/*
 * -----------------------------------------------------------------
 * $Revision: 1.3 $
 * $Date: 2007/04/30 19:29:00 $
 * -----------------------------------------------------------------
 * Programmers: Alan C. Hindmarsh, and Radu Serban @ LLNL
 * -----------------------------------------------------------------
 * Copyright (c) 2002, The Regents of the University of California
 * Produced at the Lawrence Livermore National Laboratory
 * All rights reserved
 * For details, see the LICENSE file
 * -----------------------------------------------------------------
 * This is the implementation file for the IC calculation for IDA.
 * It is independent of the linear solver in use.
 * -----------------------------------------------------------------
 */

#include <stdio.h>
#include <stdlib.h>

#include "ida_impl.h"
#include <sundials/sundials_math.h>

/* SUNDIALS EXTENSION */
#include "sundials/sundials_extension.h"

/* Macro: loop */
#define loop for(;;)

/*
 * =================================================================
 * IDA Constants
 * =================================================================
 */

/* Private Constants */

#define ZERO       RCONST(0.0)    /* real 0.0    */
#define HALF       RCONST(0.5)    /* real 0.5    */
#define ONE        RCONST(1.0)    /* real 1.0    */
#define TWO        RCONST(2.0)    /* real 2.0    */
#define PT99       RCONST(0.99)   /* real 0.99   */
#define PT1        RCONST(0.1)    /* real 0.1    */
#define PT001      RCONST(0.001)  /* real 0.001  */

/* IDACalcIC control constants */

#define ICRATEMAX  RCONST(0.9)    /* max. Newton conv. rate */
#define ALPHALS    RCONST(0.0001) /* alpha in linesearch conv. test */

/* Return values for lower level routines used by IDACalcIC */

#define IC_FAIL_RECOV       1
#define IC_CONSTR_FAILED    2
#define IC_LINESRCH_FAILED  3
#define IC_CONV_FAIL        4
#define IC_SLOW_CONVRG      5

/*
 * =================================================================
 * Private Helper Functions Prototypes
 * =================================================================
 */

extern int IDAInitialSetup(IDAMem IDA_mem);
extern realtype IDAWrmsNorm(IDAMem IDA_mem, N_Vector x, N_Vector w,
                            booleantype mask);

static int IDAnlsIC(IDAMem IDA_mem);
static int IDANewtonIC(IDAMem IDA_mem);
static int IDALineSrch(IDAMem IDA_mem, realtype *delnorm, realtype *fnorm);
static int IDAfnorm(IDAMem IDA_mem, realtype *fnorm);
static int IDANewyyp(IDAMem IDA_mem, realtype lambda);
static int IDANewy(IDAMem IDA_mem);
static int IDAICFailFlag(IDAMem IDA_mem, int retval);

/*
 * =================================================================
 * Readibility Constants
 * =================================================================
 */

#define t0             (IDA_mem->ida_t0)
#define yy0            (IDA_mem->ida_yy0)
#define yp0            (IDA_mem->ida_yp0)

#define user_data      (IDA_mem->ida_user_data)
#define res            (IDA_mem->ida_res)
#define efun           (IDA_mem->ida_efun)
#define edata          (IDA_mem->ida_edata)
#define uround         (IDA_mem->ida_uround)
#define phi            (IDA_mem->ida_phi)
#define ewt            (IDA_mem->ida_ewt)
#define delta          (IDA_mem->ida_delta)
#define ee             (IDA_mem->ida_ee)
#define savres         (IDA_mem->ida_savres)
#define tempv2         (IDA_mem->ida_tempv2)
#define hh             (IDA_mem->ida_hh)
#define tn             (IDA_mem->ida_tn)
#define cj             (IDA_mem->ida_cj)
#define cjratio        (IDA_mem->ida_cjratio)
#define nbacktr        (IDA_mem->ida_nbacktr)
#define nre            (IDA_mem->ida_nre)
#define ncfn           (IDA_mem->ida_ncfn)
#define nni            (IDA_mem->ida_nni)
#define nsetups        (IDA_mem->ida_nsetups)
#define ns             (IDA_mem->ida_ns)
#define lsetup         (IDA_mem->ida_lsetup)
#define lsolve         (IDA_mem->ida_lsolve)
#define hused          (IDA_mem->ida_hused)
#define epsNewt        (IDA_mem->ida_epsNewt)
#define id             (IDA_mem->ida_id)
#define setupNonNull   (IDA_mem->ida_setupNonNull)
#define suppressalg    (IDA_mem->ida_suppressalg)
#define constraints    (IDA_mem->ida_constraints)
#define constraintsSet (IDA_mem->ida_constraintsSet)

#define epiccon  (IDA_mem->ida_epiccon)
#define maxnh    (IDA_mem->ida_maxnh)
#define maxnj    (IDA_mem->ida_maxnj)
#define maxnit   (IDA_mem->ida_maxnit)
#define lsoff    (IDA_mem->ida_lsoff)
#define steptol  (IDA_mem->ida_steptol)

/*
 * =================================================================
 * EXPORTED FUNCTIONS IMPLEMENTATION
 * =================================================================
 */

/*
 * -----------------------------------------------------------------
 * IDACalcIC
 * -----------------------------------------------------------------
 * IDACalcIC computes consistent initial conditions, given the
 * user's initial guess for unknown components of yy0 and/or yp0.
 *
 * The return value is IDA_SUCCESS = 0 if no error occurred.
 *
 * The error return values (fully described in ida.h) are:
 *   IDA_MEM_NULL        ida_mem is NULL
 *   IDA_NO_MALLOC       ida_mem was not allocated
 *   IDA_ILL_INPUT       bad value for icopt, tout1, or id
 *   IDA_LINIT_FAIL      the linear solver linit routine failed
 *   IDA_BAD_EWT         zero value of some component of ewt
 *   IDA_RES_FAIL        res had a non-recoverable error
 *   IDA_FIRST_RES_FAIL  res failed recoverably on the first call
 *   IDA_LSETUP_FAIL     lsetup had a non-recoverable error
 *   IDA_LSOLVE_FAIL     lsolve had a non-recoverable error
 *   IDA_NO_RECOVERY     res, lsetup, or lsolve had a recoverable
 *                       error, but IDACalcIC could not recover
 *   IDA_CONSTR_FAIL     the inequality constraints could not be met
 *   IDA_LINESEARCH_FAIL the linesearch failed (on steptol test)
 *   IDA_CONV_FAIL       the Newton iterations failed to converge
 * -----------------------------------------------------------------
 */

int IDACalcIC(void *ida_mem, int icopt, realtype tout1)
{
    int ewtsetOK;
    int ier, nwt, nh, mxnh, icret, retval = 0;
    realtype tdist, troundoff, minid, hic, ypnorm;
    IDAMem IDA_mem;

    /* Check if IDA memory exists */

    if (ida_mem == NULL)
    {
        IDAProcessError(NULL, IDA_MEM_NULL, "IDA", "IDACalcIC", MSG_NO_MEM);
        return(IDA_MEM_NULL);
    }
    IDA_mem = (IDAMem) ida_mem;

    /* Check if problem was malloc'ed */

    if (IDA_mem->ida_MallocDone == FALSE)
    {
        IDAProcessError(IDA_mem, IDA_NO_MALLOC, "IDA", "IDACalcIC", MSG_NO_MALLOC);
        return(IDA_NO_MALLOC);
    }

    /* Check inputs to IDA for correctness and consistency */

    ier = IDAInitialSetup(IDA_mem);
    if (ier != IDA_SUCCESS)
    {
        return(IDA_ILL_INPUT);
    }
    IDA_mem->ida_SetupDone = TRUE;

    /* Check legality of input arguments, and set IDA memory copies. */

    if (icopt != IDA_YA_YDP_INIT && icopt != IDA_Y_INIT)
    {
        IDAProcessError(IDA_mem, IDA_ILL_INPUT, "IDA", "IDACalcIC", MSG_IC_BAD_ICOPT);
        return(IDA_ILL_INPUT);
    }
    IDA_mem->ida_icopt = icopt;

    if (icopt == IDA_YA_YDP_INIT && (id == NULL))
    {
        IDAProcessError(IDA_mem, IDA_ILL_INPUT, "IDA", "IDACalcIC", MSG_IC_MISSING_ID);
        return(IDA_ILL_INPUT);
    }

    tdist = ABS(tout1 - tn);
    troundoff = TWO * uround * (ABS(tn) + ABS(tout1));
    if (tdist < troundoff)
    {
        IDAProcessError(IDA_mem, IDA_ILL_INPUT, "IDA", "IDACalcIC", MSG_IC_TOO_CLOSE);
        return(IDA_ILL_INPUT);
    }

    /* Allocate space and initialize temporary vectors */

    yy0 = N_VClone(ee);
    yp0 = N_VClone(ee);
    t0  = tn;
    N_VScale(ONE, phi[0], yy0);
    N_VScale(ONE, phi[1], yp0);

    /* For use in the IDA_YA_YP_INIT case, set sysindex and tscale. */

    IDA_mem->ida_sysindex = 1;
    IDA_mem->ida_tscale   = tdist;
    if (icopt == IDA_YA_YDP_INIT)
    {
        minid = N_VMin(id);
        if (minid < ZERO)
        {
            IDAProcessError(IDA_mem, IDA_ILL_INPUT, "IDA", "IDACalcIC", MSG_IC_BAD_ID);
            return(IDA_ILL_INPUT);
        }
        if (minid > HALF)
        {
            IDA_mem->ida_sysindex = 0;
        }
    }

    /* Set the test constant in the Newton convergence test */

    IDA_mem->ida_epsNewt = epiccon;

    /* Initializations:
       cjratio = 1 (for use in direct linear solvers);
       set nbacktr = 0; */

    cjratio = ONE;
    nbacktr = 0;

    /* Set hic, hh, cj, and mxnh. */

    hic = PT001 * tdist;
    ypnorm = IDAWrmsNorm(IDA_mem, yp0, ewt, suppressalg);
    if (ypnorm > HALF / hic)
    {
        hic = HALF / ypnorm;
    }
    if (tout1 < tn)
    {
        hic = -hic;
    }
    hh = hic;
    if (icopt == IDA_YA_YDP_INIT)
    {
        cj = ONE / hic;
        mxnh = maxnh;
    }
    else
    {
        cj = ZERO;
        mxnh = 1;
    }

    /* Loop over nwt = number of evaluations of ewt vector. */

    for (nwt = 1; nwt <= 2; nwt++)
    {

        /* Loop over nh = number of h values. */
        for (nh = 1; nh <= mxnh; nh++)
        {

            /* Call the IC nonlinear solver function. */
            retval = IDAnlsIC(IDA_mem);

            /* Cut h and loop on recoverable IDA_YA_YDP_INIT failure; else break. */
            if (retval == IDA_SUCCESS)
            {
                break;
            }
            ncfn++;
            if (retval < 0)
            {
                break;
            }
            if (nh == mxnh)
            {
                break;
            }
            /* If looping to try again, reset yy0 and yp0 if not converging. */
            if (retval != IC_SLOW_CONVRG)
            {
                N_VScale(ONE, phi[0], yy0);
                N_VScale(ONE, phi[1], yp0);
            }
            hic *= PT1;
            cj = ONE / hic;
            hh = hic;
        }   /* End of nh loop */

        /* Break on failure; else reset ewt, save yy0, yp0 in phi, and loop. */
        if (retval != IDA_SUCCESS)
        {
            break;
        }
        ewtsetOK = efun(yy0, ewt, edata);
        if (ewtsetOK != 0)
        {
            retval = IDA_BAD_EWT;
            break;
        }
        N_VScale(ONE, yy0, phi[0]);
        N_VScale(ONE, yp0, phi[1]);

    }   /* End of nwt loop */

    /* Free temporary space */

    /* SUNDIALS EXTENSION */
    if (is_sundials_with_extension())
    {
        /* in order to return computed new values even if they are not consistent*/
        N_VScale(ONE, yy0, phi[0]);
        N_VScale(ONE, yp0, phi[1]);
    }

    N_VDestroy(yy0);
    N_VDestroy(yp0);

    /* Load the optional outputs. */

    if (icopt == IDA_YA_YDP_INIT)
    {
        hused = hic;
    }

    /* On any failure, print message and return proper flag. */

    if (retval != IDA_SUCCESS)
    {
        icret = IDAICFailFlag(IDA_mem, retval);
        return(icret);
    }

    /* Otherwise return success flag. */

    return(IDA_SUCCESS);

}

/*
 * =================================================================
 * PRIVATE FUNCTIONS IMPLEMENTATION
 * =================================================================
 */

#define icopt    (IDA_mem->ida_icopt)
#define sysindex (IDA_mem->ida_sysindex)
#define tscale   (IDA_mem->ida_tscale)
#define ynew     (IDA_mem->ida_ynew)
#define ypnew    (IDA_mem->ida_ypnew)
#define delnew   (IDA_mem->ida_delnew)
#define dtemp    (IDA_mem->ida_dtemp)

/*
 * -----------------------------------------------------------------
 * IDAnlsIC
 * -----------------------------------------------------------------
 * IDAnlsIC solves a nonlinear system for consistent initial
 * conditions.  It calls IDANewtonIC to do most of the work.
 *
 * The return value is IDA_SUCCESS = 0 if no error occurred.
 * The error return values (positive) considered recoverable are:
 *  IC_FAIL_RECOV      if res, lsetup, or lsolve failed recoverably
 *  IC_CONSTR_FAILED   if the constraints could not be met
 *  IC_LINESRCH_FAILED if the linesearch failed (on steptol test)
 *  IC_CONV_FAIL       if the Newton iterations failed to converge
 *  IC_SLOW_CONVRG     if the iterations are converging slowly
 *                     (failed the convergence test, but showed
 *                     norm reduction or convergence rate < 1)
 * The error return values (negative) considered non-recoverable are:
 *  IDA_RES_FAIL       if res had a non-recoverable error
 *  IDA_FIRST_RES_FAIL if res failed recoverably on the first call
 *  IDA_LSETUP_FAIL    if lsetup had a non-recoverable error
 *  IDA_LSOLVE_FAIL    if lsolve had a non-recoverable error
 * -----------------------------------------------------------------
 */

static int IDAnlsIC (IDAMem IDA_mem)
{
    int retval, nj;
    N_Vector tv1, tv2, tv3;

    tv1 = ee;
    tv2 = tempv2;
    tv3 = phi[2];

    retval = res(t0, yy0, yp0, delta, user_data);
    nre++;
    if (retval < 0)
    {
        return(IDA_RES_FAIL);
    }
    if (retval > 0)
    {
        return(IDA_FIRST_RES_FAIL);
    }

    N_VScale(ONE, delta, savres);

    /* Loop over nj = number of linear solve Jacobian setups. */

    for (nj = 1; nj <= maxnj; nj++)
    {

        /* If there is a setup routine, call it. */
        if (setupNonNull)
        {
            nsetups++;
            retval = lsetup(IDA_mem, yy0, yp0, delta, tv1, tv2, tv3);
            if (retval < 0)
            {
                return(IDA_LSETUP_FAIL);
            }
            if (retval > 0)
            {
                return(IC_FAIL_RECOV);
            }
        }

        /* Call the Newton iteration routine, and return if successful.  */
        retval = IDANewtonIC(IDA_mem);
        if (retval == IDA_SUCCESS)
        {
            return(IDA_SUCCESS);
        }

        /* If converging slowly and lsetup is nontrivial, retry. */
        if (retval == IC_SLOW_CONVRG && setupNonNull)
        {
            N_VScale(ONE, savres, delta);
            continue;
        }
        else
        {
            return(retval);
        }

    }   /* End of nj loop */

    /* No convergence after maxnj tries; return with retval=IC_SLOW_CONVRG */
    return(retval);

}

/*
 * -----------------------------------------------------------------
 * IDANewtonIC
 * -----------------------------------------------------------------
 * IDANewtonIC performs the Newton iteration to solve for consistent
 * initial conditions.  It calls IDALineSrch within each iteration.
 * On return, savres contains the current residual vector.
 *
 * The return value is IDA_SUCCESS = 0 if no error occurred.
 * The error return values (positive) considered recoverable are:
 *  IC_FAIL_RECOV      if res or lsolve failed recoverably
 *  IC_CONSTR_FAILED   if the constraints could not be met
 *  IC_LINESRCH_FAILED if the linesearch failed (on steptol test)
 *  IC_CONV_FAIL       if the Newton iterations failed to converge
 *  IC_SLOW_CONVRG     if the iterations appear to be converging slowly.
 *                     They failed the convergence test, but showed
 *                     an overall norm reduction (by a factor of < 0.1)
 *                     or a convergence rate <= ICRATEMAX).
 * The error return values (negative) considered non-recoverable are:
 *  IDA_RES_FAIL   if res had a non-recoverable error
 *  IDA_LSOLVE_FAIL      if lsolve had a non-recoverable error
 * -----------------------------------------------------------------
 */

static int IDANewtonIC(IDAMem IDA_mem)
{
    int retval, mnewt;
    realtype delnorm, fnorm, fnorm0, oldfnrm, rate;

    /* Set pointer for vector delnew */
    delnew = phi[2];

    /* Call the linear solve function to get the Newton step, delta. */
    retval = lsolve(IDA_mem, delta, ewt, yy0, yp0, savres);
    if (retval < 0)
    {
        return(IDA_LSOLVE_FAIL);
    }
    if (retval > 0)
    {
        return(IC_FAIL_RECOV);
    }

    /* Compute the norm of the step; return now if this is small. */
    fnorm = IDAWrmsNorm(IDA_mem, delta, ewt, FALSE);
    if (sysindex == 0)
    {
        fnorm *= tscale * ABS(cj);
    }
    if (fnorm <= epsNewt)
    {
        return(IDA_SUCCESS);
    }
    fnorm0 = fnorm;

    /* Initialize rate to avoid compiler warning message */
    rate = ZERO;

    /* Newton iteration loop */

    for (mnewt = 0; mnewt < maxnit; mnewt++)
    {

        nni++;
        delnorm = fnorm;
        oldfnrm = fnorm;

        /* Call the Linesearch function and return if it failed. */
        retval = IDALineSrch(IDA_mem, &delnorm, &fnorm);
        if (retval != IDA_SUCCESS)
        {
            return(retval);
        }

        /* Set the observed convergence rate and test for convergence. */
        rate = fnorm / oldfnrm;
        if (fnorm <= epsNewt)
        {
            return(IDA_SUCCESS);
        }

        /* If not converged, copy new step vector, and loop. */
        N_VScale(ONE, delnew, delta);

    }   /* End of Newton iteration loop */

    /* Return either IC_SLOW_CONVRG or recoverable fail flag. */
    if (rate <= ICRATEMAX || fnorm < PT1 * fnorm0)
    {
        return(IC_SLOW_CONVRG);
    }
    return(IC_CONV_FAIL);

}


/*
 * -----------------------------------------------------------------
 * IDALineSrch
 * -----------------------------------------------------------------
 * IDALineSrch performs the Linesearch algorithm with the
 * calculation of consistent initial conditions.
 *
 * On entry, yy0 and yp0 are the current values of y and y', the
 * Newton step is delta, the current residual vector F is savres,
 * delnorm is WRMS-norm(delta), and fnorm is the norm of the vector
 * J-inverse F.
 *
 * On a successful return, yy0, yp0, and savres have been updated,
 * delnew contains the current value of J-inverse F, and fnorm is
 * WRMS-norm(delnew).
 *
 * The return value is IDA_SUCCESS = 0 if no error occurred.
 * The error return values (positive) considered recoverable are:
 *  IC_FAIL_RECOV      if res or lsolve failed recoverably
 *  IC_CONSTR_FAILED   if the constraints could not be met
 *  IC_LINESRCH_FAILED if the linesearch failed (on steptol test)
 * The error return values (negative) considered non-recoverable are:
 *  IDA_RES_FAIL   if res had a non-recoverable error
 *  IDA_LSOLVE_FAIL      if lsolve had a non-recoverable error
 * -----------------------------------------------------------------
 */

static int IDALineSrch(IDAMem IDA_mem, realtype *delnorm, realtype *fnorm)
{
    booleantype conOK;
    int retval;
    realtype f1norm, fnormp, f1normp, ratio, lambda, minlam, slpi;
    N_Vector mc;

    /* Initialize work space pointers, f1norm, ratio.
       (Use of mc in constraint check does not conflict with ypnew.) */
    mc = ee;
    dtemp = phi[3];
    ynew = tempv2;
    ypnew = ee;
    f1norm = (*fnorm) * (*fnorm) * HALF;
    ratio = ONE;

    /* If there are constraints, check and reduce step if necessary. */
    if (constraintsSet)
    {

        /* Update y and check constraints. */
        IDANewy(IDA_mem);
        conOK = N_VConstrMask(constraints, ynew, mc);

        if (!conOK)
        {
            /* Not satisfied.  Compute scaled step to satisfy constraints. */
            N_VProd(mc, delta, dtemp);
            ratio = PT99 * N_VMinQuotient(yy0, dtemp);
            (*delnorm) *= ratio;
            if ((*delnorm) <= steptol)
            {
                return(IC_CONSTR_FAILED);
            }
            N_VScale(ratio, delta, delta);
        }

    } /* End of constraints check */

    slpi = -TWO * f1norm * ratio;
    minlam = steptol / (*delnorm);
    lambda = ONE;

    /* In IDA_Y_INIT case, set ypnew = yp0 (fixed) for linesearch. */
    if (icopt == IDA_Y_INIT)
    {
        N_VScale(ONE, yp0, ypnew);
    }

    /* Loop on linesearch variable lambda. */

    loop
    {

        /* Get new (y,y') = (ynew,ypnew) and norm of new function value. */
        IDANewyyp(IDA_mem, lambda);
        retval = IDAfnorm(IDA_mem, &fnormp);
        if (retval != IDA_SUCCESS)
        {
            return(retval);
        }

        /* If lsoff option is on, break out. */
        if (lsoff)
        {
            break;
        }

        /* Do alpha-condition test. */
        f1normp = fnormp * fnormp * HALF;
        if (f1normp <= f1norm + ALPHALS*slpi*lambda)
        {
            break;
        }
        if (lambda < minlam)
        {
            return(IC_LINESRCH_FAILED);
        }
        lambda /= TWO;
        nbacktr++;

    }  /* End of breakout linesearch loop */

    /* Update yy0, yp0, and fnorm, then return. */
    N_VScale(ONE, ynew,  yy0);
    if (icopt == IDA_YA_YDP_INIT)
    {
        N_VScale(ONE, ypnew, yp0);
    }
    *fnorm = fnormp;
    return(IDA_SUCCESS);

}

/*
 * -----------------------------------------------------------------
 * IDAfnorm
 * -----------------------------------------------------------------
 * IDAfnorm computes the norm of the current function value, by
 * evaluating the DAE residual function, calling the linear
 * system solver, and computing a WRMS-norm.
 *
 * On return, savres contains the current residual vector F, and
 * delnew contains J-inverse F.
 *
 * The return value is IDA_SUCCESS = 0 if no error occurred, or
 *  IC_FAIL_RECOV    if res or lsolve failed recoverably, or
 *  IDA_RES_FAIL     if res had a non-recoverable error, or
 *  IDA_LSOLVE_FAIL  if lsolve had a non-recoverable error.
 * -----------------------------------------------------------------
 */

static int IDAfnorm(IDAMem IDA_mem, realtype *fnorm)
{

    int retval;

    /* Get residual vector F, return if failed, and save F in savres. */
    retval = res(t0, ynew, ypnew, delnew, user_data);
    nre++;
    if (retval < 0)
    {
        return(IDA_RES_FAIL);
    }
    if (retval > 0)
    {
        return(IC_FAIL_RECOV);
    }

    N_VScale(ONE, delnew, savres);

    /* Call the linear solve function to get J-inverse F; return if failed. */
    retval = lsolve(IDA_mem, delnew, ewt, ynew, ypnew, savres);
    if (retval < 0)
    {
        return(IDA_LSOLVE_FAIL);
    }
    if (retval > 0)
    {
        return(IC_FAIL_RECOV);
    }

    /* Compute the WRMS-norm; rescale if index = 0. */
    *fnorm = IDAWrmsNorm(IDA_mem, delnew, ewt, FALSE);
    if (sysindex == 0)
    {
        (*fnorm) *= tscale * ABS(cj);
    }

    return(IDA_SUCCESS);

}

/*
 * -----------------------------------------------------------------
 * IDANewyyp
 * -----------------------------------------------------------------
 * IDANewyyp updates the vectors ynew and ypnew from yy0 and yp0,
 * using the current step vector lambda*delta, in a manner
 * depending on icopt and the input id vector.
 *
 * The return value is always IDA_SUCCESS = 0.
 * -----------------------------------------------------------------
 */

static int IDANewyyp(IDAMem IDA_mem, realtype lambda)
{

    /* IDA_YA_YDP_INIT case: ynew  = yy0 - lambda*delta    where id_i = 0
                             ypnew = yp0 - cj*lambda*delta where id_i = 1. */
    if (icopt == IDA_YA_YDP_INIT)
    {
        N_VProd(id, delta, dtemp);
        N_VLinearSum(ONE, yp0, -cj * lambda, dtemp, ypnew);
        N_VLinearSum(ONE, delta, -ONE, dtemp, dtemp);
        N_VLinearSum(ONE, yy0, -lambda, dtemp, ynew);
        return(IDA_SUCCESS);
    }

    /* IDA_Y_INIT case: ynew = yy0 - lambda*delta. (ypnew = yp0 preset.) */
    N_VLinearSum(ONE, yy0, -lambda, delta, ynew);
    return(IDA_SUCCESS);

}

/*
 * -----------------------------------------------------------------
 * IDANewy
 * -----------------------------------------------------------------
 * IDANewy updates the vector ynew from yy0,
 * using the current step vector delta, in a manner
 * depending on icopt and the input id vector.
 *
 * The return value is always IDA_SUCCESS = 0.
 * -----------------------------------------------------------------
 */

static int IDANewy(IDAMem IDA_mem)
{

    /* IDA_YA_YDP_INIT case: ynew = yy0 - delta    where id_i = 0. */
    if (icopt == IDA_YA_YDP_INIT)
    {
        N_VProd(id, delta, dtemp);
        N_VLinearSum(ONE, delta, -ONE, dtemp, dtemp);
        N_VLinearSum(ONE, yy0, -ONE, dtemp, ynew);
        return(IDA_SUCCESS);
    }

    /* IDA_Y_INIT case: ynew = yy0 - delta. */
    N_VLinearSum(ONE, yy0, -ONE, delta, ynew);
    return(IDA_SUCCESS);

}

/*
 * -----------------------------------------------------------------
 * IDAICFailFlag
 * -----------------------------------------------------------------
 * IDAICFailFlag prints a message and sets the IDACalcIC return
 * value appropriate to the flag retval returned by IDAnlsIC.
 * -----------------------------------------------------------------
 */

static int IDAICFailFlag(IDAMem IDA_mem, int retval)
{

    /* Depending on retval, print error message and return error flag. */
    switch (retval)
    {

        case IDA_RES_FAIL:
            IDAProcessError(IDA_mem, IDA_RES_FAIL, "IDA", "IDACalcIC", MSG_IC_RES_NONREC);
            return(IDA_RES_FAIL);

        case IDA_FIRST_RES_FAIL:
            IDAProcessError(IDA_mem, IDA_FIRST_RES_FAIL, "IDA", "IDACalcIC", MSG_IC_RES_FAIL);
            return(IDA_FIRST_RES_FAIL);

        case IDA_LSETUP_FAIL:
            IDAProcessError(IDA_mem, IDA_LSETUP_FAIL, "IDA", "IDACalcIC", MSG_IC_SETUP_FAIL);
            return(IDA_LSETUP_FAIL);

        case IDA_LSOLVE_FAIL:
            IDAProcessError(IDA_mem, IDA_LSOLVE_FAIL, "IDA", "IDACalcIC", MSG_IC_SOLVE_FAIL);
            return(IDA_LSOLVE_FAIL);

        case IC_FAIL_RECOV:
            IDAProcessError(IDA_mem, IDA_NO_RECOVERY, "IDA", "IDACalcIC", MSG_IC_NO_RECOVERY);
            return(IDA_NO_RECOVERY);

        case IC_CONSTR_FAILED:
            IDAProcessError(IDA_mem, IDA_CONSTR_FAIL, "IDA", "IDACalcIC", MSG_IC_FAIL_CONSTR);
            return(IDA_CONSTR_FAIL);

        case IC_LINESRCH_FAILED:
            IDAProcessError(IDA_mem, IDA_LINESEARCH_FAIL, "IDA", "IDACalcIC", MSG_IC_FAILED_LINS);
            return(IDA_LINESEARCH_FAIL);

        case IC_CONV_FAIL:
            IDAProcessError(IDA_mem, IDA_CONV_FAIL, "IDA", "IDACalcIC", MSG_IC_CONV_FAILED);
            return(IDA_CONV_FAIL);

        case IC_SLOW_CONVRG:
            IDAProcessError(IDA_mem, IDA_CONV_FAIL, "IDA", "IDACalcIC", MSG_IC_CONV_FAILED);
            return(IDA_CONV_FAIL);

        case IDA_BAD_EWT:
            IDAProcessError(IDA_mem, IDA_BAD_EWT, "IDA", "IDACalcIC", MSG_IC_BAD_EWT);
            return(IDA_BAD_EWT);

    }
    return -99;
}

