/*---------------------------------------------------------------
 * Programmer(s): Daniel R. Reynolds @ SMU
 *---------------------------------------------------------------
 * SUNDIALS Copyright Start
 * Copyright (c) 2002-2022, Lawrence Livermore National Security
 * and Southern Methodist University.
 * All rights reserved.
 *
 * See the top-level LICENSE and NOTICE files for details.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 * SUNDIALS Copyright End
 *---------------------------------------------------------------
 * Example problem:
 *
 * The following test simulates the Robertson problem,
 * corresponding to the kinetics of an autocatalytic reaction.
 * This is an ODE system with 3 components, Y = [u,v,w], satisfying
 * the equations,
 *    du/dt = -0.04*u + 1e4*v*w
 *    dv/dt = 0.04*u - 1e4*v*w - 3e7*v^2
 *    dw/dt = 3e7*v^2
 * for t in the interval [0.0, 1e11], with initial conditions
 * Y0 = [1,0,0].
 *
 * This program solves the problem with one of the solvers, ERK,
 * DIRK or ARK.  For DIRK and ARK, implicit subsystems are solved
 * using a Newton iteration with the dense SUNLinearSolver, and a
 * user-supplied Jacobian routine.
 *
 * 100 outputs are printed at equal intervals, and run statistics
 * are printed at the end.
 *---------------------------------------------------------------*/

/* Header files */
#include <stdio.h>
#include <math.h>
#include <arkode/arkode_arkstep.h>      /* prototypes for ARKStep fcts., consts */
#include <nvector/nvector_serial.h>     /* serial N_Vector types, fcts., macros */
#include <sunmatrix/sunmatrix_dense.h>  /* access to dense SUNMatrix            */
#include <sunlinsol/sunlinsol_dense.h>  /* access to dense SUNLinearSolver      */
#include <sundials/sundials_types.h>    /* defs. of 'realtype', 'sunindextype'  */

#if defined(SUNDIALS_EXTENDED_PRECISION)
#define GSYM "Lg"
#define ESYM "Le"
#define FSYM "Lf"
#else
#define GSYM "g"
#define ESYM "e"
#define FSYM "f"
#endif

/* User-supplied Functions Called by the Solver */
static int f(realtype t, N_Vector y, N_Vector ydot, void *user_data);
static int Jac(realtype t, N_Vector y, N_Vector fy, SUNMatrix J,
               void *user_data, N_Vector tmp1, N_Vector tmp2, N_Vector tmp3);

/* Private function to check function return values */
static int check_flag(void *flagvalue, const char *funcname, int opt);

/* Private function to check computed solution */
static int check_ans(N_Vector y, realtype t, realtype rtol, realtype atol);

/* Main Program */
int main()
{
  /* general problem parameters */
  realtype T0 = RCONST(0.0);     /* initial time */
  realtype Tf = RCONST(1.e11);   /* final time */
  realtype dTout = (Tf-T0)/100;  /* time between outputs */
  int Nt = (int) ceil(Tf/dTout); /* number of output times */
  sunindextype NEQ = 3;          /* number of dependent vars. */

  /* general problem variables */
  int flag;                      /* reusable error-checking flag */
  N_Vector y = NULL;             /* empty vector for storing solution */
  SUNMatrix A = NULL;            /* empty matrix for linear solver */
  SUNLinearSolver LS = NULL;     /* empty linear solver object */
  void *arkode_mem = NULL;       /* empty ARKode memory structure */
  FILE *UFID, *FID;
  realtype t, tout;
  int iout;

  /* set up the initial conditions, tolerances, initial time step size */
  realtype u0 = RCONST(1.0);
  realtype v0 = RCONST(0.0);
  realtype w0 = RCONST(0.0);
  realtype reltol = RCONST(1.0e-4);
  realtype abstol = RCONST(1.0e-11);
  realtype h0 = RCONST(1.0e-4) * reltol;

  /* Create the SUNDIALS context object for this simulation */
  SUNContext ctx;
  flag = SUNContext_Create(NULL, &ctx);
  if (check_flag(&flag, "SUNContext_Create", 1)) return 1;

  /* Initial problem output */
  printf("\nRobertson ODE test problem:\n");
  printf("    initial conditions:  u0 = %"GSYM",  v0 = %"GSYM",  w0 = %"GSYM"\n",u0,v0,w0);

  /* Initialize data structures */
  y = N_VNew_Serial(NEQ, ctx);         /* Create serial vector for solution */
  if (check_flag((void *) y, "N_VNew_Serial", 0)) return 1;
  NV_Ith_S(y,0) = u0;             /* Set initial conditions into y */
  NV_Ith_S(y,1) = v0;
  NV_Ith_S(y,2) = w0;

  /* Call ARKStepCreate to initialize the ARK timestepper module and
     specify the right-hand side function in y'=f(t,y), the inital time
     T0, and the initial dependent variable vector y.  Note: since this
     problem is fully implicit, we set f_E to NULL and f_I to f. */
  arkode_mem = ARKStepCreate(NULL, f, T0, y, ctx);
  if (check_flag((void *)arkode_mem, "ARKStepCreate", 0)) return 1;

  /* Set routines */
  flag = ARKStepSetInitStep(arkode_mem, h0);                  /* Set custom initial step */
  if (check_flag(&flag, "ARKStepSetInitStep", 1)) return 1;
  flag = ARKStepSetMaxErrTestFails(arkode_mem, 20);           /* Increase max error test fails */
  if (check_flag(&flag, "ARKStepSetMaxErrTestFails", 1)) return 1;
  flag = ARKStepSetMaxNonlinIters(arkode_mem, 8);             /* Increase max nonlin iters  */
  if (check_flag(&flag, "ARKStepSetMaxNonlinIters", 1)) return 1;
  flag = ARKStepSetNonlinConvCoef(arkode_mem, RCONST(1.e-7)); /* Set nonlinear convergence coeff. */
  if (check_flag(&flag, "ARKStepSetNonlinConvCoef", 1)) return 1;
  flag = ARKStepSetMaxNumSteps(arkode_mem, 100000);           /* Increase max num steps */
  if (check_flag(&flag, "ARKStepSetMaxNumSteps", 1)) return 1;
  flag = ARKStepSetPredictorMethod(arkode_mem, 1);            /* Specify maximum-order predictor */
  if (check_flag(&flag, "ARKStepSetPredictorMethod", 1)) return 1;
  flag = ARKStepSStolerances(arkode_mem, reltol, abstol);     /* Specify tolerances */
  if (check_flag(&flag, "ARKStepSStolerances", 1)) return 1;

  /* Initialize dense matrix data structure and solver */
  A = SUNDenseMatrix(NEQ, NEQ, ctx);
  if (check_flag((void *)A, "SUNDenseMatrix", 0)) return 1;
  LS = SUNLinSol_Dense(y, A, ctx);
  if (check_flag((void *)LS, "SUNLinSol_Dense", 0)) return 1;

  /* Linear solver interface */
  flag = ARKStepSetLinearSolver(arkode_mem, LS, A);        /* Attach matrix and linear solver */
  if (check_flag(&flag, "ARKStepSetLinearSolver", 1)) return 1;
  flag = ARKStepSetJacFn(arkode_mem, Jac);                 /* Set the Jacobian routine */
  if (check_flag(&flag, "ARKStepSetJacFn", 1)) return 1;

  /* Open output stream for results, output comment line */
  UFID = fopen("solution.txt","w");
  fprintf(UFID,"# t u v w\n");

  /* output initial condition to disk */
  fprintf(UFID," %.16"ESYM" %.16"ESYM" %.16"ESYM" %.16"ESYM"\n",
          T0, NV_Ith_S(y,0), NV_Ith_S(y,1), NV_Ith_S(y,2));

  /* Main time-stepping loop: calls ARKStepEvolve to perform the integration, then
     prints results.  Stops when the final time has been reached */
  t = T0;
  tout = T0+dTout;
  printf("        t           u           v           w\n");
  printf("   --------------------------------------------------\n");
  printf("  %10.3"ESYM"  %12.5"ESYM"  %12.5"ESYM"  %12.5"ESYM"\n",
      t, NV_Ith_S(y,0), NV_Ith_S(y,1), NV_Ith_S(y,2));
  for (iout=0; iout<Nt; iout++) {

    flag = ARKStepEvolve(arkode_mem, tout, y, &t, ARK_NORMAL);       /* call integrator */
    if (check_flag(&flag, "ARKStepEvolve", 1)) break;
    printf("  %10.3"ESYM"  %12.5"ESYM"  %12.5"ESYM"  %12.5"ESYM"\n",              /* access/print solution */
           t, NV_Ith_S(y,0), NV_Ith_S(y,1), NV_Ith_S(y,2));
    fprintf(UFID," %.16"ESYM" %.16"ESYM" %.16"ESYM" %.16"ESYM"\n",
            t, NV_Ith_S(y,0), NV_Ith_S(y,1), NV_Ith_S(y,2));
    if (flag >= 0) {                                          /* successful solve: update time */
      tout += dTout;
      tout = (tout > Tf) ? Tf : tout;
    } else {                                                  /* unsuccessful solve: break */
      fprintf(stderr,"Solver failure, stopping integration\n");
      break;
    }
  }
  printf("   --------------------------------------------------\n");
  fclose(UFID);

  /* Print final statistics to the screen */
  printf("\nFinal Statistics:\n");
  flag = ARKStepPrintAllStats(arkode_mem, stdout, SUN_OUTPUTFORMAT_TABLE);

  /* Print final statistics to a file in CSV format */
  FID = fopen("ark_robertson_stats.csv", "w");
  flag = ARKStepPrintAllStats(arkode_mem, FID, SUN_OUTPUTFORMAT_CSV);
  fclose(FID);

  /* check the solution error */
  flag = check_ans(y, t, reltol, abstol);

  /* Clean up and return with successful completion */
  N_VDestroy(y);               /* Free y vector */
  ARKStepFree(&arkode_mem);    /* Free integrator memory */
  SUNLinSolFree(LS);           /* Free linear solver */
  SUNMatDestroy(A);            /* Free A matrix */
  SUNContext_Free(&ctx);       /* Free context */

  return flag;
}

/*-------------------------------
 * Functions called by the solver
 *-------------------------------*/

/* f routine to compute the ODE RHS function f(t,y). */
static int f(realtype t, N_Vector y, N_Vector ydot, void *user_data)
{
  realtype u = NV_Ith_S(y,0);   /* access current solution */
  realtype v = NV_Ith_S(y,1);
  realtype w = NV_Ith_S(y,2);

  /* Fill in ODE RHS function */
  NV_Ith_S(ydot,0) = -0.04*u + 1.e4*v*w;
  NV_Ith_S(ydot,1) = 0.04*u - 1.e4*v*w - 3.e7*v*v;
  NV_Ith_S(ydot,2) = 3.e7*v*v;

  return 0;                     /* Return with success */
}

/* Jacobian routine to compute J(t,y) = df/dy. */
static int Jac(realtype t, N_Vector y, N_Vector fy, SUNMatrix J,
               void *user_data, N_Vector tmp1, N_Vector tmp2, N_Vector tmp3)
{
  realtype v = NV_Ith_S(y,1);   /* access current solution */
  realtype w = NV_Ith_S(y,2);
  SUNMatZero(J);                /* initialize Jacobian to zero */

  /* Fill in the Jacobian of the ODE RHS function */
  SM_ELEMENT_D(J,0,0) = -0.04;
  SM_ELEMENT_D(J,0,1) = 1.e4*w;
  SM_ELEMENT_D(J,0,2) = 1.e4*v;

  SM_ELEMENT_D(J,1,0) = 0.04;
  SM_ELEMENT_D(J,1,1) = -1.e4*w - 6.e7*v;
  SM_ELEMENT_D(J,1,2) = -1.e4*v;

  SM_ELEMENT_D(J,2,1) = 6.e7*v;

  return 0;                     /* Return with success */
}

/*-------------------------------
 * Private helper functions
 *-------------------------------*/

/* Check function return value...
    opt == 0 means SUNDIALS function allocates memory so check if
             returned NULL pointer
    opt == 1 means SUNDIALS function returns a flag so check if
             flag >= 0
    opt == 2 means function allocates memory so check if returned
             NULL pointer
*/
static int check_flag(void *flagvalue, const char *funcname, int opt)
{
  int *errflag;

  /* Check if SUNDIALS function returned NULL pointer - no memory allocated */
  if (opt == 0 && flagvalue == NULL) {
    fprintf(stderr, "\nSUNDIALS_ERROR: %s() failed - returned NULL pointer\n\n",
            funcname);
    return 1; }

  /* Check if flag < 0 */
  else if (opt == 1) {
    errflag = (int *) flagvalue;
    if (*errflag < 0) {
      fprintf(stderr, "\nSUNDIALS_ERROR: %s() failed with flag = %d\n\n",
              funcname, *errflag);
      return 1; }}

  /* Check if function returned NULL pointer - no memory allocated */
  else if (opt == 2 && flagvalue == NULL) {
    fprintf(stderr, "\nMEMORY_ERROR: %s() failed - returned NULL pointer\n\n",
            funcname);
    return 1; }

  return 0;
}

/* compare the solution at the final time 1e11s to a reference solution computed
   using a relative tolerance of 1e-8 and absoltue tolerance of 1e-14 */
static int check_ans(N_Vector y, realtype t, realtype rtol, realtype atol)
{
  int      passfail=0;        /* answer pass (0) or fail (1) flag */
  N_Vector ref;               /* reference solution vector        */
  N_Vector ewt;               /* error weight vector              */
  realtype err;               /* wrms error                       */
  realtype ZERO=RCONST(0.0);
  realtype ONE=RCONST(1.0);

  /* create reference solution and error weight vectors */
  ref = N_VClone(y);
  ewt = N_VClone(y);

  /* set the reference solution data */
  NV_Ith_S(ref,0) = RCONST(2.0833403356917897e-08);
  NV_Ith_S(ref,1) = RCONST(8.1470714598028223e-14);
  NV_Ith_S(ref,2) = RCONST(9.9999997916651040e-01);

  /* compute the error weight vector */
  N_VAbs(ref, ewt);
  N_VScale(rtol, ewt, ewt);
  N_VAddConst(ewt, atol, ewt);
  if (N_VMin(ewt) <= ZERO) {
    fprintf(stderr, "\nSUNDIALS_ERROR: check_ans failed - ewt <= 0\n\n");
    return(-1);
  }
  N_VInv(ewt, ewt);

  /* compute the solution error */
  N_VLinearSum(ONE, y, -ONE, ref, ref);
  err = N_VWrmsNorm(ref, ewt);

  /* is the solution within the tolerances? */
  passfail = (err < ONE) ? 0 : 1;

  if (passfail) {
    fprintf(stdout, "\nSUNDIALS_WARNING: check_ans error=%"GSYM"\n\n", err);
  }

  /* Free vectors */
  N_VDestroy(ref);
  N_VDestroy(ewt);

  return(passfail);
}

/*---- end of file ----*/