unscale.c

a software code for computing selected eigenvalues of large sparse symmetric matrices

#include <string.h>
#include <ilupack.h>
#include <ilupackmacros.h>

// #define PRINT_INFO



void ILUPACKUNDOSCALING(size_t *Fparam, 
			size_t *FPREC,
			integer   *nlev,
			integer   *n,
			integer   *ia,
			integer   *ja,
			FLOAT     *a) {
   /*
     ILUPACK FORTRAN interface for initialization

     param       parameter pointer casted to INTEGER*8
     PRE         preconditioner pointer casted to INTEGER*8

     nlev        number of AMG levels

     n           size of the system

     ia          pointer         \
     ja          column indices  | of an NxN matrix in sparse row format
     a           numerical values/

   */

  ILUPACKPARAM *param;
  AMGLEVELMAT *PRE;
  FLOAT  *r, *c;
  REALS  val;
  integer      i,j,k;

  memcpy(&param, Fparam, sizeof(size_t));
  memcpy(&PRE,   FPREC,  sizeof(size_t));

    
  /* finally release memory of the preconditioner */
  r=PRE->rowscal;
  c=PRE->colscal;

  // adjust arrays
  ja--;
  a--;
  c--;
  for (i=0; i<*n; i++) {
      for (j=ia[i]; j<ia[i+1]; j++) {
	  k=ja[j];
#if defined _SINGLE_REAL_ || defined _DOUBLE_REAL_
	  a[j]/=r[i]*c[k];
#else
	  a[j].r/=r[i].r*c[k].r;
	  a[j].i/=r[i].r*c[k].r;
#endif	  
      }
  }

} // unscale