solversamg.cpp

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/*
%M Esse módulo contem as funções para utilização da biblioteca SAMG
 *     06-07 André Luis Muller
 *     
 *
 */
#include <cstdio>
#include <iostream>
#include <fstream>

#include "samg.h"

/* the old C++ compiler on Alpha cannot handle using namespace std !*/
#ifndef SAMG_OLDALPHA
using namespace std;
#endif

#include "solversamg.h"
#include "fem.h"


int SamgSolver(int iversion, int nna, int nnu, int matrix, int nsys,
               int npnt,  int *ia, int *ja, double *a, double *f, double *u)
{

/* ===> Set primary parameters. Others can be set by access functions as shown below.*/

  int    ndiu      = 1;        /* dimension of (dummy) vector iu                            */
  int    ndip      = 1;        /* dimension of (dummy) vector ip                            */
                               /*                                                           */
  int    nsolve    = 2;        /* results in scalar approach (current system is scalar)     */
  int    ifirst    = 1;        /* first approximation = zero                                */
  double eps       = 1.0e-8;   /* required (relative) residual reduction                    */
  int    ncyc      = 110200;   /* V-cycle as pre-conditioner for GMRES; at most 200 iterations  */
                               /*                                                           */
  double a_cmplx   = 2.2;      /* estimated dimensioning                                    */
  double g_cmplx   = 1.7;      /* estimated dimensioning                                    */
  double w_avrge   = 2.4;      /* estimated dimensioning                                    */
  double p_cmplx   = 0.0;      /* estimated dimensioning (irrelevant for scalar case)       */
                               /*                                                           */
  double chktol    = -1.0;     /* input checking de-activated (we know it's ok!)            */
  int    idump     = 0;        /* minimum output during setup                               */
  int    iout      = -2;       /* no display residuals per iteration and work statistics    */
                               /*                                                           */
  int    n_default = 20;       /* select default settings for secondary parameters          */
                               /* CURRENTLY AVAILABLE: 10-13, 15-18, 20-23, 25-28           */
                               /* NOTE: the higher the respective SECOND digit, the         */
                               /* more aggressive the coarsening (--> lower memory at       */
                               /* the expense of slower convergence)                        */
  int    iswtch    = 5300+n_default; /* complete SAMG run ....*/
                               /* ... memory de-allocation upon return ....                 */                                   
                               /* ... memory extension feature activated ....               */
                               /* ... residuals measured in the L2-norm .....               */
                               /* ... secondary parameter default setting # n_default       */

/* ===> Secondary parameters which have to be set if n_default=0
      (at the same time a demonstration of how to access secondary or hidden parameters)*/
      int intin;
      double dblin;

      if (n_default == 0) {
         intin=25;    SAMG_SET_LEVELX(&intin);
         intin=100;   SAMG_SET_NPTMN(&intin);
         intin=4;     SAMG_SET_NCG(&intin);
         intin=2;     SAMG_SET_NWT(&intin);
         intin=1;     SAMG_SET_NTR(&intin);
         intin=131;   SAMG_SET_NRD(&intin);
         intin=131;   SAMG_SET_NRU(&intin);
         intin=0;     SAMG_SET_NRC(&intin);
         intin=0;     SAMG_SET_NP_OPT(&intin);

         dblin=21.25; SAMG_SET_ECG(&dblin);
         dblin=0.20;  SAMG_SET_EWT(&dblin);
         dblin=12.20; SAMG_SET_ETR(&dblin);
      }
      int * iu     = new int[1];
      int * ip     = new int[1];
      int * iscale = new int[1];

      int ierr,ncyc_done;
      double res_out,res_in;

      float told,tnew,tamg;
      SAMG_CTIME(&told);

      SAMG(&nnu,&nna,&nsys,
           &ia[0],&ja[0],&a[0],&f[0],&u[0],&iu[0],&ndiu,&ip[0],&ndip,&matrix,&iscale[0],
           &res_in,&res_out,&ncyc_done,&ierr,
           &nsolve,&ifirst,&eps,&ncyc,&iswtch,
           &a_cmplx,&g_cmplx,&p_cmplx,&w_avrge,
           &chktol,&idump,&iout);

      if (ierr > 0) {
          cout << endl << " SAMG terminated with error code " 
               << ierr << " **** " << endl;
      }
      else if (ierr < 0) {
          cout << endl << " SAMG terminated with warning code " 
               << ierr << " **** " << endl;
      }

      SAMG_CTIME(&tnew);
      tamg=tnew-told;
      cout << endl << " ***** total run time: " << tamg << " ***** " << endl; 
      
      delete[] iu;
      delete[] ip;
      delete[] iscale;

      return ierr;
}

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