done.
")) ;
#endif
return (DIV_FLOPS * ((double) n) + MULTSUB_FLOPS * ((double) Numeric->unz));
}
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