Category : C Source Code
Archive : CEPHES22.ZIP
Filename : REMESS.C
Output of file : REMESS.C contained in archive : CEPHES22.ZIP
#include "remes.h"
/* Search subroutine */
remess()
{
double a, b, q, xm, ym, xn, yn, xx0, xx1;
int i, j, meq, emsign, ensign, steps;
double approx(), func(), geterr();
/* Search for maxima of error */
eclose = 1e30;
farther = 0.0;
j = 0;
meq = neq;
if( (d > 0) || ((config & ZER) != 0) )
{
j = 1;
meq += 1;
}
xx0 = apstrt;
for( i=0; i
steps = 0;
if( (d > 0) || ((config & ZER) != 0) )
xx1 = xx[i]; /* Next zero */
else
xx1 = mm[i+1]; /* Next maximum */
if( i == meq-1 )
xx1 = apend;
xm = mm[i];
ym = geterr(xm);
emsign = esign; /* Sign of error */
q = step[i];
xn = xm + q;
/* Cannot skip over adjacent boundaries */
if( xn < xx0 )
goto revers;
if( xn >= xx1 )
goto revers;
yn = geterr(xn);
ensign = esign;
if( yn < ym )
{
revers:
q = -q;
xn = xm;
yn = ym;
ensign = emsign;
}
/* March until error becomes smaller. */
while( yn >= ym )
{
if( ++steps > 10 )
goto tsear;
ym = yn;
xm = xn;
emsign = ensign;
a = xm + q;
if( a == xm )
goto tsear;
/* Must not skip over the zeros either side. */
if( a <= xx0 )
goto tsear;
if( a >= xx1 )
goto tsear;
xn = a;
yn = geterr(xn);
ensign = esign;
}
tsear:
mm[i] = xm; /* Position of maximum */
yy[i] = ym; /* Value of maximum */
if( ym == 0.0 )
printf( "yy[%d] = 0\n", i );
if( eclose > ym )
eclose = ym;
if( farther < ym )
farther = ym;
/* No denominator */
if( (d == 0) && ((config & ZER) == 0) )
xx[i] = xm;
/* Walk to next zero. */
if( (d > 0) || ((config & ZER) != 0) )
xx0 = xx1;
else
xx0 = 0.5*(xm + xx1);
} /* end of search loop */
/* Decrease step size if error spread increased. */
q = (farther - eclose);
/* Relative error spread */
if( eclose != 0.0 )
q /= eclose;
if( q >= spread )
{ /* Spread is increasing; decrease step size. */
if( config & TRUNC )
delta *= 0.875;
else
delta *= 0.5;
printf( "delta = %.4E\n", delta );
}
spread = q;
printf( "peak error = %.4E, relative error spread = %.4E\n",
farther, spread );
/* Calculate new step sizes */
if( (d == 0) && ((config & ZER) == 0) )
{
if( spread < 0.25 )
q = 0.0625;
else
q = 0.5;
for( i=0; i
}
else
{
for( i=0; i
q = yy[i+1];
if( q != 0.0 )
q = yy[i]/q - 1.0;
else
q = 0.0625;
if( q > 0.25 )
q = 0.25;
q *= mm[i+1] - mm[i];
step[i] = q * delta;
}
step[neq] = step[neq-1];
/* Insert new locations for the zeros. */
for( i=0; i
xm = xx[i] - step[i];
if( xm <= apstrt )
continue;
if( xm >= apend )
continue;
if( xm <= mm[i] )
{
printf( "xx[%d] < mm\n", i );
xm = 0.5 * (mm[i] + xx[i]);
}
if( xm >= mm[i+1] )
{
printf( "xx[%d] > mm\n", i );
xm = 0.5 * (mm[i+1] + xx[i]);
}
xx[i] = xm;
}
}
sdone: ;
}
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