/*
 *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *<LicenseText>
 *
 * CitcomS by Louis Moresi, Shijie Zhong, Lijie Han, Eh Tan,
 * Clint Conrad, Michael Gurnis, and Eun-seo Choi.
 * Copyright (C) 1994-2005, California Institute of Technology.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *</LicenseText>
 *
 *~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */
/* Functions relating to the determination of viscosity field either
   as a function of the run, as an initial condition or as specified from
   a previous file */


#include <math.h>
#include <sys/types.h>
#include "element_definitions.h"
#include "global_defs.h"
#include "parsing.h"


void myerror(struct All_variables *,char *);

static void apply_low_visc_wedge_channel(struct All_variables *E, float **evisc);
static void low_viscosity_channel_factor(struct All_variables *E, float *F);
static void low_viscosity_wedge_factor(struct All_variables *E, float *F);


void viscosity_system_input(struct All_variables *E)
{
    int m=E->parallel.me;
    int i;

    /* default values .... */
    for(i=0;i<40;i++) {
        E->viscosity.N0[i]=1.0;
        E->viscosity.T[i] = 0.0;
        E->viscosity.Z[i] = 0.0;
        E->viscosity.E[i] = 0.0;

	E->viscosity.pdepv_a[i] = 1.e20; /* \sigma_y = min(a + b * (1-r),y) */
	E->viscosity.pdepv_b[i] = 0.0;
	E->viscosity.pdepv_y[i] = 1.e20;


    }
    for(i=0;i<10;i++)
      E->viscosity.cdepv_ff[i] = 1.0; /* flavor factors for CDEPV */


    /* read in information */
    input_boolean("VISC_UPDATE",&(E->viscosity.update_allowed),"on",m);
    input_int("rheol",&(E->viscosity.RHEOL),"3",m);
    input_int("num_mat",&(E->viscosity.num_mat),"1",m);
    input_float_vector("visc0",E->viscosity.num_mat,(E->viscosity.N0),m);

    input_boolean("TDEPV",&(E->viscosity.TDEPV),"on",m);
    if (E->viscosity.TDEPV) {
        input_float_vector("viscT",E->viscosity.num_mat,(E->viscosity.T),m);
        input_float_vector("viscE",E->viscosity.num_mat,(E->viscosity.E),m);
        input_float_vector("viscZ",E->viscosity.num_mat,(E->viscosity.Z),m);
    }


    E->viscosity.sdepv_misfit = 1.0;
    input_boolean("SDEPV",&(E->viscosity.SDEPV),"off",m);
    if (E->viscosity.SDEPV) {
      E->viscosity.pdepv_visited = 0;
      input_float_vector("sdepv_expt",E->viscosity.num_mat,(E->viscosity.sdepv_expt),m);
    }


    input_boolean("PDEPV",&(E->viscosity.PDEPV),"off",m); /* plasticity addition by TWB */
    if (E->viscosity.PDEPV) {
      E->viscosity.pdepv_visited = 0;

      input_boolean("pdepv_eff",&(E->viscosity.pdepv_eff),"on",m);
      input_float_vector("pdepv_a",E->viscosity.num_mat,(E->viscosity.pdepv_a),m);
      input_float_vector("pdepv_b",E->viscosity.num_mat,(E->viscosity.pdepv_b),m);
      input_float_vector("pdepv_y",E->viscosity.num_mat,(E->viscosity.pdepv_y),m);

      input_float("pdepv_offset",&(E->viscosity.pdepv_offset),"0.0",m);
    }
    if(E->viscosity.PDEPV || E->viscosity.SDEPV)
      input_float("sdepv_misfit",&(E->viscosity.sdepv_misfit),"0.001",m);


    input_boolean("CDEPV",&(E->viscosity.CDEPV),"off",m);
    if(E->viscosity.CDEPV){	/* compositional viscosity */
      if(!E->control.tracer)
	myerror(E,"error: CDEPV requires tracers, but tracer is off");
      if(E->trace.nflavors > 10)
	myerror(E,"error: too many flavors for CDEPV");
      /* read in flavor factors */
      input_float_vector("cdepv_ff",E->trace.nflavors,
			 (E->viscosity.cdepv_ff),m);
      /* and take the log because we're using a geometric avg */
      for(i=0;i<E->trace.nflavors;i++)
	E->viscosity.cdepv_ff[i] = log(E->viscosity.cdepv_ff[i]);
    }


    input_boolean("low_visc_channel",&(E->viscosity.channel),"off",m);
    input_boolean("low_visc_wedge",&(E->viscosity.wedge),"off",m);

    input_float("lv_min_radius",&(E->viscosity.lv_min_radius),"0.9764",m);
    input_float("lv_max_radius",&(E->viscosity.lv_max_radius),"0.9921",m);
    input_float("lv_channel_thickness",&(E->viscosity.lv_channel_thickness),"0.0047",m);
    input_float("lv_reduction",&(E->viscosity.lv_reduction),"0.5",m);

    input_boolean("VMAX",&(E->viscosity.MAX),"off",m);
    if (E->viscosity.MAX)
        input_float("visc_max",&(E->viscosity.max_value),"1e22,1,nomax",m);

    input_boolean("VMIN",&(E->viscosity.MIN),"off",m);
    if (E->viscosity.MIN)
        input_float("visc_min",&(E->viscosity.min_value),"1e20",m);

    return;
}


void viscosity_input(struct All_variables *E)
{
    int m = E->parallel.me;

    input_string("Viscosity",E->viscosity.STRUCTURE,"system",m);
    input_int ("visc_smooth_method",&(E->viscosity.smooth_cycles),"0",m);

    if ( strcmp(E->viscosity.STRUCTURE,"system") == 0)
        E->viscosity.FROM_SYSTEM = 1;
    else
        E->viscosity.FROM_SYSTEM = 0;

    if (E->viscosity.FROM_SYSTEM)
        viscosity_system_input(E);

    return;
}



/* ============================================ */

void get_system_viscosity(E,propogate,evisc,visc)
     struct All_variables *E;
     int propogate;
     float **evisc,**visc;
{
    void visc_from_mat();
    void visc_from_T();
    void visc_from_S();

    void visc_from_P();
    void visc_from_C();

    void apply_viscosity_smoother();
    void visc_from_gint_to_nodes();



    int i,j,m;
    float temp1,temp2,*vvvis;
    double *TG;

    const int vpts = vpoints[E->mesh.nsd];

    if(E->viscosity.TDEPV)
        visc_from_T(E,evisc,propogate);
    else
        visc_from_mat(E,evisc);

    if(E->viscosity.CDEPV)	/* compositional prefactor */
      visc_from_C(E,evisc);

    if(E->viscosity.SDEPV)
      visc_from_S(E,evisc,propogate);

    if(E->viscosity.PDEPV)	/* "plasticity" */
      visc_from_P(E,evisc);


    /* i think this should me placed differently i.e.  before the
       stress dependence but I won't change it because it's by
       someone else

       TWB
    */
    if(E->viscosity.channel || E->viscosity.wedge)
        apply_low_visc_wedge_channel(E, evisc);


    /* min/max cut-off */

    if(E->viscosity.MAX) {
        for(m=1;m<=E->sphere.caps_per_proc;m++)
            for(i=1;i<=E->lmesh.nel;i++)
                for(j=1;j<=vpts;j++)
                    if(evisc[m][(i-1)*vpts + j] > E->viscosity.max_value)
                        evisc[m][(i-1)*vpts + j] = E->viscosity.max_value;
    }

    if(E->viscosity.MIN) {
        for(m=1;m<=E->sphere.caps_per_proc;m++)
            for(i=1;i<=E->lmesh.nel;i++)
                for(j=1;j<=vpts;j++)
                    if(evisc[m][(i-1)*vpts + j] < E->viscosity.min_value)
                        evisc[m][(i-1)*vpts + j] = E->viscosity.min_value;
    }

    if (E->control.verbose)  {
      fprintf(E->fp_out,"output_evisc \n");
      for(m=1;m<=E->sphere.caps_per_proc;m++) {
        fprintf(E->fp_out,"output_evisc for cap %d\n",E->sphere.capid[m]);
      for(i=1;i<=E->lmesh.nel;i++)
          fprintf(E->fp_out,"%d %d %f %f\n",i,E->mat[m][i],evisc[m][(i-1)*vpts+1],evisc[m][(i-1)*vpts+7]);
      }
      fflush(E->fp_out);
    }

    /* interpolate from gauss quadrature points to node points for output */
    visc_from_gint_to_nodes(E,evisc,visc,E->mesh.levmax);

    return;
}



void initial_viscosity(struct All_variables *E)
{
    if (E->viscosity.FROM_SYSTEM)
        get_system_viscosity(E,1,E->EVI[E->mesh.levmax],E->VI[E->mesh.levmax]);

    return;
}


void visc_from_mat(E,EEta)
     struct All_variables *E;
     float **EEta;
{

    int i,m,jj;

    for(m=1;m<=E->sphere.caps_per_proc;m++)
        for(i=1;i<=E->lmesh.nel;i++)
            for(jj=1;jj<=vpoints[E->mesh.nsd];jj++)
                EEta[m][ (i-1)*vpoints[E->mesh.nsd]+jj ]=E->viscosity.N0[E->mat[m][i]-1];

    return;
}

void visc_from_T(E,EEta,propogate)
     struct All_variables *E;
     float **EEta;
     int propogate;
{
    int m,i,j,k,l,z,jj,kk,imark;
    float zero,e_6,one,eta0,Tave,depth,temp,tempa,temp1,TT[9];
    float zzz,zz[9];
    float visc1, visc2, tempa_exp;
    const int vpts = vpoints[E->mesh.nsd];
    const int ends = enodes[E->mesh.nsd];
    const int nel = E->lmesh.nel;

    e_6 = 1.e-6;
    one = 1.0;
    zero = 0.0;
    imark = 0;

    switch (E->viscosity.RHEOL)   {
    case 1:			/* eta = N_0 exp( E * (T_0 - T))  */
        for(m=1;m<=E->sphere.caps_per_proc;m++)
            for(i=1;i<=nel;i++)   {
                l = E->mat[m][i];

                if(E->control.mat_control==0)
                    tempa = E->viscosity.N0[l-1];
                else if(E->control.mat_control==1)
                    tempa = E->viscosity.N0[l-1]*E->VIP[m][i];

                for(kk=1;kk<=ends;kk++) {
                    TT[kk] = E->T[m][E->ien[m][i].node[kk]];
                }

                for(jj=1;jj<=vpts;jj++) {
                    temp=0.0;
                    for(kk=1;kk<=ends;kk++)   {
                        temp += TT[kk] * E->N.vpt[GNVINDEX(kk,jj)];
                    }

                    EEta[m][ (i-1)*vpts + jj ] = tempa*
                        exp( E->viscosity.E[l-1] * (E->viscosity.T[l-1] - temp));

                }
            }
        break;

    case 2:			/* eta = N_0 exp(-T/T_0) */
        for(m=1;m<=E->sphere.caps_per_proc;m++)
            for(i=1;i<=nel;i++)   {
                l = E->mat[m][i];

                if(E->control.mat_control==0)
                    tempa = E->viscosity.N0[l-1];
                else if(E->control.mat_control==1)
                    tempa = E->viscosity.N0[l-1]*E->VIP[m][i];

                for(kk=1;kk<=ends;kk++) {
                    TT[kk] = E->T[m][E->ien[m][i].node[kk]];
                }

                for(jj=1;jj<=vpts;jj++) {
                    temp=0.0;
                    for(kk=1;kk<=ends;kk++)   {
                        temp += TT[kk] * E->N.vpt[GNVINDEX(kk,jj)];
                    }

                    EEta[m][ (i-1)*vpts + jj ] = tempa*
                        exp( -temp / E->viscosity.T[l-1]);

                }
            }
        break;

    case 3:			/* eta = N_0 exp(E/(T+T_0) - E/(1+T_0)) */

        for(m=1;m<=E->sphere.caps_per_proc;m++)
            for(i=1;i<=nel;i++)   {
                l = E->mat[m][i];
		if(E->control.mat_control) /* switch moved up here TWB */
		  tempa = E->viscosity.N0[l-1] * E->VIP[m][i];
		else
		  tempa = E->viscosity.N0[l-1];
                j = 0;

                for(kk=1;kk<=ends;kk++) {
		  TT[kk] = E->T[m][E->ien[m][i].node[kk]];
                }

                for(jj=1;jj<=vpts;jj++) {
                    temp=0.0;
                    for(kk=1;kk<=ends;kk++)   {	/* took out
						   computation of
						   depth, not
						   needed TWB */
		      TT[kk]=max(TT[kk],zero);
		      temp += min(TT[kk],one) * E->N.vpt[GNVINDEX(kk,jj)];
                    }
		    EEta[m][ (i-1)*vpts + jj ] = tempa*
		      exp( E->viscosity.E[l-1]/(temp+E->viscosity.T[l-1])
			   - E->viscosity.E[l-1]/(one +E->viscosity.T[l-1]) );
                }
            }
        break;

    case 4:

        for(m=1;m<=E->sphere.caps_per_proc;m++)
            for(i=1;i<=nel;i++)   {
                l = E->mat[m][i];
		if(E->control.mat_control) /* moved this up here TWB */
		  tempa = E->viscosity.N0[l-1] * E->VIP[m][i];
		else
		  tempa = E->viscosity.N0[l-1];

                j = 0;

                for(kk=1;kk<=ends;kk++) {
                    TT[kk] = E->T[m][E->ien[m][i].node[kk]];
                    zz[kk] = (1.-E->sx[m][3][E->ien[m][i].node[kk]]);
                }

                for(jj=1;jj<=vpts;jj++) {
                    temp=0.0;
                    zzz=0.0;
                    for(kk=1;kk<=ends;kk++)   {
                        TT[kk]=max(TT[kk],zero);
                        temp += min(TT[kk],one) * E->N.vpt[GNVINDEX(kk,jj)];
                        zzz += zz[kk] * E->N.vpt[GNVINDEX(kk,jj)];
                    }

                    /* The viscosity formulation (dimensional) is: visc=visc0*exp[(Ea+p*Va)/R*T]
                       Typical values for dry upper mantle are: Ea = 300 KJ/mol ; Va = 1.e-5 m^3/mol
                       T=T0+DT*T'; where DT - temperature contrast (from Rayleigh number)
                       T' - nondimensional temperature; T0 - surface tempereture (273 K)
                       T=DT*[(T0/DT) + T'] => visc=visc0*exp{(Ea+p*Va)/R*DT*[(T0/DT) + T']}
                       visc=visc0*exp{[(Ea/R*DT) + (p*Va/R*DT)]/[(T0/DT) + T']}
                       so: E->viscosity.E = Ea/R*DT ; E->viscosity.Z = Va/R*DT
                       p = zzz and E->viscosity.T = T0/DT */

		    EEta[m][ (i-1)*vpts + jj ] = tempa*
		      exp( (E->viscosity.E[l-1] +  E->viscosity.Z[l-1]*zzz )
			   / (E->viscosity.T[l-1]+temp) );

                }
            }
        break;


    case 5:			/* this still needs to be documented, who wrote this? */

        /* same as rheol 3, except alternative margin, VIP, formulation */
        for(m=1;m<=E->sphere.caps_per_proc;m++)
            for(i=1;i<=nel;i++)   {
                l = E->mat[m][i];
                tempa = E->viscosity.N0[l-1];
                j = 0;

                for(kk=1;kk<=ends;kk++) {
                    TT[kk] = E->T[m][E->ien[m][i].node[kk]];
                    zz[kk] = (1.-E->sx[m][3][E->ien[m][i].node[kk]]);
                }

                for(jj=1;jj<=vpts;jj++) {
                    temp=0.0;
                    zzz=0.0;
                    for(kk=1;kk<=ends;kk++)   {
                        TT[kk]=max(TT[kk],zero);
                        temp += min(TT[kk],one) * E->N.vpt[GNVINDEX(kk,jj)];
                        zzz += zz[kk] * E->N.vpt[GNVINDEX(kk,jj)];
                    }

                    if(E->control.mat_control==0)
                        EEta[m][ (i-1)*vpts + jj ] = tempa*
                            exp( E->viscosity.E[l-1]/(temp+E->viscosity.T[l-1])
                                 - E->viscosity.E[l-1]/(one +E->viscosity.T[l-1]) );

                    if(E->control.mat_control==1) {
                     /* visc1 = E->VIP[m][i];
                        visc2 = 2.0/(1./visc1 + 1.);
                        tempa_exp = tempa*
	                exp( E->viscosity.E[l-1]/(temp+E->viscosity.T[l-1])
		           - E->viscosity.E[l-1]/(one +E->viscosity.T[l-1]) );
                        visc1 = tempa*E->viscosity.max_value;
                        if(tempa_exp > visc1) tempa_exp=visc1;
                        EEta[m][ (i-1)*vpts + jj ] = visc2*tempa_exp;
                     */
                       visc1 = E->VIP[m][i];
                       visc2 = tempa*
	               exp( E->viscosity.E[l-1]/(temp+E->viscosity.T[l-1])
		          - E->viscosity.E[l-1]/(one +E->viscosity.T[l-1]) );
                       if(visc1 <= 0.95) visc2=visc1;
                       EEta[m][ (i-1)*vpts + jj ] = visc2;
                      }

                }
            }
        break;


    case 6:			/* eta = N_0 exp(E(T_0-T) + (1-z) Z_0 ) */

        for(m=1;m <= E->sphere.caps_per_proc;m++)
	  for(i=1;i <= nel;i++)   {
	    l = E->mat[m][i];
	    if(E->control.mat_control)
	      tempa = E->viscosity.N0[l-1] * E->VIP[m][i];
	    else
	      tempa = E->viscosity.N0[l-1];
	    j = 0;

	    for(kk=1;kk<=ends;kk++) {
	      TT[kk] = E->T[m][E->ien[m][i].node[kk]];
	      zz[kk] = (1.0 - E->sx[m][3][E->ien[m][i].node[kk]]);
	    }

	    for(jj=1;jj <= vpts;jj++) {
	      temp=0.0;zzz=0.0;
	      for(kk=1;kk <= ends;kk++)   {
		TT[kk]=max(TT[kk],zero);
		temp += min(TT[kk],one) * E->N.vpt[GNVINDEX(kk,jj)];
		zzz += zz[kk] * E->N.vpt[GNVINDEX(kk,jj)];
	      }
	      //fprintf(stderr,"N0 %11g T %11g T0 %11g E %11g 1-z %11g Z %11g\n",
	      //	      tempa,temp,E->viscosity.T[l-1],E->viscosity.E[l-1], zzz ,E->viscosity.Z[l-1] );
	      EEta[m][ (i-1)*vpts + jj ] = tempa*
		exp( E->viscosity.E[l-1]*(E->viscosity.T[l-1] - temp) +
		     zzz *  E->viscosity.Z[l-1] );
	    }
	  }
        break;




    }

    return;
}


void visc_from_S(E,EEta,propogate)
     struct All_variables *E;
     float **EEta;
     int propogate;
{
    float one,two,scale,stress_magnitude,depth,exponent1;
    float *eedot;

    void strain_rate_2_inv();
    int m,e,l,z,jj,kk;

    const int vpts = vpoints[E->mesh.nsd];
    const int nel = E->lmesh.nel;

    eedot = (float *) malloc((2+nel)*sizeof(float));
    one = 1.0;
    two = 2.0;

    for(m=1;m<=E->sphere.caps_per_proc;m++)  {

        /* get second invariant for all elements */
        strain_rate_2_inv(E,m,eedot,1);

        /* eedot cannot be too small, or the viscosity will go to inf */
	for(e=1;e<=nel;e++)
            eedot[e] = max(eedot[e], 1.0e-16);

        for(e=1;e<=nel;e++)   {
            exponent1= one/E->viscosity.sdepv_expt[E->mat[m][e]-1];
            scale=pow(eedot[e],exponent1-one);
            for(jj=1;jj<=vpts;jj++)
                EEta[m][(e-1)*vpts + jj] = scale*pow(EEta[m][(e-1)*vpts+jj],exponent1);
        }
    }

    free ((void *)eedot);
    return;
}

void visc_from_P(E,EEta) /* "plasticity" implementation

			 viscosity will be limited by a yield stress

			 \sigma_y  = min(a + b * (1-r), y)

			 where a,b,y are parameters input via pdepv_a,b,y

			 and

			 \eta_y = \sigma_y / (2 \eps_II)

			 where \eps_II is the second invariant. Then

			 \eta_eff = (\eta_0 \eta_y)/(\eta_0 + \eta_y)

			 for pdepv_eff = 1

			 or

			 \eta_eff = min(\eta_0,\eta_y)

			 for pdepv_eff = 0

			 where \eta_0 is the regular viscosity


			 TWB

			 */
     struct All_variables *E;
     float **EEta;
{
    float *eedot,zz[9],zzz,tau,eta_p,eta_new;
    int m,e,l,z,jj,kk;

    const int vpts = vpoints[E->mesh.nsd];
    const int nel = E->lmesh.nel;
    const int ends = enodes[E->mesh.nsd];

    void strain_rate_2_inv();

    eedot = (float *) malloc((2+nel)*sizeof(float));

    for(m=1;m<=E->sphere.caps_per_proc;m++)  {

      if(E->viscosity.pdepv_visited){

        strain_rate_2_inv(E,m,eedot,1);	/* get second invariant for all elements */

      }else{
	for(e=1;e<=nel;e++)	/* initialize with unity if no velocities around */
	  eedot[e] = 1.0e-5;
	if(m == E->sphere.caps_per_proc)
	  E->viscosity.pdepv_visited = 1;
      }

      for(e=1;e<=nel;e++)   {	/* loop through all elements */

	l = E->mat[m][e];	/* material of this element */

	for(kk=1;kk <= ends;kk++) /* nodal depths */
	  zz[kk] = (1.0 - E->sx[m][3][E->ien[m][e].node[kk]]); /* for depth, zz = 1 - r */

	for(jj=1;jj <= vpts;jj++){ /* loop through integration points */

	  zzz = 0.0;		/* get mean depth of integration point */
	  for(kk=1;kk<=ends;kk++)
	    zzz += zz[kk] * E->N.vpt[GNVINDEX(kk,jj)];

	  /* depth dependent yield stress */
	  tau = E->viscosity.pdepv_a[l] + zzz * E->viscosity.pdepv_b[l];

	  /* min of depth dep. and constant yield stress */
	  tau = min(tau,  E->viscosity.pdepv_y[l]);

	  /* yield viscosity */
	  eta_p = tau/(2.0 * eedot[e] + 1e-7) + E->viscosity.pdepv_offset;


	  if(E->viscosity.pdepv_eff){
	    /* two dashpots in series */
	    eta_new  = 1.0/(1.0/EEta[m][ (e-1)*vpts + jj ] + 1.0/eta_p);
	  }else{
	    /* min viscosities*/
	    eta_new  = min(EEta[m][ (e-1)*vpts + jj ], eta_p);
	  }
	  //fprintf(stderr,"%11g %11g %11g %11g %11g\n",eedot[e],tau,eta_p,eta_new,EEta[m][(e-1)*vpts + jj]);
	  EEta[m][(e-1)*vpts + jj] = eta_new;
        } /* end integration point loop */
      }	/* end element loop */

    } /* end caps loop */
    free ((void *)eedot);
    return;
}

/*

multiply with compositional factor which is determined by a geometric
mean average from the tracer composition, assuming two flavors and
compositions between zero and unity

*/
void visc_from_C( E, EEta)
     struct All_variables *E;
     float **EEta;
{
  float comp,comp_fac,CC[9],tcomp;
  double vmean,cc_loc;
  int m,l,z,jj,kk,i;


  const int vpts = vpoints[E->mesh.nsd];
  const int nel = E->lmesh.nel;
  const int ends = enodes[E->mesh.nsd];
  if(E->trace.nflavors != 2)
    myerror(E,"sorry, CDEPV only supports two flavors");
  if(E->composition.ncomp != 1)
    myerror(E,"CDEPV only supports one composition yet");

  for(m=1;m <= E->sphere.caps_per_proc;m++)  {
    for(i = 1; i <= nel; i++){
      /* determine composition of each of the nodes of the
	 element */
      for(kk = 1; kk <= ends; kk++){
	CC[kk] = E->composition.comp_node[m][0][E->ien[m][i].node[kk]];
	if(CC[kk] < 0)CC[kk]=0.0;
	if(CC[kk] > 1)CC[kk]=1.0;
      }
      for(jj = 1; jj <= vpts; jj++){
	/* compute mean composition  */
	cc_loc = 0.0;
	for(kk = 1; kk <= ends; kk++)
	  cc_loc += CC[kk] * E->N.vpt[GNVINDEX(kk, jj)];

	/* geometric mean of viscosity */
	vmean = exp(cc_loc  * E->viscosity.cdepv_ff[1] +
		    (1.0-cc_loc) * E->viscosity.cdepv_ff[0]);
	/* multiply the viscosity with this prefactor */
	EEta[m][ (i-1)*vpts + jj ] *= vmean;
      } /* end jj loop */
    } /* end el loop */
  } /* end cap */
}

void strain_rate_2_inv(E,m,EEDOT,SQRT)
     struct All_variables *E;
     float *EEDOT;
     int m,SQRT;
{
    void get_global_shape_fn();
    void velo_from_element();
    void construct_c3x3matrix_el();
    void get_ba_p();

    struct Shape_function GN;
    struct Shape_function_dA dOmega;
    struct Shape_function_dx GNx;

    double edot[4][4], rtf[4][9];
    double theta;
    double ba[9][9][4][7];
    float VV[4][9], Vxyz[7][9], dilation[9];

    int e, i, j, p, q, n;

    const int nel = E->lmesh.nel;
    const int dims = E->mesh.nsd;
    const int ends = enodes[dims];
    const int lev = E->mesh.levmax;
    const int ppts = ppoints[dims];
    const int sphere_key = 1;


    for(e=1; e<=nel; e++) {

        /* get shape function on presure gauss points */
        get_global_shape_fn(E, e, &GN, &GNx, &dOmega, 2,
                                sphere_key, rtf, lev, m);

        velo_from_element(E, VV, m, e, sphere_key);

        theta = rtf[1][1];


        /* Vxyz is the strain rate vector, whose relationship with
         * the strain rate tensor (e) is that:
         *    Vxyz[1] = e11
         *    Vxyz[2] = e22
         *    Vxyz[3] = e33
         *    Vxyz[4] = 2*e12
         *    Vxyz[5] = 2*e13
         *    Vxyz[6] = 2*e23
         * where 1 is theta, 2 is phi, and 3 is r
         */
        for(j=1; j<=ppts; j++) {
            Vxyz[1][j] = 0.0;
            Vxyz[2][j] = 0.0;
            Vxyz[3][j] = 0.0;
            Vxyz[4][j] = 0.0;
            Vxyz[5][j] = 0.0;
            Vxyz[6][j] = 0.0;
            dilation[j] = 0.0;
        }

        if ((theta < 0.09) || (theta > 3.05)) {
            /* When the element is close to the poles, use a more
             * precise method to compute the strain rate. */

            if ((e-1)%E->lmesh.elz==0) {
                construct_c3x3matrix_el(E,e,&E->element_Cc,&E->element_Ccx,lev,m,1);
            }

            get_ba_p(&(E->N), &GNx, &E->element_Cc, &E->element_Ccx,
                     rtf, E->mesh.nsd, ba);

            for(j=1;j<=ppts;j++)
                for(p=1;p<=6;p++)
                    for(i=1;i<=ends;i++)
                        for(q=1;q<=dims;q++) {
                            Vxyz[p][j] += ba[i][j][q][p] * VV[q][i];
                        }

        }
        else {
            for(j=1; j<=ppts; j++) {
                for(i=1; i<=ends; i++) {
                    Vxyz[1][j] += (VV[1][i] * GNx.ppt[GNPXINDEX(0, i, j)]
                                   + VV[3][i] * E->N.ppt[GNPINDEX(i, j)])
                        * rtf[3][j];
                    Vxyz[2][j] += ((VV[2][i] * GNx.ppt[GNPXINDEX(1, i, j)]
                                    + VV[1][i] * E->N.ppt[GNPINDEX(i, j)]
                                    * cos(rtf[1][j])) / sin(rtf[1][j])
                                   + VV[3][i] * E->N.ppt[GNPINDEX(i, j)])
                        * rtf[3][j];
                    Vxyz[3][j] += VV[3][i] * GNx.ppt[GNPXINDEX(2, i, j)];

                    Vxyz[4][j] += ((VV[1][i] * GNx.ppt[GNPXINDEX(1, i, j)]
                                    - VV[2][i] * E->N.ppt[GNPINDEX(i, j)]
                                    * cos(rtf[1][j])) / sin(rtf[1][j])
                                   + VV[2][i] * GNx.ppt[GNPXINDEX(0, i, j)])
                        * rtf[3][j];
                    Vxyz[5][j] += VV[1][i] * GNx.ppt[GNPXINDEX(2, i, j)]
                        + rtf[3][j] * (VV[3][i] * GNx.ppt[GNPXINDEX(0, i, j)]
                                       - VV[1][i] * E->N.ppt[GNPINDEX(i, j)]);
                    Vxyz[6][j] += VV[2][i] * GNx.ppt[GNPXINDEX(2, i, j)]
                        + rtf[3][j] * (VV[3][i]
                                       * GNx.ppt[GNPXINDEX(1, i, j)]
                                       / sin(rtf[1][j])
                                       - VV[2][i] * E->N.ppt[GNPINDEX(i, j)]);
                }
            }
        } /* end of else */

        if(E->control.inv_gruneisen != 0) {
            for(j=1; j<=ppts; j++)
                dilation[j] = (Vxyz[1][j] + Vxyz[2][j] + Vxyz[3][j]) / 3.0;
        }

        edot[1][1] = edot[2][2] = edot[3][3] = 0;
        edot[1][2] = edot[1][3] = edot[2][3] = 0;

        /* edot is 2 * (the deviatoric strain rate tensor) */
        for(j=1; j<=ppts; j++) {
            edot[1][1] += 2.0 * (Vxyz[1][j] - dilation[j]);
            edot[2][2] += 2.0 * (Vxyz[2][j] - dilation[j]);
            edot[3][3] += 2.0 * (Vxyz[3][j] - dilation[j]);
            edot[1][2] += Vxyz[4][j];
            edot[1][3] += Vxyz[5][j];
            edot[2][3] += Vxyz[6][j];
        }

        EEDOT[e] = edot[1][1] * edot[1][1]
            + edot[1][2] * edot[1][2] * 2.0
            + edot[2][2] * edot[2][2]
            + edot[2][3] * edot[2][3] * 2.0
            + edot[3][3] * edot[3][3]
            + edot[1][3] * edot[1][3] * 2.0;
    }

    if(SQRT)
	for(e=1;e<=nel;e++)
	    EEDOT[e] =  sqrt(0.5 *EEDOT[e]);
    else
	for(e=1;e<=nel;e++)
	    EEDOT[e] *=  0.5;

    return;
}


static void apply_low_visc_wedge_channel(struct All_variables *E, float **evisc)
{
    void parallel_process_termination();

    int i,j,m;
    const int vpts = vpoints[E->mesh.nsd];
    float *F;

    /* low viscosity channel/wedge require tracers to work */
    if(E->control.tracer == 0) {
        if(E->parallel.me == 0) {
            fprintf(stderr, "Error: low viscosity channel/wedge is turned on, "
                   "but tracer is off!\n");
            fprintf(E->fp, "Error: low viscosity channel/wedge is turned on, "
                   "but tracer is off!\n");
            fflush(E->fp);
        }
        parallel_process_termination();
    }


    F = (float *)malloc((E->lmesh.nel+1)*sizeof(float));
    for(i=1 ; i<=E->lmesh.nel ; i++)
        F[i] = 0.0;

    /* if low viscosity channel ... */
    if(E->viscosity.channel)
        low_viscosity_channel_factor(E, F);


    /* if low viscosity wedge ... */
    if(E->viscosity.wedge)
        low_viscosity_wedge_factor(E, F);


    for(i=1 ; i<=E->lmesh.nel ; i++) {
        if (F[i] != 0.0)
            for(m = 1 ; m <= E->sphere.caps_per_proc ; m++) {
                for(j=1;j<=vpts;j++) {
                    evisc[m][(i-1)*vpts + j] = F[i];
            }
        }
    }


    free(F);

    return;
}




static void low_viscosity_channel_factor(struct All_variables *E, float *F)
{
    int i, ii, k, m, e, ee;
    int nz_min[NCS], nz_max[NCS];
    const int flavor = 0;
    double rad_mean, rr;

    for(m=1; m<=E->sphere.caps_per_proc; m++) {
        /* find index of radius corresponding to lv_min_radius */
        for(e=1; e<=E->lmesh.elz; e++) {
            rad_mean = 0.5 * (E->sx[m][3][E->ien[m][e].node[1]] +
                              E->sx[m][3][E->ien[m][e].node[8]]);
            if(rad_mean >= E->viscosity.lv_min_radius) break;
        }
        nz_min[m] = e;

        /* find index of radius corresponding to lv_max_radius */
        for(e=E->lmesh.elz; e>=1; e--) {
            rad_mean = 0.5 * (E->sx[m][3][E->ien[m][e].node[1]] +
                              E->sx[m][3][E->ien[m][e].node[8]]);
            if(rad_mean <= E->viscosity.lv_max_radius) break;
        }
        nz_max[m] = e;
    }



    for(m=1; m<=E->sphere.caps_per_proc; m++) {
        for(k=1; k<=E->lmesh.elx*E->lmesh.ely; k++) {
            for(i=nz_min[m]; i<=nz_max[m]; i++) {
                e = (k-1)*E->lmesh.elz + i;

                rad_mean = 0.5 * (E->sx[m][3][E->ien[m][e].node[1]] +
                                  E->sx[m][3][E->ien[m][e].node[8]]);

                /* loop over elements below e */
                for(ii=i; ii>=nz_min[m]; ii--) {
                    ee = (k-1)*E->lmesh.elz + ii;

                    rr = 0.5 * (E->sx[m][3][E->ien[m][ee].node[1]] +
                                E->sx[m][3][E->ien[m][ee].node[8]]);

                    /* if ee has tracers in it and is within the channel */
                    if((E->trace.ntracer_flavor[m][flavor][ee] > 0) &&
                       (rad_mean <= rr + E->viscosity.lv_channel_thickness)) {
                           F[e] = E->viscosity.lv_reduction;
                           break;
                       }
                }
            }
        }
    }


    /** debug **
    for(m=1; m<=E->sphere.caps_per_proc; m++)
        for(e=1; e<=E->lmesh.nel; e++)
            fprintf(stderr, "lv_reduction: %d %e\n", e, F[e]);
    /**/

    return;
}


static void low_viscosity_wedge_factor(struct All_variables *E, float *F)
{
    int i, ii, k, m, e, ee;
    int nz_min[NCS], nz_max[NCS];
    const int flavor = 0;
    double rad_mean, rr;

    for(m=1; m<=E->sphere.caps_per_proc; m++) {
        /* find index of radius corresponding to lv_min_radius */
        for(e=1; e<=E->lmesh.elz; e++) {
            rad_mean = 0.5 * (E->sx[m][3][E->ien[m][e].node[1]] +
                              E->sx[m][3][E->ien[m][e].node[8]]);
            if(rad_mean >= E->viscosity.lv_min_radius) break;
        }
        nz_min[m] = e;

        /* find index of radius corresponding to lv_max_radius */
        for(e=E->lmesh.elz; e>=1; e--) {
            rad_mean = 0.5 * (E->sx[m][3][E->ien[m][e].node[1]] +
                              E->sx[m][3][E->ien[m][e].node[8]]);
            if(rad_mean <= E->viscosity.lv_max_radius) break;
        }
        nz_max[m] = e;
    }



    for(m=1; m<=E->sphere.caps_per_proc; m++) {
        for(k=1; k<=E->lmesh.elx*E->lmesh.ely; k++) {
            for(i=nz_min[m]; i<=nz_max[m]; i++) {
                e = (k-1)*E->lmesh.elz + i;

                rad_mean = 0.5 * (E->sx[m][3][E->ien[m][e].node[1]] +
                                  E->sx[m][3][E->ien[m][e].node[8]]);

                /* loop over elements below e */
                for(ii=i; ii>=nz_min[m]; ii--) {
                    ee = (k-1)*E->lmesh.elz + ii;

                    /* if ee has tracers in it */
                    if(E->trace.ntracer_flavor[m][flavor][ee] > 0) {
                        F[e] = E->viscosity.lv_reduction;
                        break;
                    }
                }
            }
        }
    }


    /** debug **
    for(m=1; m<=E->sphere.caps_per_proc; m++)
        for(e=1; e<=E->lmesh.nel; e++)
            fprintf(stderr, "lv_reduction: %d %e\n", e, F[e]);
    /**/

    return;
}