/* 
 * -- Auxiliary routine in SuperLU (version 2.0) --
 * Lawrence Berkeley National Lab, Univ. of California Berkeley.
 * Xiaoye S. Li
 * September 11, 2003
 *
 */

#include "dsp_defs.h"


void dGetDiagU(SuperMatrix *L, double *diagU)
{
  /*
   * Purpose
   * =======
   *
   * GetDiagU extracts the main diagonal of matrix U of the LU factorization.
   *  
   * Arguments
   * =========
   *
   * L      (input) SuperMatrix*
   *        The factor L from the factorization Pr*A*Pc=L*U as computed by
   *        dgstrf(). Use compressed row subscripts storage for supernodes,
   *        i.e., L has types: Stype = SLU_SC, Dtype = SLU_D, Mtype = SLU_TRLU.
   *
   * diagU  (output) double*, dimension (n)
   *        The main diagonal of matrix U.
   *
   * Note
   * ====
   * The diagonal blocks of the L and U matrices are stored in the L
   * data structures.
   *
   */
    int_t i, k, nsupers;
    int_t fsupc, nsupr, nsupc, luptr;
    double *dblock, *Lval;
    SCformat *Lstore;

    Lstore = L->Store;
    Lval = Lstore->nzval;
    nsupers = Lstore->nsuper + 1;

    for (k = 0; k < nsupers; ++k) {
      fsupc = L_FST_SUPC(k);
      nsupc = L_FST_SUPC(k+1) - fsupc;
      nsupr = L_SUB_START(fsupc+1) - L_SUB_START(fsupc);
      luptr = L_NZ_START(fsupc);

      dblock = &diagU[fsupc];
      for (i = 0; i < nsupc; ++i) {
	dblock[i] = Lval[luptr];
	luptr += nsupr + 1;
      }
    }
}