/*! @file ilu_zpanel_dfs.c
* \brief Peforms a symbolic factorization on a panel of symbols and
* record the entries with maximum absolute value in each column
*
* <pre>
* -- SuperLU routine (version 4.0) --
* Lawrence Berkeley National Laboratory
* June 30, 2009
* </pre>
*/
#include "slu_zdefs.h"
/*! \brief
*
* <pre>
* Purpose
* =======
*
* Performs a symbolic factorization on a panel of columns [jcol, jcol+w).
*
* A supernode representative is the last column of a supernode.
* The nonzeros in U[*,j] are segments that end at supernodal
* representatives.
*
* The routine returns one list of the supernodal representatives
* in topological order of the dfs that generates them. This list is
* a superset of the topological order of each individual column within
* the panel.
* The location of the first nonzero in each supernodal segment
* (supernodal entry location) is also returned. Each column has a
* separate list for this purpose.
*
* Two marker arrays are used for dfs:
* marker[i] == jj, if i was visited during dfs of current column jj;
* marker1[i] >= jcol, if i was visited by earlier columns in this panel;
*
* marker: A-row --> A-row/col (0/1)
* repfnz: SuperA-col --> PA-row
* parent: SuperA-col --> SuperA-col
* xplore: SuperA-col --> index to L-structure
* </pre>
*/
void
ilu_zpanel_dfs(
const int m, /* in - number of rows in the matrix */
const int w, /* in */
const int jcol, /* in */
SuperMatrix *A, /* in - original matrix */
int *perm_r, /* in */
int *nseg, /* out */
doublecomplex *dense, /* out */
double *amax, /* out - max. abs. value of each column in panel */
int *panel_lsub, /* out */
int *segrep, /* out */
int *repfnz, /* out */
int *marker, /* out */
int *parent, /* working array */
int *xplore, /* working array */
GlobalLU_t *Glu /* modified */
)
{
NCPformat *Astore;
doublecomplex *a;
int *asub;
int *xa_begin, *xa_end;
int krep, chperm, chmark, chrep, oldrep, kchild, myfnz;
int k, krow, kmark, kperm;
int xdfs, maxdfs, kpar;
int jj; /* index through each column in the panel */
int *marker1; /* marker1[jj] >= jcol if vertex jj was visited
by a previous column within this panel. */
int *repfnz_col; /* start of each column in the panel */
doublecomplex *dense_col; /* start of each column in the panel */
int nextl_col; /* next available position in panel_lsub[*,jj] */
int *xsup, *supno;
int *lsub, *xlsub;
double *amax_col;
register double tmp;
/* Initialize pointers */
Astore = A->Store;
a = Astore->nzval;
asub = Astore->rowind;
xa_begin = Astore->colbeg;
xa_end = Astore->colend;
marker1 = marker + m;
repfnz_col = repfnz;
dense_col = dense;
amax_col = amax;
*nseg = 0;
xsup = Glu->xsup;
supno = Glu->supno;
lsub = Glu->lsub;
xlsub = Glu->xlsub;
/* For each column in the panel */
for (jj = jcol; jj < jcol + w; jj++) {
nextl_col = (jj - jcol) * m;
#ifdef CHK_DFS
printf("\npanel col %d: ", jj);
#endif
*amax_col = 0.0;
/* For each nonz in A[*,jj] do dfs */
for (k = xa_begin[jj]; k < xa_end[jj]; k++) {
krow = asub[k];
tmp = z_abs1(&a[k]);
if (tmp > *amax_col) *amax_col = tmp;
dense_col[krow] = a[k];
kmark = marker[krow];
if ( kmark == jj )
continue; /* krow visited before, go to the next nonzero */
/* For each unmarked nbr krow of jj
* krow is in L: place it in structure of L[*,jj]
*/
marker[krow] = jj;
kperm = perm_r[krow];
if ( kperm == EMPTY ) {
panel_lsub[nextl_col++] = krow; /* krow is indexed into A */
}
/*
* krow is in U: if its supernode-rep krep
* has been explored, update repfnz[*]
*/
else {
krep = xsup[supno[kperm]+1] - 1;
myfnz = repfnz_col[krep];
#ifdef CHK_DFS
printf("krep %d, myfnz %d, perm_r[%d] %d\n", krep, myfnz, krow, kperm);
#endif
if ( myfnz != EMPTY ) { /* Representative visited before */
if ( myfnz > kperm ) repfnz_col[krep] = kperm;
/* continue; */
}
else {
/* Otherwise, perform dfs starting at krep */
oldrep = EMPTY;
parent[krep] = oldrep;
repfnz_col[krep] = kperm;
xdfs = xlsub[xsup[supno[krep]]];
maxdfs = xlsub[krep + 1];
#ifdef CHK_DFS
printf(" xdfs %d, maxdfs %d: ", xdfs, maxdfs);
for (i = xdfs; i < maxdfs; i++) printf(" %d", lsub[i]);
printf("\n");
#endif
do {
/*
* For each unmarked kchild of krep
*/
while ( xdfs < maxdfs ) {
kchild = lsub[xdfs];
xdfs++;
chmark = marker[kchild];
if ( chmark != jj ) { /* Not reached yet */
marker[kchild] = jj;
chperm = perm_r[kchild];
/* Case kchild is in L: place it in L[*,j] */
if ( chperm == EMPTY ) {
panel_lsub[nextl_col++] = kchild;
}
/* Case kchild is in U:
* chrep = its supernode-rep. If its rep has
* been explored, update its repfnz[*]
*/
else {
chrep = xsup[supno[chperm]+1] - 1;
myfnz = repfnz_col[chrep];
#ifdef CHK_DFS
printf("chrep %d,myfnz %d,perm_r[%d] %d\n",chrep,myfnz,kchild,chperm);
#endif
if ( myfnz != EMPTY ) { /* Visited before */
if ( myfnz > chperm )
repfnz_col[chrep] = chperm;
}
else {
/* Cont. dfs at snode-rep of kchild */
xplore[krep] = xdfs;
oldrep = krep;
krep = chrep; /* Go deeper down G(L) */
parent[krep] = oldrep;
repfnz_col[krep] = chperm;
xdfs = xlsub[xsup[supno[krep]]];
maxdfs = xlsub[krep + 1];
#ifdef CHK_DFS
printf(" xdfs %d, maxdfs %d: ", xdfs, maxdfs);
for (i = xdfs; i < maxdfs; i++) printf(" %d", lsub[i]);
printf("\n");
#endif
} /* else */
} /* else */
} /* if... */
} /* while xdfs < maxdfs */
/* krow has no more unexplored nbrs:
* Place snode-rep krep in postorder DFS, if this
* segment is seen for the first time. (Note that
* "repfnz[krep]" may change later.)
* Backtrack dfs to its parent.
*/
if ( marker1[krep] < jcol ) {
segrep[*nseg] = krep;
++(*nseg);
marker1[krep] = jj;
}
kpar = parent[krep]; /* Pop stack, mimic recursion */
if ( kpar == EMPTY ) break; /* dfs done */
krep = kpar;
xdfs = xplore[krep];
maxdfs = xlsub[krep + 1];
#ifdef CHK_DFS
printf(" pop stack: krep %d,xdfs %d,maxdfs %d: ", krep,xdfs,maxdfs);
for (i = xdfs; i < maxdfs; i++) printf(" %d", lsub[i]);
printf("\n");
#endif
} while ( kpar != EMPTY ); /* do-while - until empty stack */
} /* else */
} /* else */
} /* for each nonz in A[*,jj] */
repfnz_col += m; /* Move to next column */
dense_col += m;
amax_col++;
} /* for jj ... */
}