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/*!
* \file
* \brief Implementation of numerical integration
* \author Tony Ottosson
*
* -------------------------------------------------------------------------
*
* IT++ - C++ library of mathematical, signal processing, speech processing,
* and communications classes and functions
*
* Copyright (C) 1995-2008 (see AUTHORS file for a list of contributors)
*
* 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* -------------------------------------------------------------------------
*/
#include <itpp/base/math/integration.h>
#include <itpp/base/math/elem_math.h>
#include <itpp/base/help_functions.h>
#include <itpp/base/matfunc.h>
#include <itpp/base/specmat.h>
namespace itpp {
//! quadstep function
double quadstep(double (*f)(double), double a, double b,
double fa, double fm, double fb, double is)
{
double Q, m, h, fml, fmr, i1, i2;
vec x(2), y(2);
m = (a+b)/2; h = (b-a)/4;
x = vec_2(a+h, b-h);
y = apply_function<double>(f, x);
fml = y(0); fmr = y(1);
i1 = h/1.5 * (fa + 4*fm + fb);
i2 = h/3 * (fa + 4*(fml + fmr) + 2*fm + fb);
i1 = (16*i2 - i1)/15;
if( (is + (i1-i2) == is) || (m<=a) || (b<=m) ) {
if( (m <= a) || (b<=m) ) {
it_warning("Interval contains no more machine number. Required tolerance may not be met");
}
Q = i1;
return Q;
} else {
Q = quadstep(f, a, m, fa, fml, fm, is) + quadstep(f, m, b, fm, fmr, fb, is);
}
return Q;
}
double quad(double (*f)(double), double a, double b, double tol)
{
vec x(3), y(3), yy(5);
double Q, fa, fm, fb, is;
x = vec_3(a, (a+b)/2, b);
y = apply_function<double>(f, x);
fa = y(0); fm = y(1); fb = y(2);
yy = apply_function<double>(f, a + vec(".9501 .2311 .6068 .4860 .8913")
* (b - a));
is = (b-a)/8*(sum(y)+sum(yy));
if (is == 0.0)
is = b-a;
is = is*tol/std::numeric_limits<double>::epsilon();
Q = quadstep(f, a, b, fa, fm, fb, is);
return Q;
}
//--------------------- quadl() ----------------------------------------
//! quadlstep function
double quadlstep(double (*f)(double), double a, double b,
double fa, double fb, double is)
{
double Q, h, m, alpha, beta, mll, ml, mr, mrr, fmll, fml, fm, fmr, fmrr,
i1, i2;
vec x(5), y(5);
h=(b-a)/2; m=(a+b)/2;
alpha = std::sqrt(2.0/3); beta = 1.0/std::sqrt(5.0);
mll=m-alpha*h; ml=m-beta*h; mr=m+beta*h; mrr=m+alpha*h;
x(0)=mll; x(1) = ml; x(2) = m; x(3) = mr; x(4) = mrr;
y = apply_function<double>(f, x);
fmll=y(0); fml=y(1); fm=y(2); fmr=y(3); fmrr=y(4);
i2 = (h/6)*(fa+fb+5*(fml+fmr));
i1 = (h/1470)*(77*(fa+fb)+432*(fmll+fmrr)+625*(fml+fmr)+672*fm);
if( (is + (i1-i2) == is) || (mll<=a) || (b<=mrr) ) {
if( (m <= a) || (b<=m) ) {
it_warning("Interval contains no more machine number. Required tolerance may not be met");
}
Q = i1;
return Q;
} else {
Q=quadlstep(f, a, mll, fa, fmll, is) + quadlstep(f, mll, ml, fmll, fml, is) + quadlstep(f, ml, m, fml, fm, is) +
quadlstep(f, m, mr, fm, fmr, is) + quadlstep(f, mr, mrr, fmr, fmrr, is) + quadlstep(f, mrr, b, fmrr, fb, is);
}
return Q;
}
double quadl(double (*f)(double), double a, double b, double tol)
{
double Q, m, h, alpha, beta, x1, x2, x3, fa, fb, i1, i2, is, s, erri1, erri2, R;
vec x(13), y(13);
double tol2 = tol;
m=(a+b)/2; h=(b-a)/2;
alpha = std::sqrt(2.0/3); beta = 1.0/std::sqrt(5.0);
x1=.942882415695480; x2=.641853342345781; x3=.236383199662150;
x(0)=a; x(1)=m-x1*h; x(2)=m-alpha*h; x(3)=m-x2*h;
x(4)=m-beta*h; x(5)=m-x3*h; x(6)=m; x(7)=m+x3*h;
x(8)=m+beta*h; x(9)=m+x2*h; x(10)=m+alpha*h;
x(11)=m+x1*h; x(12)=b;
y = apply_function<double>(f, x);
fa=y(0); fb=y(12);
i2=(h/6)*(y(0)+y(12)+5*(y(4)+y(8)));
i1=(h/1470)*(77*(y(0)+y(12))+432*(y(2)+y(10))+ 625*(y(4)+y(8))+672*y(6));
is=h*(.0158271919734802*(y(0)+y(12))+.0942738402188500*(y(1)+y(11))+.155071987336585*(y(2)+y(10))+
.188821573960182*(y(3)+y(9))+.199773405226859 *(y(4)+y(8))+.224926465333340*(y(5)+y(7))+.242611071901408*y(6));
s = sign(is);
if (s == 0.0)
s = 1;
erri1 = std::abs(i1-is);
erri2 = std::abs(i2-is);
R=1;
if (erri2 != 0.0)
R = erri1/erri2;
if (R>0 && R<1)
tol2=tol2/R;
is = s*std::abs(is)*tol2/std::numeric_limits<double>::epsilon();
if (is == 0.0)
is=b-a;
Q = quadlstep(f, a, b, fa, fb, is);
return Q;
}
} // namespace itpp
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