text: #include "cs.h"
  /* C = A(p,p) where A and C are symmetric the upper part stored; pinv not p */
  cs *cs_symperm (const cs *A, const int *pinv, int values)
  {
      int i, j, p, q, i2, j2, n, *Ap, *Ai, *Cp, *Ci, *w ;
      double *Cx, *Ax ;
      cs *C ;
      if (!CS_CSC (A)) return (NULL) ;			/* check inputs */
      n = A->n ; Ap = A->p ; Ai = A->i ; Ax = A->x ;
      C = cs_spalloc (n, n, Ap [n], values && (Ax != NULL), 0) ; /* alloc result*/
      w = cs_calloc (n, sizeof (int)) ;			/* get workspace */
      if (!C || !w) return (cs_done (C, w, NULL, 0)) ;	/* out of memory */
      Cp = C->p ; Ci = C->i ; Cx = C->x ;
      for (j = 0 ; j < n ; j++)		/* count entries in each column of C */
      {
  	j2 = pinv ? pinv [j] : j ;	/* column j of A is column j2 of C */
  	for (p = Ap [j] ; p < Ap [j+1] ; p++)
  	{
  	    i = Ai [p] ;
  	    if (i > j) continue ;	/* skip lower triangular part of A */
  	    i2 = pinv ? pinv [i] : i ;	/* row i of A is row i2 of C */
  	    w [CS_MAX (i2, j2)]++ ;	/* column count of C */
  	}
      }
      cs_cumsum (Cp, w, n) ;		/* compute column pointers of C */
      for (j = 0 ; j < n ; j++)
      {
  	j2 = pinv ? pinv [j] : j ;	/* column j of A is column j2 of C */
  	for (p = Ap [j] ; p < Ap [j+1] ; p++)
  	{
  	    i = Ai [p] ;
  	    if (i > j) continue ;	/* skip lower triangular part of A*/
  	    i2 = pinv ? pinv [i] : i ;	/* row i of A is row i2 of C */
  	    Ci [q = w [CS_MAX (i2, j2)]++] = CS_MIN (i2, j2) ;
  	    if (Cx) Cx [q] = Ax [p] ;
  	}
      }
      return (cs_done (C, w, NULL, 1)) ;	/* success; free workspace, return C */
  }
  