/*! @file ilu_relax_snode.c * \brief Identify initial relaxed supernodes * *
* -- SuperLU routine (version 4.0) -- * Lawrence Berkeley National Laboratory * June 1, 2009 **/ #include "slu_ddefs.h" /*! \brief * *
* Purpose * ======= * ilu_relax_snode() - Identify the initial relaxed supernodes, assuming * that the matrix has been reordered according to the postorder of the * etree. **/ void ilu_relax_snode ( const int n, int *et, /* column elimination tree */ const int relax_columns, /* max no of columns allowed in a relaxed snode */ int *descendants, /* no of descendants of each node in the etree */ int *relax_end, /* last column in a supernode * if j-th column starts a relaxed * supernode, relax_end[j] represents * the last column of this supernode */ int *relax_fsupc /* first column in a supernode * relax_fsupc[j] represents the first * column of j-th supernode */ ) { register int j, f, parent; register int snode_start; /* beginning of a snode */ ifill (relax_end, n, EMPTY); ifill (relax_fsupc, n, EMPTY); for (j = 0; j < n; j++) descendants[j] = 0; /* Compute the number of descendants of each node in the etree */ for (j = 0; j < n; j++) { parent = et[j]; if ( parent != n ) /* not the dummy root */ descendants[parent] += descendants[j] + 1; } /* Identify the relaxed supernodes by postorder traversal of the etree. */ for (j = f = 0; j < n; ) { parent = et[j]; snode_start = j; while ( parent != n && descendants[parent] < relax_columns ) { j = parent; parent = et[j]; } /* Found a supernode with j being the last column. */ relax_end[snode_start] = j; /* Last column is recorded */ j++; relax_fsupc[f++] = snode_start; /* Search for a new leaf */ while ( descendants[j] != 0 && j < n ) j++; } }