ion_trim.cpp

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/* This file is part of Cloudy and is copyright (C)1978-2017 by Gary J. Ferland and
 * others.  For conditions of distribution and use see copyright notice in license.txt */
/*ion_trim raise or lower most extreme stages of ionization considered,
 * called by ConvBase - ion limits were originally set by  */
#include "cddefines.h"
#include "ion_trim.h"

#include "heavy.h"
#include "conv.h"
#include "rfield.h"
#include "phycon.h"
#include "mole.h"
#include "thermal.h"
#include "iso.h"
#include "struc.h"
#include "ionbal.h"
#include "dense.h"

void ion_trim_untrim( long nelem )
{
        DEBUG_ENTRY( "ion_trim_untrim()" );
        dense.IonLow[nelem] = 0;
        dense.IonHigh[nelem] = nelem+1;
}
void ion_trim_invalidate( long nelem )
{
        DEBUG_ENTRY( "ion_trim_invalidate()" );
        dense.IonLow[nelem] = -1;
        dense.IonHigh[nelem] = -1;
}

STATIC void ion_trim_from_set( long nelem);

void ion_trim_init()
{
        DEBUG_ENTRY( "ion_trim_init()" );
        for(long nelem=ipHYDROGEN; nelem < LIMELM; nelem++ )
        {
                if( !dense.lgElmtOn[nelem] )
                {
                        ion_trim_invalidate(nelem);
                        continue;
                }
                
                if( dense.lgSetIoniz[nelem] )
                {
                        /* >>chng 04 jan 13, add this test, caught by Orly Gnat */
                        /* check on actual zero abundances of lower stages - this will only 
                         * happen when ionization is set with element ionization command */
                        ion_trim_from_set(nelem);
                }
                else
                {
                        // IonHigh[n] is the highest stage of ionization present
                        // the IonHigh array index is on the C scale, so [0] is hydrogen
                        // the value is also on the C scale, so element [nelem] can range
                        // from 0 to nelem+1 
                        dense.IonHigh[nelem] = nelem + 1;
                        
                        dense.IonLow[nelem] = 0;
                        // for very intense radiation fields very heavy elements, N>Fe, will fail
                        // in ion_solver due to ill conditioned matrix.  all populations are in
                        // fully stripped state.  Start will fully stripped ion distribution in this case.
                        if( rfield.uh > 1e15 )
                        {
                                //trim down highest stage to be within incident radiation field
                                while ( ionbal.lgTrimhiOn &&
                                                  rfield.anu(Heavy.ipHeavy[nelem][dense.IonHigh[nelem]-1]) > 
                                                  rfield.anu(rfield.nflux) && dense.IonHigh[nelem]>1 ) 
                                        --dense.IonHigh[nelem];
                                
                                if (ionbal.lgTrimloOn)
                                        dense.IonLow[nelem] = max( 0 , dense.IonHigh[nelem]-1 );
                        }
                }                               
                
                // make low-stage populations zero
                for( long ion=0; ion<dense.IonLow[nelem]; ++ion )
                {
                        dense.xIonDense[nelem][dense.IonLow[nelem]] += dense.xIonDense[nelem][ion];
                        dense.xIonDense[nelem][ion] = 0.;
                }
                for( long ion=nelem+1; ion>dense.IonHigh[nelem]; --ion )
                {
                        dense.xIonDense[nelem][dense.IonHigh[nelem]] += dense.xIonDense[nelem][ion];
                        dense.xIonDense[nelem][ion] = 0.;
                }
        }
}

void ion_trim_from_set()
{
        DEBUG_ENTRY( "ion_trim_from_set()" );
        for( long nelem=ipHYDROGEN; nelem < LIMELM; nelem++ )
        {
                if( dense.lgSetIoniz[nelem] )
                {
                        ion_trim_from_set(nelem);
                }                         
        }
}

STATIC void ion_trim_from_set( long nelem )
{
        DEBUG_ENTRY( "ion_trim_from_set()" );
        dense.IonLow[nelem] = 0;
        dense.IonHigh[nelem] = nelem + 1;
        while( ionbal.lgTrimloOn && dense.SetIoniz[nelem][dense.IonLow[nelem]] < dense.density_low_limit )
                ++dense.IonLow[nelem];
        while( ionbal.lgTrimhiOn && dense.SetIoniz[nelem][dense.IonHigh[nelem]] < dense.density_low_limit )
                --dense.IonHigh[nelem];
}

void ion_trim_small (long nelem, double abund_total)
{
        DEBUG_ENTRY( "ion_trim_small()" );
        while( ionbal.lgTrimhiOn && dense.IonHigh[nelem] > dense.IonLow[nelem] && 
                dense.xIonDense[nelem][dense.IonHigh[nelem]] < 1e-25*abund_total &&
                dense.IonHigh[nelem] > 1)
        {
                ASSERT( dense.xIonDense[nelem][dense.IonHigh[nelem]] >= 0. );
                /* zero out abundance and heating due to stage of ionization we are about to zero out */
                dense.xIonDense[nelem][dense.IonHigh[nelem]] = 0.;
                thermal.setHeating(nelem,dense.IonHigh[nelem]-1,0.);
                /* decrement counter */
                --dense.IonHigh[nelem];
        }
}

void mole_ion_trim(void)
{
        DEBUG_ENTRY( "mole_ion_trim()" );
        for (ChemNuclideList::iterator atom = nuclide_list.begin();
                  atom != nuclide_list.end(); ++atom)
        {
                if( !(*atom)->lgHasLinkedIon())
                        continue;
                const long int nelem=(*atom)->el->Z-1;
                if( !dense.lgElmtOn[nelem] )
                        continue;

                for (long int ion=0;ion<nelem+2;ion++) 
                {
                        if ((*atom)->ipMl[ion] != -1)
                        {
                                if ( ionbal.lgTrimloOn && dense.IonLow[nelem] > ion )
                                {
                                        if( dense.xIonDense[nelem][ion] > ( ionbal.trimlo * dense.gas_phase[nelem] ) )
                                        {
                                                dense.IonLow[nelem] = ion;
                                        }
                                        else
                                        {
                                                dense.xIonDense[nelem][dense.IonLow[nelem]] += dense.xIonDense[nelem][ion];
                                                dense.xIonDense[nelem][ion] = 0.;
                                        }
                                }

                                if ( ionbal.lgTrimhiOn && dense.IonHigh[nelem] < ion )
                                {
                                        if( dense.xIonDense[nelem][ion] > ( ionbal.trimhi * dense.gas_phase[nelem] ) )
                                        {
                                                dense.IonHigh[nelem] = ion;
                                        }
                                        else
                                        {
                                                dense.xIonDense[nelem][dense.IonHigh[nelem]] += dense.xIonDense[nelem][ion];
                                                dense.xIonDense[nelem][ion] = 0.;
                                        }
                                }
                        }
                }
        }
}

void ion_trim(
        /* nelem is on the C scale, 0 for H, 5 for C */
        long int nelem )
{

        /* this will remember that higher stages trimed up or down */
        bool lgHi_Down = false;
        bool lgHi_Up = false;
        bool lgHi_Up_enable;
        /* this will remember that lower stages trimmed up or own*/
        bool lgLo_Up = false;
        bool lgLo_Down = false;
        long int ion_lo_save = dense.IonLow[nelem],
                ion_hi_save = dense.IonHigh[nelem];
        long int ion;
        realnum trimhi , trimlo;

        /* this is debugging code that turns on print after certain number of calls */
        /*realnum xlimit = SMALLFLOAT *10.;*/
        /*static int ncall=0;
        if( nelem==5 )
                ++ncall;*/

        DEBUG_ENTRY( "ion_trim()" );

        /* this routine should not be called early in the simulation, before
         * things have settled down */
        ASSERT( conv.nTotalIoniz>2 );

        /*confirm all ionization stages are within their range of validity */
        ASSERT( nelem >= ipHELIUM && nelem < LIMELM );
        ASSERT( dense.IonLow[nelem] >= 0 );
        ASSERT( dense.IonHigh[nelem] <= nelem+1 );
        /* IonHigh can be equal to IonLow */
        ASSERT( dense.IonLow[nelem] <= dense.IonHigh[nelem] );

        /* during search phase of mostly neutral matter the electron density
         * can be vastly too large, and the ionization suppressed as a result.
         * during search do not trim down or up as much */
        if( conv.lgSearch )
        {
                trimhi = (realnum)ionbal.trimhi * 1e-4f;
                trimlo = (realnum)ionbal.trimlo * 1e-4f;
        }
        else
        {
                trimhi = (realnum)ionbal.trimhi;
                trimlo = (realnum)ionbal.trimlo;
        }

        /* helium is special case since abundance is so high, and He+ CT with 
         * CO is the dominant CO destruction process in molecular regions */
        if( nelem == ipHELIUM )
        {
                /* never want to trip up a lower stage of ionization */
                trimlo = SMALLFLOAT;

                /* if He+ is highest stage of ionization, probably want to keep it
                 * since important for CO chemistry in molecular clouds */
                if( dense.IonHigh[ipHELIUM] == 1 )
                {
                        trimhi = MIN2( trimhi , 1e-20f );
                }
                else if( dense.IonHigh[ipHELIUM] == 2 )
                {
                        if( conv.lgSearch )
                        {
                                /* during search phase we may be quite far from solution, in the
                                 * case of a PDR sim the electron density may be vastly higher 
                                 * than it will be with stable solution.  He++ can be very important
                                 * for the chemistry and we want to consider it.  Make the
                                 * threshold for ignoring He++ much higher than normal to prevent
                                 * a premature removal of the ion */
                                trimhi = MIN2( trimhi , 1e-17f ); 
                        }
                        else
                        {
                                /* similar smaller upper limit for ion*/
                                trimhi = MIN2( trimhi , 1e-12f ); 
                        }
                }
        }

        /* logic for PDRs, for elements included in chemistry, need stable solutions, 
         * keep 3 ion stages in most cases - added by NA to do HII/PDR sims */
        if( !mole_global.lgNoMole )
        {
                trimlo = SMALLFLOAT;
                if(dense.IonHigh[nelem] ==2)
                {
                        trimhi = MIN2(trimhi, 1e-20f);
                }
        }

        /* raise or lower highest and lowest stages of ionization to
         * consider only significant stages
         * IonHigh[nelem]  stage of ionization  */

        /* this is a special block for initialization only - it checks on absurd abundances
         * and can trim multiple stages of ionization at one time. */
        if( conv.lgSearch )
        {
                /* special - trim down higher stages if they have essentially zero abundance */
                while( ionbal.lgTrimhiOn && 
                        (dense.xIonDense[nelem][dense.IonHigh[nelem]]/dense.gas_phase[nelem] < dense.density_low_limit || 
                        dense.xIonDense[nelem][dense.IonHigh[nelem]] < dense.density_low_limit ) && 
                        /* >>chng 02 may 12, rm +1 since this had effect of not allowing fully atomic */
                        dense.IonHigh[nelem] > dense.IonLow[nelem] )
                {
                        /* dense.xIonDense[nelem][i] is density of i+1 th ionization stage (cm^-3)
                         * the -1 is correct for the heating, -1 since heating is caused by ionization of stage below it */
                        dense.xIonDense[nelem][dense.IonHigh[nelem]-1] +=
                                dense.xIonDense[nelem][dense.IonHigh[nelem]];
                        dense.xIonDense[nelem][dense.IonHigh[nelem]] = 0.;
                        thermal.setHeating(nelem,dense.IonHigh[nelem]-1,0.);
                        if( dense.IonHigh[nelem] == nelem+1-NISO )
                        {
                                long int ipISO = nelem - dense.IonHigh[nelem];
                                ASSERT( ipISO>=0 && ipISO<NISO );
                                for( long level = 0; level < iso_sp[ipISO][nelem].numLevels_max; level++ )
                                        iso_sp[ipISO][nelem].st[level].Pop() = 0.;
                        }

                        /* decrement high stage limit */
                        --dense.IonHigh[nelem];
                        ASSERT( dense.IonHigh[nelem] >= 0);
                        /* remember this happened */
                        lgHi_Down = true;
                }

                /* special - trim up lower stages trim if they have essentially zero abundance */
                while( ionbal.lgTrimloOn && 
                        (dense.xIonDense[nelem][dense.IonLow[nelem]]/dense.gas_phase[nelem] < dense.density_low_limit || 
                        dense.xIonDense[nelem][dense.IonLow[nelem]] < dense.density_low_limit ) && 
                        dense.IonLow[nelem] < dense.IonHigh[nelem] - 1 )
                {
                        /* dense.xIonDense[nelem][i] is density of ith ionization stage (cm^-3)
                         * there is no-1 since we are removing the agent that heats */
                        dense.xIonDense[nelem][dense.IonLow[nelem]+1] += 
                                dense.xIonDense[nelem][dense.IonLow[nelem]];
                        dense.xIonDense[nelem][dense.IonLow[nelem]] = 0.;
                        /* >>chng 01 aug 04, remove -1 which clobbers thermal.heating when IonLow == 0 */
                        thermal.setHeating(nelem,dense.IonLow[nelem],0.);
                        if( dense.IonLow[nelem] == nelem+1-NISO )
                        {
                                long int ipISO = nelem - dense.IonLow[nelem];
                                ASSERT( ipISO>=0 && ipISO<NISO );
                                for( long level = 0; level < iso_sp[ipISO][nelem].numLevels_max; level++ )
                                        iso_sp[ipISO][nelem].st[level].Pop() = 0.;
                        }

                        /* increment low stage limit */
                        ++dense.IonLow[nelem];
                        lgLo_Up = true;
                }
        }

        /* sanity check */
        ASSERT( dense.IonLow[nelem] <= dense.IonHigh[nelem] );

        /* this checks on error condition where the gas is stupendously highly ionized,
         * the low limit is already one less than high, and we need to raise the low
         * limit further */
        if( dense.IonHigh[nelem] > 1 &&
                (dense.IonLow[nelem]==dense.IonHigh[nelem]-1) &&
                (dense.xIonDense[nelem][dense.IonLow[nelem]] < dense.density_low_limit) )
        {
#               if 0
                fprintf(ioQQQ,
                        "PROBLEM DISASTER the density of ion %li of element %s is too small to be computed on this cpu.\n",
                        dense.IonLow[nelem]+1,
                        elementnames.chElementName[nelem]);
                fprintf(ioQQQ,
                        "Turn off the element with the command ELEMENT XXX OFF or do not consider "
                        "gas with low density, the current hydrogen density is %.2e cm-3.\n",
                        dense.gas_phase[ipHYDROGEN]);
                fprintf(ioQQQ,
                        "The outer radius of the cloud is %.2e cm - should a stopping "
                        "radius be set?\n",
                        radius.Radius );
                fprintf(ioQQQ,
                        "The abort flag is being set - the calculation is stopping.\n");
#               endif
                //lgAbort = true;
                dense.xIonDense[nelem][dense.IonLow[nelem]] = (realnum)dense.density_low_limit;
                return;
        }

        /* trim down high stages that have too small an abundance */
        while( ionbal.lgTrimhiOn && 
                dense.IonHigh[nelem] > dense.IonLow[nelem]  && 
                ( (dense.xIonDense[nelem][dense.IonHigh[nelem]]/dense.gas_phase[nelem] <= 
                trimhi ) ||
                (dense.xIonDense[nelem][dense.IonHigh[nelem]] <= dense.density_low_limit ) )
                ) 
        {
                /* >>chng 03 sep 30, the atom and its first ion are a special case
                 * since we want to compute even trivial ions in molecular clouds */
                if( dense.IonHigh[nelem]>1 ||
                        (dense.IonHigh[nelem]==1&&dense.xIonDense[nelem][1]<100.*dense.density_low_limit) )
                {
                        dense.xIonDense[nelem][dense.IonHigh[nelem]-1] += 
                                dense.xIonDense[nelem][dense.IonHigh[nelem]];
                        dense.xIonDense[nelem][dense.IonHigh[nelem]] = 0.;
                        thermal.setHeating(nelem,dense.IonHigh[nelem]-1,0.);
                        if( dense.IonHigh[nelem] == nelem+1-NISO )
                        {
                                long int ipISO = nelem - dense.IonHigh[nelem];
                                ASSERT( ipISO>=0 && ipISO<NISO );
                                for( long level = 0; level < iso_sp[ipISO][nelem].numLevels_max; level++ )
                                        iso_sp[ipISO][nelem].st[level].Pop() = 0.;
                        }
                        --dense.IonHigh[nelem];
                        lgHi_Down = true;
                }
                else
                {
                        break;
                }
        }

        /* trim up highest stages - will this be done? */
        lgHi_Up_enable = true;
        /* trimming can be turned off */
        if( !ionbal.lgTrimhiOn )
                lgHi_Up_enable = false;
        /* high stage is already fully stripped */
        if( dense.IonHigh[nelem]>=nelem+1 )
                lgHi_Up_enable = false;
        /* we have previously trimmed this stage down */
        if( lgHi_Down )
                lgHi_Up_enable = false;
        /* we are in neutral gas */
        if( dense.xIonDense[ipHYDROGEN][1]/dense.gas_phase[ipHYDROGEN]<0.9  )
                lgHi_Up_enable = false;

        if( lgHi_Up_enable )
        {
                realnum abundold = 0;
                if( nzone>2 ) 
                        abundold = struc.xIonDense[nzone-3][nelem][dense.IonHigh[nelem]]/
                        SDIV( struc.gas_phase[nzone-3][nelem]);
                realnum abundnew = dense.xIonDense[nelem][dense.IonHigh[nelem]]/dense.gas_phase[nelem];
                /* only raise highest stage if ionization potential of next highest stage is within
                 * continuum array and the abundance of the highest stage is significant */
                if( (Heavy.Valence_IP_Ryd[nelem][dense.IonHigh[nelem]] < rfield.anu(rfield.nflux-1) ||
                        Heavy.Valence_IP_Ryd[nelem][dense.IonHigh[nelem]] < phycon.te_ryd*10.) &&
                        dense.xIonDense[nelem][dense.IonHigh[nelem]]/dense.gas_phase[nelem] > trimhi &&
                        /* this checks that abundance of highest stage is increasing */
                        abundnew > abundold*1.01 )
                {
                        /*fprintf(ioQQQ,"uuppp %li %li \n", nelem, dense.IonHigh[nelem] );*/
                        /* raise highest level of ionization */
                        ++dense.IonHigh[nelem];
                        lgHi_Up = true;
                        /* set abundance to almost zero so that sanity check elsewhere will be ok */
                        dense.xIonDense[nelem][dense.IonHigh[nelem]] = (dense.density_low_limit*10.);
                        dense.xIonDense[nelem][dense.IonHigh[nelem]-1] -= 
                                dense.xIonDense[nelem][dense.IonHigh[nelem]];
                        long int ipISO = nelem - dense.IonHigh[nelem];
                        if (ipISO >= 0 && ipISO < NISO)
                                iso_sp[ipISO][nelem].st[0].Pop() = dense.xIonDense[nelem][dense.IonHigh[nelem]];
                }
        }

        /* sanity check */
        ASSERT( dense.IonLow[nelem] <= dense.IonHigh[nelem] );

        /* lower lowest stage of ionization if we have significant abundance at current lowest */
        if( dense.xIonDense[nelem][dense.IonLow[nelem]]/dense.gas_phase[nelem] > trimlo &&
                dense.IonLow[nelem] > 0 )
        {
                /* lower lowest level of ionization */
                --dense.IonLow[nelem];
                lgLo_Down = true;
                /* >>chng 01 aug 02, set this to zero so that sanity check elsewhere will be ok */
                dense.xIonDense[nelem][dense.IonLow[nelem]] = (realnum)dense.density_low_limit;
                dense.xIonDense[nelem][dense.IonLow[nelem]+1] -= 
                        dense.xIonDense[nelem][dense.IonLow[nelem]];
                long int ipISO = nelem - dense.IonLow[nelem];
                if (ipISO >= 0 && ipISO < NISO)
                        iso_sp[ipISO][nelem].st[0].Pop() = dense.xIonDense[nelem][dense.IonLow[nelem]];
        }

        /* raise lowest stage of ionization, but only if we are near illuminated face of cloud*/
        else if( ionbal.lgTrimloOn && nzone < 10 &&
                (dense.xIonDense[nelem][dense.IonLow[nelem]]/dense.gas_phase[nelem] <= (realnum)trimlo) && 
                (dense.IonLow[nelem] < (dense.IonHigh[nelem] - 2) ) )
        {
                /* raise lowest level of ionization */
                dense.xIonDense[nelem][dense.IonLow[nelem]+1] += 
                        dense.xIonDense[nelem][dense.IonLow[nelem]];
                dense.xIonDense[nelem][dense.IonLow[nelem]] = 0.;
                /* no minus one in below since this is low bound, already bounds at atom */
                thermal.setHeating(nelem,dense.IonLow[nelem],0.);
                if( dense.IonLow[nelem] == nelem+1-NISO )
                {
                        long int ipISO = nelem - dense.IonLow[nelem];
                        ASSERT( ipISO>=0 && ipISO<NISO );
                        for( long level = 0; level < iso_sp[ipISO][nelem].numLevels_max; level++ )
                                iso_sp[ipISO][nelem].st[level].Pop() = 0.;
                }
                ++dense.IonLow[nelem];
                lgLo_Up = true;
        }
        /* test on zero */
        else if( ionbal.lgTrimloOn && (dense.xIonDense[nelem][dense.IonLow[nelem]] < dense.density_low_limit) && 
                /*>>chng 06 may 24, from IonLow < IonHigh to <IonHigh-1 because
                 * old test would allow low to be raised too high, which then
                 * leads to insanity */
                (dense.IonLow[nelem] < dense.IonHigh[nelem]-1) )
        {
                while(dense.xIonDense[nelem][dense.IonLow[nelem]] < dense.density_low_limit && 
                        /* >>chng 07 feb 27 from < IonHigh to < IonHigh-1 to prevent raising
                         * low to high */
                        (dense.IonLow[nelem] < dense.IonHigh[nelem]-1) )
                {
                        /* raise lowest level of ionization */
                        dense.xIonDense[nelem][dense.IonLow[nelem]+1] += 
                                dense.xIonDense[nelem][dense.IonLow[nelem]];
                        dense.xIonDense[nelem][dense.IonLow[nelem]] = 0.;
                        /* no minus one in below since this is low bound, already bounds at atom */
                        thermal.setHeating(nelem,dense.IonLow[nelem],0.);
                        if( dense.IonLow[nelem] == nelem+1-NISO )
                        {
                                long int ipISO = nelem - dense.IonLow[nelem];
                                ASSERT( ipISO>=0 && ipISO<NISO );
                                for( long level = 0; level < iso_sp[ipISO][nelem].numLevels_max; level++ )
                                        iso_sp[ipISO][nelem].st[level].Pop() = 0.;
                        }
                        ++dense.IonLow[nelem];
                        lgLo_Up = true;
                }
        }

        /* sanity check */
        ASSERT( dense.IonLow[nelem] <= dense.IonHigh[nelem] );

        /* these are standard bounds checks that appear throughout this routine
         * dense.xIonDense[IonLow] is first one with positive abundances
         * 
         * in case where lower ionization stage was just lowered the abundance
         * was set to dense.density_low_limit so test must be < dense.density_low_limit */
        ASSERT( dense.IonLow[nelem] <= 1 ||
                dense.xIonDense[nelem][dense.IonLow[nelem]-1] == 0. );

        ASSERT( (dense.IonLow[nelem]==0 && dense.IonHigh[nelem]==0 ) || lgLo_Up ||
                          ! ionbal.lgTrimloOn ||
                          dense.xIonDense[nelem][dense.IonLow[nelem]] >= dense.density_low_limit ||
                          dense.xIonDense[nelem][dense.IonLow[nelem]]/dense.gas_phase[nelem] >= dense.density_low_limit ||
                          /*>>chng 06 may 24, include this to cover case where cap is set by not allowing
                                * lower limit to come up to upper limit */
                          (dense.IonLow[nelem]==dense.IonHigh[nelem]-1 ));

        {
                /* option to print out what has happened so far .... */
                enum {DEBUG_LOC=false};
                if( DEBUG_LOC && nelem == ipHELIUM )
                {
                        if( lgHi_Down ||lgHi_Up ||lgLo_Up ||lgLo_Down )
                        {
                                fprintf(ioQQQ,"DEBUG TrimZone\t%li\t",nzone );
                                if(  lgHi_Down )
                                {
                                        fprintf(ioQQQ,"high dn %li to %li",
                                                ion_hi_save , 
                                                dense.IonHigh[nelem] );
                                }
                                if( lgHi_Up )
                                {
                                        fprintf(ioQQQ,"high up %li to %li",
                                                ion_hi_save , 
                                                dense.IonHigh[nelem] );
                                }
                                if( lgLo_Up )
                                {
                                        fprintf(ioQQQ,"low up %li to %li",
                                                ion_lo_save , 
                                                dense.IonLow[nelem] );
                                }
                                if( lgLo_Down )
                                {
                                        fprintf(ioQQQ,"low dn %li to %li",
                                                ion_lo_save , 
                                                dense.IonLow[nelem] );
                                }
                                fprintf(ioQQQ,"\n" );
                        }
                }
        }

        /* option to print if any trimming occurred */
        if( lgHi_Down || lgHi_Up || lgLo_Up || lgLo_Down )
        {
                conv.lgIonStageTrimed = true;
                {
                        /* option to print out what has happened so far .... */
                        enum {DEBUG_LOC=false};
                        if( DEBUG_LOC && nelem==ipHELIUM )
                        {
                                fprintf(ioQQQ,"DEBUG ion_trim zone\t%.2f \t%li\t", fnzone, nelem);
                                if( lgHi_Down  )
                                        fprintf(ioQQQ,"\tHi_Down");
                                if( lgHi_Up )
                                        fprintf(ioQQQ,"\tHi_Up");
                                if( lgLo_Up )
                                        fprintf(ioQQQ,"\tLo_Up");
                                if( lgLo_Down )
                                        fprintf(ioQQQ,"\tLo_Down");
                                fprintf(ioQQQ,"\n");
                        }
                }
        }

        /* asserts that that densities of ion stages that are now turned 
         * off are zero */
        for( ion=0; ion<dense.IonLow[nelem]; ++ion )
        {
                ASSERT( dense.xIonDense[nelem][ion] == 0. );
        }
        for( ion=dense.IonHigh[nelem]+1; ion<nelem+1; ++ion )
        {
                ASSERT( dense.xIonDense[nelem][ion] == 0. );
        }

        for( ion=dense.IonLow[nelem]; ion<=dense.IonHigh[nelem]; ++ion )
        {
                /* in case where ionization stage was changed the
                 * density is zero, we set it to SMALLFLOAT since a density
                 * of zero is not possible */
                dense.xIonDense[nelem][ion] = MAX2(dense.xIonDense[nelem][ion], SMALLFLOAT);
        }
        return;
}

// Try winnowing down ion_trim
void ion_trim2(
        /* nelem is on the C scale, 0 for H, 5 for C */
        long int nelem )
{

        /* this will remember that higher stages trimed up or down */
        bool lgHi_Down = false;
        /* this will remember that lower stages trimmed up or own*/
        bool lgLo_Up = false;
        long int ion_lo_save = dense.IonLow[nelem],
                ion_hi_save = dense.IonHigh[nelem];
        long int ion;
        realnum trimhi , trimlo, trimcharge;

        /* this is debugging code that turns on print after certain number of calls */
        /*realnum xlimit = SMALLFLOAT *10.;*/
        /*static int ncall=0;
        if( nelem==5 )
                ++ncall;*/

        DEBUG_ENTRY( "ion_trim2()" );

        /*confirm all ionization stages are within their range of validity */
        ASSERT( nelem >= ipHYDROGEN && nelem < LIMELM );
        ASSERT( dense.IonLow[nelem] >= 0 );
        ASSERT( dense.IonHigh[nelem] <= nelem+1 );
        /* IonHigh can be equal to IonLow */
        ASSERT( dense.IonLow[nelem] <= dense.IonHigh[nelem] );

        // Trimming limit on fraction of total charge in system
        trimcharge = 1e-6;

        /* during search phase of mostly neutral matter the electron density
         * can be vastly too large, and the ionization suppressed as a result.
         * during search do not trim down or up as much */
        if( conv.lgSearch )
        {
                trimhi = (realnum)ionbal.trimhi * 1e-4f;
                trimlo = (realnum)ionbal.trimlo * 1e-4f;
        }
        else
        {
                trimhi = (realnum)ionbal.trimhi;
                trimlo = (realnum)ionbal.trimlo;
        }

        /* helium is special case since abundance is so high, and He+ CT with 
         * CO is the dominant CO destruction process in molecular regions */
        if( nelem == ipHELIUM )
        {
                /* never want to trip up a lower stage of ionization */
                trimlo = SMALLFLOAT;

                /* if He+ is highest stage of ionization, probably want to keep it
                 * since important for CO chemistry in molecular clouds */
                if( dense.IonHigh[ipHELIUM] == 1 )
                {
                        trimhi = MIN2( trimhi , 1e-20f );
                }
                else if( dense.IonHigh[ipHELIUM] == 2 )
                {
                        if( conv.lgSearch )
                        {
                                /* during search phase we may be quite far from solution, in the
                                 * case of a PDR sim the electron density may be vastly higher 
                                 * than it will be with stable solution.  He++ can be very important
                                 * for the chemistry and we want to consider it.  Make the
                                 * threshold for ignoring He++ much higher than normal to prevent
                                 * a premature removal of the ion */
                                trimhi = MIN2( trimhi , 1e-17f ); 
                        }
                        else
                        {
                                /* similar smaller upper limit for ion*/
                                trimhi = MIN2( trimhi , 1e-12f ); 
                        }
                }
        }

        /* logic for PDRs, for elements included in chemistry, need stable solutions, 
         * keep 3 ion stages in most cases - added by NA to do HII/PDR sims */
        if( !mole_global.lgNoMole )
        {
                trimlo = SMALLFLOAT;
                if(dense.IonHigh[nelem] ==2)
                {
                        trimhi = MIN2(trimhi, 1e-20f);
                }
        }

        /* raise or lower highest and lowest stages of ionization to
         * consider only significant stages
         * IonHigh[nelem]  stage of ionization  */

        /* sanity check */
        ASSERT( dense.IonLow[nelem] <= dense.IonHigh[nelem] );

        /* this checks on error condition where the gas is stupendously highly ionized,
         * the low limit is already one less than high, and we need to raise the low
         * limit further */
        if( dense.IonHigh[nelem] > 1 &&
                (dense.IonLow[nelem]==dense.IonHigh[nelem]-1) &&
                (dense.xIonDense[nelem][dense.IonLow[nelem]] < dense.density_low_limit) )
        {
#               if 0
                fprintf(ioQQQ,
                        "PROBLEM DISASTER the density of ion %li of element %s is too small to be computed on this cpu.\n",
                        dense.IonLow[nelem]+1,
                        elementnames.chElementName[nelem]);
                fprintf(ioQQQ,
                        "Turn off the element with the command ELEMENT XXX OFF or do not consider "
                        "gas with low density, the current hydrogen density is %.2e cm-3.\n",
                        dense.gas_phase[ipHYDROGEN]);
                fprintf(ioQQQ,
                        "The outer radius of the cloud is %.2e cm - should a stopping "
                        "radius be set?\n",
                        radius.Radius );
                fprintf(ioQQQ,
                        "The abort flag is being set - the calculation is stopping.\n");
#               endif
                //lgAbort = true;
                dense.xIonDense[nelem][dense.IonLow[nelem]] = (realnum)dense.density_low_limit;
                return;
        }

        double itrim = 1.0;
        /* trim down high stages that have too small an abundance */
        while ( ionbal.lgTrimhiOn && 
                          dense.IonHigh[nelem] > dense.IonLow[nelem]  && 
                          ( ( dense.xIonDense[nelem][dense.IonHigh[nelem]]/dense.gas_phase[nelem] <= trimhi*itrim &&
                                  dense.xIonDense[nelem][dense.IonHigh[nelem]] <= trimcharge*dense.EdenTrue ) 
                                 ||
                                 dense.xIonDense[nelem][dense.IonHigh[nelem]] <= dense.density_low_limit )                               
                )
        {
                itrim = 0.125;
                dense.xIonDense[nelem][dense.IonHigh[nelem]-1] += 
                        dense.xIonDense[nelem][dense.IonHigh[nelem]];
                dense.xIonDense[nelem][dense.IonHigh[nelem]] = 0.;
                thermal.setHeating(nelem,dense.IonHigh[nelem]-1,0.);
                long int ipISO = nelem - dense.IonHigh[nelem];
                if ( ipISO>=0 && ipISO<NISO )
                {
                        for( long level = 0; level < iso_sp[ipISO][nelem].numLevels_max; level++ )
                                iso_sp[ipISO][nelem].st[level].Pop() = 0.;
                }
                --dense.IonHigh[nelem];
                lgHi_Down = true;
        }

        /* sanity check */
        ASSERT( dense.IonLow[nelem] <= dense.IonHigh[nelem] );

        itrim = 1.0;
        /* raise lowest stage of ionization, but only if we are near illuminated face of cloud*/
        while( ionbal.lgTrimloOn && 
                (dense.xIonDense[nelem][dense.IonLow[nelem]]/dense.gas_phase[nelem] <= (realnum)trimlo*itrim) && 
                (dense.IonLow[nelem] < (dense.IonHigh[nelem] - 2) ) )
        {
                itrim = 0.125;
                /* raise lowest level of ionization */
                dense.xIonDense[nelem][dense.IonLow[nelem]+1] += 
                        dense.xIonDense[nelem][dense.IonLow[nelem]];
                dense.xIonDense[nelem][dense.IonLow[nelem]] = 0.;
                /* no minus one in below since this is low bound, already bounds at atom */
                thermal.setHeating(nelem,dense.IonLow[nelem],0.);
                long int ipISO = nelem - dense.IonLow[nelem];
                if ( ipISO>=0 && ipISO<NISO )
                {
                        for( long level = 0; level < iso_sp[ipISO][nelem].numLevels_max; level++ )
                                iso_sp[ipISO][nelem].st[level].Pop() = 0.;
                }
                ++dense.IonLow[nelem];
                lgLo_Up = true;
        }

        /* sanity check */
        ASSERT( dense.IonLow[nelem] <= dense.IonHigh[nelem] );

        /* these are standard bounds checks that appear throughout this routine
         * dense.xIonDense[IonLow] is first one with positive abundances
         * 
         * in case where lower ionization stage was just lowered the abundance
         * was set to dense.density_low_limit so test must be < dense.density_low_limit */
        ASSERT( dense.IonLow[nelem] <= 1 ||
                dense.xIonDense[nelem][dense.IonLow[nelem]-1] == 0. );

        {
                /* option to print out what has happened so far .... */
                enum {DEBUG_LOC=false};
                if( DEBUG_LOC && nelem == ipHELIUM )
                {
                        if( lgHi_Down ||lgLo_Up )
                        {
                                fprintf(ioQQQ,"DEBUG TrimZone\t%li\t",nzone );
                                if(  lgHi_Down )
                                {
                                        fprintf(ioQQQ,"high dn %li to %li",
                                                ion_hi_save , 
                                                dense.IonHigh[nelem] );
                                }
                                if( lgLo_Up )
                                {
                                        fprintf(ioQQQ,"low up %li to %li",
                                                ion_lo_save , 
                                                dense.IonLow[nelem] );
                                }
                                fprintf(ioQQQ,"\n" );
                        }
                }
        }

        /* option to print if any trimming occurred */
        if( lgHi_Down || lgLo_Up )
        {
                conv.lgIonStageTrimed = true;
                {
                        /* option to print out what has happened so far .... */
                        enum {DEBUG_LOC=false};
                        if( DEBUG_LOC && nelem==ipHELIUM )
                        {
                                fprintf(ioQQQ,"DEBUG ion_trim zone\t%.2f \t%li\t", fnzone, nelem);
                                if( lgHi_Down  )
                                        fprintf(ioQQQ,"\tHi_Down");
                                if( lgLo_Up )
                                        fprintf(ioQQQ,"\tLo_Up");
                                fprintf(ioQQQ,"\n");
                        }
                }
        }

        /* asserts that that densities of ion stages that are now turned 
         * off are zero */
        for( ion=0; ion<dense.IonLow[nelem]; ++ion )
        {
                ASSERT( dense.xIonDense[nelem][ion] == 0. );
        }
        for( ion=dense.IonHigh[nelem]+1; ion<nelem+1; ++ion )
        {
                ASSERT( dense.xIonDense[nelem][ion] == 0. );
        }

        for( ion=dense.IonLow[nelem]; ion<=dense.IonHigh[nelem]; ++ion )
        {
                /* in case where ionization stage was changed the
                 * density is zero, we set it to SMALLFLOAT since a density
                 * of zero is not possible */
                dense.xIonDense[nelem][ion] = MAX2(dense.xIonDense[nelem][ion], SMALLFLOAT);
        }
        return;
}

void ion_widen(long nelem)
{
        DEBUG_ENTRY( "ion_widen()" );
        if ( dense.lgSetIoniz[nelem] || 
                 ( dense.IonLow[nelem] == 0 && dense.IonHigh[nelem] == nelem+1 ) )
        {
                return;
        }
        double abund = 0.0;
        for (long ion=dense.IonLow[nelem]; ion<=dense.IonHigh[nelem]; ++ion)
        {
                abund += dense.xIonDense[nelem][ion];
        }
        double abundnew = abund;
        if (dense.IonLow[nelem] > 0 )
        {
                --dense.IonLow[nelem];
                dense.xIonDense[nelem][dense.IonLow[nelem]] = (dense.density_low_limit*10.);
                abundnew += (dense.density_low_limit*10.);
                long ipISO = nelem - dense.IonLow[nelem];
                if (ipISO >= 0 && ipISO < NISO)
                        iso_sp[ipISO][nelem].st[0].Pop() = dense.xIonDense[nelem][dense.IonLow[nelem]];
        }
        if ( dense.IonHigh[nelem] < nelem+1)
        {
                ++dense.IonHigh[nelem];
                dense.xIonDense[nelem][dense.IonHigh[nelem]] = (dense.density_low_limit*10.);
                abundnew += (dense.density_low_limit*10.);
                long ipISO = nelem - dense.IonHigh[nelem];
                if (ipISO >= 0 && ipISO < NISO)
                        iso_sp[ipISO][nelem].st[0].Pop() = dense.xIonDense[nelem][dense.IonHigh[nelem]];
        }
        double frac = abund/abundnew;
        for (long ion=dense.IonLow[nelem];ion<=dense.IonHigh[nelem];++ion)
        {
                dense.xIonDense[nelem][ion] *= frac;
        }
}

#ifdef NDEBUG
void ion_trim_validate(long, bool)
{
        (void)0;
}
#else
void ion_trim_validate(long nelem, bool lgIonizTrimCalled)
{
        DEBUG_ENTRY( "ion_trim_validate()" );
        for( long ion=0; ion<dense.IonLow[nelem]; ++ion )
        {
                ASSERT( dense.xIonDense[nelem][ion] == 0. );
        }
        /*if( nelem==5 ) fprintf(ioQQQ,"carbbb\t%li\n", dense.IonHigh[nelem]);*/
        for( long ion=dense.IonLow[nelem]; ion<=dense.IonHigh[nelem]; ++ion )
        {
                /* >>chng 02 feb 06, had been > o., chng to > SMALLFLOAT to
                 * trip over VERY small floats that failed on alphas, but not 386
                 * 
                 * in case where lower ionization stage was just lowered or
                 * trimmed down the abundance
                 * was set to SMALLFLOAT so test must be < SMALLFLOAT */
                /* >>chng 02 feb 19, add check for search phase.  During this search
                 * models with extreme ionization (all neutral or all ionized) can
                 * have extreme but non-zero abundances far from the ionization peak for
                 * element with lots of electrons.  These will go away once the model
                 * becomes stable */
                /* >>chng 03 dec 01, add check on whether ion trim was called 
                 * conserve.in threw assert when iontrim not called and abund grew small */
                ASSERT( conv.lgSearch || !lgIonizTrimCalled ||
                                  /* this can happen if all C is in the form of CO -- 
                                          generalize test to being that at least one ion must survive */
                                  dense.IonLow[nelem] == dense.IonHigh[nelem] ||
                                  dense.xIonDense[nelem][ion] >= SMALLFLOAT || 
                                  dense.xIonDense[nelem][ion]/dense.gas_phase[nelem] >= SMALLFLOAT );
        }
        for( long ion=dense.IonHigh[nelem]+1; ion<=nelem+1; ++ion )
        {
                ASSERT( ion >= 0 );
                ASSERT( dense.xIonDense[nelem][ion] == 0. );
        }
}
#endif