/* -----------------------------------------------------------------
 * Programmer(s): Scott D. Cohen, Alan C. Hindmarsh and
 *                Radu Serban @LLNL
 * -----------------------------------------------------------------
 * SUNDIALS Copyright Start
 * Copyright (c) 2002-2024, 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:
 *
 * An ODE system is generated from the following 2-species diurnal
 * kinetics advection-diffusion PDE system in 2 space dimensions:
 *
 * dc(i)/dt = Kh*(d/dx)^2 c(i) + V*dc(i)/dx + (d/dy)(Kv(y)*dc(i)/dy)
 *                 + Ri(c1,c2,t)      for i = 1,2,   where
 *   R1(c1,c2,t) = -q1*c1*c3 - q2*c1*c2 + 2*q3(t)*c3 + q4(t)*c2 ,
 *   R2(c1,c2,t) =  q1*c1*c3 - q2*c1*c2 - q4(t)*c2 ,
 *   Kv(y) = Kv0*exp(y/5) ,
 * Kh, V, Kv0, q1, q2, and c3 are constants, and q3(t) and q4(t)
 * vary diurnally. The problem is posed on the square
 *   0 <= x <= 20,    30 <= y <= 50   (all in km),
 * with homogeneous Neumann boundary conditions, and for time t in
 *   0 <= t <= 86400 sec (1 day).
 * The PDE system is treated by central differences on a uniform
 * 10 x 10 mesh, with simple polynomial initial profiles.
 * The problem is solved with CVODES, with the BDF/GMRES
 * method (i.e. using the SUNLinSol_SPGMR linear solver) and a banded
 * preconditioner, generated by difference quotients, using the
 * module CVBANDPRE. The problem is solved with left and right
 * preconditioning.
 * -----------------------------------------------------------------
 */

#include <cvodes/cvodes.h>         /* main integrator header file          */
#include <cvodes/cvodes_bandpre.h> /* access to CVBANDPRE module           */
#include <math.h>
#include <nvector/nvector_serial.h> /* access to serial N_Vector            */
#include <stdio.h>
#include <stdlib.h>
#include <sundials/sundials_types.h> /* defs. of sunrealtype, sunindextype      */
#include <sunlinsol/sunlinsol_spgmr.h> /* access to SPGMR SUNLinearSolver      */

/* helpful macros */

#ifndef SQR
#define SQR(A) ((A) * (A))
#endif

/* Problem Constants */

#define ZERO SUN_RCONST(0.0)
#define ONE  SUN_RCONST(1.0)
#define TWO  SUN_RCONST(2.0)

#define NUM_SPECIES 2                    /* number of species         */
#define KH          SUN_RCONST(4.0e-6)   /* horizontal diffusivity Kh */
#define VEL         SUN_RCONST(0.001)    /* advection velocity V      */
#define KV0         SUN_RCONST(1.0e-8)   /* coefficient in Kv(y)      */
#define Q1          SUN_RCONST(1.63e-16) /* coefficients q1, q2, c3   */
#define Q2          SUN_RCONST(4.66e-16)
#define C3          SUN_RCONST(3.7e16)
#define A3          SUN_RCONST(22.62) /* coefficient in expression for q3(t) */
#define A4          SUN_RCONST(7.601) /* coefficient in expression for q4(t) */
#define C1_SCALE    SUN_RCONST(1.0e6) /* coefficients in initial profiles    */
#define C2_SCALE    SUN_RCONST(1.0e12)

#define T0      ZERO               /* initial time */
#define NOUT    12                 /* number of output times */
#define TWOHR   SUN_RCONST(7200.0) /* number of seconds in two hours  */
#define HALFDAY SUN_RCONST(4.32e4) /* number of seconds in a half day */
#define PI      SUN_RCONST(3.1415926535898) /* pi */

#define XMIN ZERO /* grid boundaries in x  */
#define XMAX SUN_RCONST(20.0)
#define YMIN SUN_RCONST(30.0) /* grid boundaries in y  */
#define YMAX SUN_RCONST(50.0)
#define XMID SUN_RCONST(10.0) /* grid midpoints in x,y */
#define YMID SUN_RCONST(40.0)

#define MX   10        /* MX = number of x mesh points */
#define MY   10        /* MY = number of y mesh points */
#define NSMX 20        /* NSMX = NUM_SPECIES*MX */
#define MM   (MX * MY) /* MM = MX*MY */

/* CVodeInit Constants */

#define RTOL  SUN_RCONST(1.0e-5) /* scalar relative tolerance */
#define FLOOR SUN_RCONST(100.0)  /* value of C1 or C2 at which tolerances */
                                 /* change from relative to absolute      */
#define ATOL (RTOL * FLOOR)      /* scalar absolute tolerance */
#define NEQ  (NUM_SPECIES * MM)  /* NEQ = number of equations */

/* User-defined vector and matrix accessor macros: IJKth, IJth */

/* IJKth is defined in order to isolate the translation from the
   mathematical 3-dimensional structure of the dependent variable vector
   to the underlying 1-dimensional storage. IJth is defined in order to
   write code which indexes into small dense matrices with a (row,column)
   pair, where 1 <= row, column <= NUM_SPECIES.

   IJKth(vdata,i,j,k) references the element in the vdata array for
   species i at mesh point (j,k), where 1 <= i <= NUM_SPECIES,
   0 <= j <= MX-1, 0 <= k <= MY-1. The vdata array is obtained via
   the call vdata = N_VGetArrayPointer(v), where v is an N_Vector.
   For each mesh point (j,k), the elements for species i and i+1 are
   contiguous within vdata.

   IJth(a,i,j) references the (i,j)th entry of the small matrix sunrealtype **a,
   where 1 <= i,j <= NUM_SPECIES. The small matrix routines in dense.h
   work with matrices stored by column in a 2-dimensional array. In C,
   arrays are indexed starting at 0, not 1. */

#define IJKth(vdata, i, j, k) (vdata[i - 1 + (j) * NUM_SPECIES + (k) * NSMX])
#define IJth(a, i, j)         (a[j - 1][i - 1])

/* Type : UserData
   contains problem constants */

typedef struct
{
  sunrealtype q4, om, dx, dy, hdco, haco, vdco;
}* UserData;

/* Private Helper Functions */

static void InitUserData(UserData data);
static void SetInitialProfiles(N_Vector u, sunrealtype dx, sunrealtype dy);
static void PrintIntro(sunindextype mu, sunindextype ml);
static void PrintOutput(void* cvode_mem, N_Vector u, sunrealtype t);
static void PrintFinalStats(void* cvode_mem);

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

/* Function Called by the Solver */

static int f(sunrealtype t, N_Vector u, N_Vector udot, void* user_data);

/*
 *-------------------------------
 * Main Program
 *-------------------------------
 */

int main(void)
{
  SUNContext sunctx;
  sunrealtype abstol, reltol, t, tout;
  N_Vector u;
  UserData data;
  SUNLinearSolver LS;
  void* cvode_mem;
  int retval, iout, jpre;
  sunindextype ml, mu;

  u         = NULL;
  data      = NULL;
  LS        = NULL;
  cvode_mem = NULL;

  /* Create the SUNDIALS simulation context that all SUNDIALS objects require */
  retval = SUNContext_Create(SUN_COMM_NULL, &sunctx);
  if (check_retval(&retval, "SUNContext_Create", 1)) { return (1); }

  /* Allocate and initialize u, and set problem data and tolerances */
  u = N_VNew_Serial(NEQ, sunctx);
  if (check_retval((void*)u, "N_VNew_Serial", 0)) { return (1); }
  data = (UserData)malloc(sizeof *data);
  if (check_retval((void*)data, "malloc", 2)) { return (1); }
  InitUserData(data);
  SetInitialProfiles(u, data->dx, data->dy);
  abstol = ATOL;
  reltol = RTOL;

  /* Call CVodeCreate to create the solver memory and specify the
   * Backward Differentiation Formula */
  cvode_mem = CVodeCreate(CV_BDF, sunctx);
  if (check_retval((void*)cvode_mem, "CVodeCreate", 0)) { return (1); }

  /* Set the pointer to user-defined data */
  retval = CVodeSetUserData(cvode_mem, data);
  if (check_retval(&retval, "CVodeSetUserData", 1)) { return (1); }

  /* Call CVodeInit to initialize the integrator memory and specify the
   * user's right hand side function in u'=f(t,u), the inital time T0, and
   * the initial dependent variable vector u. */
  retval = CVodeInit(cvode_mem, f, T0, u);
  if (check_retval(&retval, "CVodeInit", 1)) { return (1); }

  /* Call CVodeSStolerances to specify the scalar relative tolerance
   * and scalar absolute tolerances */
  retval = CVodeSStolerances(cvode_mem, reltol, abstol);
  if (check_retval(&retval, "CVodeSStolerances", 1)) { return (1); }

  /* Call SUNLinSol_SPGMR to specify the linear solver SUNLinSol_SPGMR
   * with left preconditioning and the default Krylov dimension */
  LS = SUNLinSol_SPGMR(u, SUN_PREC_LEFT, 0, sunctx);
  if (check_retval((void*)LS, "SUNLinSol_SPGMR", 0)) { return (1); }

  /* Call CVodeSetLinearSolver to attach the linear sovler to CVode */
  retval = CVodeSetLinearSolver(cvode_mem, LS, NULL);
  if (check_retval(&retval, "CVodeSetLinearSolver", 1)) { return 1; }

  /* Call CVBandPreInit to initialize band preconditioner */
  ml = mu = 2;
  retval  = CVBandPrecInit(cvode_mem, NEQ, mu, ml);
  if (check_retval(&retval, "CVBandPrecInit", 0)) { return (1); }

  PrintIntro(mu, ml);

  /* Loop over jpre (= SUN_PREC_LEFT, SUN_PREC_RIGHT), and solve the problem */

  for (jpre = SUN_PREC_LEFT; jpre <= SUN_PREC_RIGHT; jpre++)
  {
    /* On second run, re-initialize u, the solver, and SPGMR */

    if (jpre == SUN_PREC_RIGHT)
    {
      SetInitialProfiles(u, data->dx, data->dy);

      retval = CVodeReInit(cvode_mem, T0, u);
      if (check_retval(&retval, "CVodeReInit", 1)) { return (1); }

      retval = SUNLinSol_SPGMRSetPrecType(LS, SUN_PREC_RIGHT);
      if (check_retval(&retval, "SUNLinSol_SPGMRSetPrecType", 1))
      {
        return (1);
      }

      retval = CVBandPrecInit(cvode_mem, NEQ, mu, ml);
      if (check_retval(&retval, "CVBandPrecInit", 0)) { return (1); }

      printf("\n\n-------------------------------------------------------");
      printf("------------\n");
    }

    printf("\n\nPreconditioner type is:  jpre = %s\n\n",
           (jpre == SUN_PREC_LEFT) ? "SUN_PREC_LEFT" : "SUN_PREC_RIGHT");

    /* In loop over output points, call CVode, print results, test for error */

    for (iout = 1, tout = TWOHR; iout <= NOUT; iout++, tout += TWOHR)
    {
      retval = CVode(cvode_mem, tout, u, &t, CV_NORMAL);
      check_retval(&retval, "CVode", 1);
      PrintOutput(cvode_mem, u, t);
      if (retval != CV_SUCCESS) { break; }
    }

    /* Print final statistics */

    PrintFinalStats(cvode_mem);

  } /* End of jpre loop */

  /* Free memory */
  N_VDestroy(u);
  free(data);
  CVodeFree(&cvode_mem);
  SUNLinSolFree(LS);
  SUNContext_Free(&sunctx);

  return (0);
}

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

/* Load problem constants in data */

static void InitUserData(UserData data)
{
  data->om   = PI / HALFDAY;
  data->dx   = (XMAX - XMIN) / (MX - 1);
  data->dy   = (YMAX - YMIN) / (MY - 1);
  data->hdco = KH / SQR(data->dx);
  data->haco = VEL / (TWO * data->dx);
  data->vdco = (ONE / SQR(data->dy)) * KV0;
}

/* Set initial conditions in u */

static void SetInitialProfiles(N_Vector u, sunrealtype dx, sunrealtype dy)
{
  int jx, jy;
  sunrealtype x, y, cx, cy;
  sunrealtype* udata;

  /* Set pointer to data array in vector u. */

  udata = N_VGetArrayPointer(u);

  /* Load initial profiles of c1 and c2 into u vector */

  for (jy = 0; jy < MY; jy++)
  {
    y  = YMIN + jy * dy;
    cy = SQR(SUN_RCONST(0.1) * (y - YMID));
    cy = ONE - cy + SUN_RCONST(0.5) * SQR(cy);
    for (jx = 0; jx < MX; jx++)
    {
      x                       = XMIN + jx * dx;
      cx                      = SQR(SUN_RCONST(0.1) * (x - XMID));
      cx                      = ONE - cx + SUN_RCONST(0.5) * SQR(cx);
      IJKth(udata, 1, jx, jy) = C1_SCALE * cx * cy;
      IJKth(udata, 2, jx, jy) = C2_SCALE * cx * cy;
    }
  }
}

static void PrintIntro(sunindextype mu, sunindextype ml)
{
  printf("2-species diurnal advection-diffusion problem, %d by %d mesh\n", MX,
         MY);
  printf("SPGMR solver; band preconditioner; mu = %ld, ml = %ld\n\n",
         (long int)mu, (long int)ml);

  return;
}

/* Print current t, step count, order, stepsize, and sampled c1,c2 values */

static void PrintOutput(void* cvode_mem, N_Vector u, sunrealtype t)
{
  long int nst;
  int qu, retval;
  sunrealtype hu, *udata;
  int mxh = MX / 2 - 1, myh = MY / 2 - 1, mx1 = MX - 1, my1 = MY - 1;

  udata = N_VGetArrayPointer(u);

  retval = CVodeGetNumSteps(cvode_mem, &nst);
  check_retval(&retval, "CVodeGetNumSteps", 1);
  retval = CVodeGetLastOrder(cvode_mem, &qu);
  check_retval(&retval, "CVodeGetLastOrder", 1);
  retval = CVodeGetLastStep(cvode_mem, &hu);
  check_retval(&retval, "CVodeGetLastStep", 1);

#if defined(SUNDIALS_EXTENDED_PRECISION)
  printf("t = %.2Le   no. steps = %ld   order = %d   stepsize = %.2Le\n", t,
         nst, qu, hu);
  printf("c1 (bot.left/middle/top rt.) = %12.3Le  %12.3Le  %12.3Le\n",
         IJKth(udata, 1, 0, 0), IJKth(udata, 1, mxh, myh),
         IJKth(udata, 1, mx1, my1));
  printf("c2 (bot.left/middle/top rt.) = %12.3Le  %12.3Le  %12.3Le\n\n",
         IJKth(udata, 2, 0, 0), IJKth(udata, 2, mxh, myh),
         IJKth(udata, 2, mx1, my1));
#elif defined(SUNDIALS_DOUBLE_PRECISION)
  printf("t = %.2e   no. steps = %ld   order = %d   stepsize = %.2e\n", t, nst,
         qu, hu);
  printf("c1 (bot.left/middle/top rt.) = %12.3e  %12.3e  %12.3e\n",
         IJKth(udata, 1, 0, 0), IJKth(udata, 1, mxh, myh),
         IJKth(udata, 1, mx1, my1));
  printf("c2 (bot.left/middle/top rt.) = %12.3e  %12.3e  %12.3e\n\n",
         IJKth(udata, 2, 0, 0), IJKth(udata, 2, mxh, myh),
         IJKth(udata, 2, mx1, my1));
#else
  printf("t = %.2e   no. steps = %ld   order = %d   stepsize = %.2e\n", t, nst,
         qu, hu);
  printf("c1 (bot.left/middle/top rt.) = %12.3e  %12.3e  %12.3e\n",
         IJKth(udata, 1, 0, 0), IJKth(udata, 1, mxh, myh),
         IJKth(udata, 1, mx1, my1));
  printf("c2 (bot.left/middle/top rt.) = %12.3e  %12.3e  %12.3e\n\n",
         IJKth(udata, 2, 0, 0), IJKth(udata, 2, mxh, myh),
         IJKth(udata, 2, mx1, my1));
#endif
}

/* Get and print final statistics */

static void PrintFinalStats(void* cvode_mem)
{
  long int lenrw, leniw;
  long int lenrwLS, leniwLS;
  long int lenrwBP, leniwBP;
  long int nst, nfe, nsetups, nni, ncfn, netf;
  long int nli, npe, nps, ncfl, nfeLS;
  long int nfeBP;
  int retval;

  retval = CVodeGetWorkSpace(cvode_mem, &lenrw, &leniw);
  check_retval(&retval, "CVodeGetWorkSpace", 1);
  retval = CVodeGetNumSteps(cvode_mem, &nst);
  check_retval(&retval, "CVodeGetNumSteps", 1);
  retval = CVodeGetNumRhsEvals(cvode_mem, &nfe);
  check_retval(&retval, "CVodeGetNumRhsEvals", 1);
  retval = CVodeGetNumLinSolvSetups(cvode_mem, &nsetups);
  check_retval(&retval, "CVodeGetNumLinSolvSetups", 1);
  retval = CVodeGetNumErrTestFails(cvode_mem, &netf);
  check_retval(&retval, "CVodeGetNumErrTestFails", 1);
  retval = CVodeGetNumNonlinSolvIters(cvode_mem, &nni);
  check_retval(&retval, "CVodeGetNumNonlinSolvIters", 1);
  retval = CVodeGetNumNonlinSolvConvFails(cvode_mem, &ncfn);
  check_retval(&retval, "CVodeGetNumNonlinSolvConvFails", 1);

  retval = CVodeGetLinWorkSpace(cvode_mem, &lenrwLS, &leniwLS);
  check_retval(&retval, "CVodeGetLinWorkSpace", 1);
  retval = CVodeGetNumLinIters(cvode_mem, &nli);
  check_retval(&retval, "CVodeGetNumLinIters", 1);
  retval = CVodeGetNumPrecEvals(cvode_mem, &npe);
  check_retval(&retval, "CVodeGetNumPrecEvals", 1);
  retval = CVodeGetNumPrecSolves(cvode_mem, &nps);
  check_retval(&retval, "CVodeGetNumPrecSolves", 1);
  retval = CVodeGetNumLinConvFails(cvode_mem, &ncfl);
  check_retval(&retval, "CVodeGetNumLinConvFails", 1);
  retval = CVodeGetNumLinRhsEvals(cvode_mem, &nfeLS);
  check_retval(&retval, "CVodeGetNumLinRhsEvals", 1);

  retval = CVBandPrecGetWorkSpace(cvode_mem, &lenrwBP, &leniwBP);
  check_retval(&retval, "CVBandPrecGetWorkSpace", 1);
  retval = CVBandPrecGetNumRhsEvals(cvode_mem, &nfeBP);
  check_retval(&retval, "CVBandPrecGetNumRhsEvals", 1);

  printf("\nFinal Statistics.. \n\n");
  printf("lenrw   = %5ld     leniw   = %5ld\n", lenrw, leniw);
  printf("lenrwls = %5ld     leniwls = %5ld\n", lenrwLS, leniwLS);
  printf("lenrwbp = %5ld     leniwbp = %5ld\n", lenrwBP, leniwBP);
  printf("nst     = %5ld\n", nst);
  printf("nfe     = %5ld     nfetot  = %5ld\n", nfe, nfe + nfeLS + nfeBP);
  printf("nfeLS   = %5ld     nfeBP   = %5ld\n", nfeLS, nfeBP);
  printf("nni     = %5ld     nli     = %5ld\n", nni, nli);
  printf("nsetups = %5ld     netf    = %5ld\n", nsetups, netf);
  printf("npe     = %5ld     nps     = %5ld\n", npe, nps);
  printf("ncfn    = %5ld     ncfl    = %5ld\n\n", ncfn, ncfl);
}

/* Check function return value...
     opt == 0 means SUNDIALS function allocates memory so check if
              returned NULL pointer
     opt == 1 means SUNDIALS function returns an integer value so check if
              retval < 0
     opt == 2 means function allocates memory so check if returned
              NULL pointer */

static int check_retval(void* returnvalue, const char* funcname, int opt)
{
  int* retval;

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

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

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

  return (0);
}

/*
 *-------------------------------
 * Function called by the solver
 *-------------------------------
 */

/* f routine. Compute f(t,u). */

static int f(sunrealtype t, N_Vector u, N_Vector udot, void* user_data)
{
  sunrealtype q3, c1, c2, c1dn, c2dn, c1up, c2up, c1lt, c2lt;
  sunrealtype c1rt, c2rt, cydn, cyup, hord1, hord2, horad1, horad2;
  sunrealtype qq1, qq2, qq3, qq4, rkin1, rkin2, s, vertd1, vertd2, ydn, yup;
  sunrealtype q4coef, dely, verdco, hordco, horaco;
  sunrealtype *udata, *dudata;
  int idn, iup, ileft, iright, jx, jy;
  UserData data;

  data   = (UserData)user_data;
  udata  = N_VGetArrayPointer(u);
  dudata = N_VGetArrayPointer(udot);

  /* Set diurnal rate coefficients. */

  s = sin(data->om * t);
  if (s > ZERO)
  {
    q3       = exp(-A3 / s);
    data->q4 = exp(-A4 / s);
  }
  else
  {
    q3       = ZERO;
    data->q4 = ZERO;
  }

  /* Make local copies of problem variables, for efficiency. */

  q4coef = data->q4;
  dely   = data->dy;
  verdco = data->vdco;
  hordco = data->hdco;
  horaco = data->haco;

  /* Loop over all grid points. */

  for (jy = 0; jy < MY; jy++)
  {
    /* Set vertical diffusion coefficients at jy +- 1/2 */

    ydn  = YMIN + (jy - SUN_RCONST(0.5)) * dely;
    yup  = ydn + dely;
    cydn = verdco * exp(SUN_RCONST(0.2) * ydn);
    cyup = verdco * exp(SUN_RCONST(0.2) * yup);
    idn  = (jy == 0) ? 1 : -1;
    iup  = (jy == MY - 1) ? -1 : 1;
    for (jx = 0; jx < MX; jx++)
    {
      /* Extract c1 and c2, and set kinetic rate terms. */

      c1    = IJKth(udata, 1, jx, jy);
      c2    = IJKth(udata, 2, jx, jy);
      qq1   = Q1 * c1 * C3;
      qq2   = Q2 * c1 * c2;
      qq3   = q3 * C3;
      qq4   = q4coef * c2;
      rkin1 = -qq1 - qq2 + TWO * qq3 + qq4;
      rkin2 = qq1 - qq2 - qq4;

      /* Set vertical diffusion terms. */

      c1dn   = IJKth(udata, 1, jx, jy + idn);
      c2dn   = IJKth(udata, 2, jx, jy + idn);
      c1up   = IJKth(udata, 1, jx, jy + iup);
      c2up   = IJKth(udata, 2, jx, jy + iup);
      vertd1 = cyup * (c1up - c1) - cydn * (c1 - c1dn);
      vertd2 = cyup * (c2up - c2) - cydn * (c2 - c2dn);

      /* Set horizontal diffusion and advection terms. */

      ileft  = (jx == 0) ? 1 : -1;
      iright = (jx == MX - 1) ? -1 : 1;
      c1lt   = IJKth(udata, 1, jx + ileft, jy);
      c2lt   = IJKth(udata, 2, jx + ileft, jy);
      c1rt   = IJKth(udata, 1, jx + iright, jy);
      c2rt   = IJKth(udata, 2, jx + iright, jy);
      hord1  = hordco * (c1rt - TWO * c1 + c1lt);
      hord2  = hordco * (c2rt - TWO * c2 + c2lt);
      horad1 = horaco * (c1rt - c1lt);
      horad2 = horaco * (c2rt - c2lt);

      /* Load all terms into udot. */

      IJKth(dudata, 1, jx, jy) = vertd1 + hord1 + horad1 + rkin1;
      IJKth(dudata, 2, jx, jy) = vertd2 + hord2 + horad2 + rkin2;
    }
  }

  return (0);
}
