source: sasview/sansmodels/src/sans/models/c_extensions/refl.c @ 6cda91f

/**
 * Scattering model for a sphere
 */

#include <math.h>
#include "refl.h"
#include <stdio.h>
#include <stdlib.h>

#define lamda 4.62

typedef struct {
        double re;
        double im;
} complex;

typedef struct {
        complex a;
        complex b;
        complex c;
        complex d;
} matrix;

complex cassign(real, imag)
        double real, imag;
{
        complex x;
        x.re = real;
        x.im = imag;
        return x;
}


complex cadd(x,y)
        complex x,y;
{
        complex z;
        z.re = x.re + y.re;
        z.im = x.im + y.im;
        return z;
}

complex rcmult(x,y)
        double x;
    complex y;
{
        complex z;
        z.re = x*y.re;
        z.im = x*y.im;
        return z;
}

complex csub(x,y)
        complex x,y;
{
        complex z;
        z.re = x.re - y.re;
        z.im = x.im - y.im;
        return z;
}


complex cmult(x,y)
        complex x,y;
{
        complex z;
        z.re = x.re*y.re - x.im*y.im;
        z.im = x.re*y.im + x.im*y.re;
        return z;
}

complex cdiv(x,y)
        complex x,y;
{
        complex z;
        z.re = (x.re*y.re + x.im*y.im)/(y.re*y.re + y.im*y.im);
        z.im = (x.im*y.re - x.re*y.im)/(y.re*y.re + y.im*y.im);
        return z;
}

complex cexp(b)
        complex b;
{
        complex z;
        double br,bi;
        br=b.re;
        bi=b.im;
        z.re = exp(br)*cos(bi);
        z.im = exp(br)*sin(bi);
        return z;
}


complex csqrt(z)   /* see Schaum`s Math Handbook p. 22, 6.6 and 6.10 */
        complex z;
{
        complex c;
        double zr,zi,x,y,r,w;

        zr=z.re;
        zi=z.im;

        if (zr==0.0 && zi==0.0)
        {
    c.re=0.0;
        c.im=0.0;
    return c;
        }
        else
        {
                x=fabs(zr);
                y=fabs(zi);
                if (x>y)
                {
                        r=y/x;
                        w=sqrt(x)*sqrt(0.5*(1.0+sqrt(1.0+r*r)));
                }
                else
                {
                        r=x/y;
                        w=sqrt(y)*sqrt(0.5*(r+sqrt(1.0+r*r)));
                }
                if (zr >=0.0)
                {
                        c.re=w;
                        c.im=zi/(2.0*w);
                }
                else
                {
                        c.im=(zi >= 0) ? w : -w;
                        c.re=zi/(2.0*c.im);
                }
                return c;
        }
}

complex ccos(b)
        complex b;
{
        complex neg,negb,zero,two,z,i,bi,negbi;
        zero = cassign(0.0,0.0);
        two = cassign(2.0,0.0);
        i = cassign(0.0,1.0);
        bi = cmult(b,i);
        negbi = csub(zero,bi);
        z = cdiv(cadd(cexp(bi),cexp(negbi)),two);
        return z;
}

double errfunc(n_sub, i)
        double n_sub;
        int i;
{
        double bin_size, ind, func;
        ind = i;
        // i range = [ -4..4], x range = [ -2.5..2.5]
        bin_size = n_sub/2.0/2.5;  //size of each sub-layer
        // rescale erf so that 0 < erf < 1 in -2.5 <= x <= 2.5
        func = (erf(ind/bin_size)/2.0+0.5);
        return func;
}

double linefunc(n_sub, i)
        double n_sub;
        int i;
{
        double bin_size, ind, func;
        ind = i + 0.5;
        // i range = [ -4..4], x range = [ -2.5..2.5]
        bin_size = 1.0/n_sub;  //size of each sub-layer
        // rescale erf so that 0 < erf < 1 in -2.5 <= x <= 2.5
        func = ((ind + floor(n_sub/2.0))*bin_size);
        return func;
}

double parabolic_r(n_sub, i)
        double n_sub;
        int i;
{
        double bin_size, ind, func;
        ind = i + 0.5;
        // i range = [ -4..4], x range = [ 0..1]
        bin_size = 1.0/n_sub;  //size of each sub-layer; n_sub = 0 is a singular point (error)
        func = ((ind + floor(n_sub/2.0))*bin_size)*((ind + floor(n_sub/2.0))*bin_size);
        return func;
}

double parabolic_l(n_sub, i)
        double n_sub;
        int i;
{
        double bin_size,ind, func;
        ind = i + 0.5;
        bin_size = 1.0/n_sub;  //size of each sub-layer; n_sub = 0 is a singular point (error)
        func =1.0-(((ind + floor(n_sub/2.0))*bin_size) - 1.0) *(((ind + floor(n_sub/2.0))*bin_size) - 1.0);
        return func;
}

double cubic_r(n_sub, i)
        double n_sub;
        int i;
{
        double bin_size,ind, func;
        ind = i + 0.5;
        // i range = [ -4..4], x range = [ 0..1]
        bin_size = 1.0/n_sub;  //size of each sub-layer; n_sub = 0 is a singular point (error)
        func = ((ind+ floor(n_sub/2.0))*bin_size)*((ind + floor(n_sub/2.0))*bin_size)*((ind + floor(n_sub/2.0))*bin_size);
        return func;
}

double cubic_l(n_sub, i)
        double n_sub;
        int i;
{
        double bin_size,ind, func;
        ind = i + 0.5;
        bin_size = 1.0/n_sub;  //size of each sub-layer; n_sub = 0 is a singular point (error)
        func = 1.0+(((ind + floor(n_sub/2.0)))*bin_size - 1.0)*(((ind + floor(n_sub/2.0)))*bin_size - 1.0)*(((ind + floor(n_sub/2.0)))*bin_size - 1.0);
        return func;
}

double interfunc(fun_type, n_sub, i, sld_l, sld_r)
        double n_sub, sld_l, sld_r;
        int fun_type, i;
{
        double sld_i, func;
        switch(fun_type){
                case 1 :
                        func = linefunc(n_sub, i);
                        break;
                case 2 :
                        func = parabolic_r(n_sub, i);
                        break;
                case 3 :
                        func = parabolic_l(n_sub, i);
                        break;
                case 4 :
                        func = cubic_r(n_sub, i);
                        break;
                case 5 :
                        func = cubic_l(n_sub, i);
                        break;
                default:
                        func = errfunc(n_sub, i);
                        break;
        }
        if (sld_r>sld_l){
                sld_i = (sld_r-sld_l)*func+sld_l; //sld_cal(sld[i],sld[i+1],n_sub,dz,thick);
        }
        else if (sld_r<sld_l){
                func = 1.0-func;
                sld_i = (sld_l-sld_r)*func+sld_r; //sld_cal(sld[i],sld[i+1],n_sub,dz,thick);
        }
        else{
                sld_i = sld_r;
        }
        return sld_i;
}

double re_kernel(double dp[], double q) {
        int n = dp[0];
        int i,j,fun_type[n+2];

        double scale = dp[1];
        double thick_inter_sub = dp[2];
        double sld_sub = dp[4];
        double sld_super = dp[5];
        double background = dp[6];

        double sld[n+2],sld_im[n+2],thick_inter[n+2],thick[n+2],total_thick;
        fun_type[0] = dp[3];
        for (i =1; i<=n; i++){
                sld[i] = dp[i+6];
                thick_inter[i]= dp[i+16];
                thick[i] = dp[i+26];
                fun_type[i] = dp[i+36];
                sld_im[i] = dp[i+46];

                total_thick += thick[i] + thick_inter[i];
        }
        sld[0] = sld_sub;
        sld[n+1] = sld_super;
        sld_im[0] = fabs(dp[0+56]);
        sld_im[n+1] = fabs(dp[1+56]);
        thick[0] = total_thick/5.0;
        thick[n+1] = total_thick/5.0;
        thick_inter[0] = thick_inter_sub;
        thick_inter[n+1] = 0.0;

        double nsl=21.0; //nsl = Num_sub_layer:  MUST ODD number in double //no other number works now
        int n_s, floor_nsl;
    double sld_i,sldim_i,dz,phi,R,ko2;
    double sign,erfunc;
    double pi;
        complex  inv_n,phi1,alpha,alpha2,kn,fnm,fnp,rn,Xn,nn,nn2,an,nnp1,one,zero,two,n_sub,n_sup,knp1,Xnp1;
        pi = 4.0*atan(1.0);
    one = cassign(1.0,0.0);
        //zero = cassign(0.0,0.0);
        two= cassign(0.0,-2.0);

        floor_nsl = floor(nsl/2.0);

        //Checking if floor is available.
        //no imaginary sld inputs in this function yet
    n_sub=cassign(1.0-sld_sub*pow(lamda,2.0)/(2.0*pi),pow(lamda,2.0)/(2.0*pi)*sld_im[0]);
    n_sup=cassign(1.0-sld_super*pow(lamda,2.0)/(2.0*pi),pow(lamda,2.0)/(2.0*pi)*sld_im[n+1]);
    ko2 = pow(2.0*pi/lamda,2.0);

    phi = asin(lamda*q/(4.0*pi));
    phi1 = cdiv(rcmult(phi,one),n_sup);
    alpha = cmult(n_sup,ccos(phi1));
        alpha2 = cmult(alpha,alpha);

    nnp1=n_sub;
    knp1=csqrt(rcmult(ko2,csub(cmult(nnp1,nnp1),alpha2)));  //nnp1*ko*sin(phinp1)
    Xnp1=cassign(0.0,0.0);
    dz = 0.0;
    // iteration for # of layers +sub from the top
    for (i=1;i<=n+1; i++){
                //iteration for 9 sub-layers
                for (j=0;j<2;j++){
                        for (n_s=-floor_nsl;n_s<=floor_nsl; n_s++){
                                if (j==1){
                                        if (i==n+1)
                                                break;
                                        dz = thick[i];
                                        sld_i = sld[i];
                                        sldim_i = sld_im[i];
                                }
                                else{
                                        dz = thick_inter[i-1]/nsl;
                                        if (sld[i-1] == sld[i]){
                                                sld_i = sld[i];
                                        }
                                        else{
                                                sld_i = interfunc(fun_type[i-1],nsl, n_s, sld[i-1], sld[i]);
                                        }
                                        if (sld_im[i-1] == sld_im[i]){
                                                sldim_i = sld_im[i];
                                        }
                                        else{
                                                sldim_i = interfunc(fun_type[i-1],nsl, n_s, sld_im[i-1], sld_im[i]);
                                        }
                                }
                                nn = cassign(1.0-sld_i*pow(lamda,2.0)/(2.0*pi),pow(lamda,2.0)/(2.0*pi)*sldim_i);
                                nn2=cmult(nn,nn);

                                kn=csqrt(rcmult(ko2,csub(nn2,alpha2)));        //nn*ko*sin(phin)
                                an=cexp(rcmult(dz,cmult(two,kn)));

                                fnm=csub(kn,knp1);
                                fnp=cadd(kn,knp1);
                                rn=cdiv(fnm,fnp);
                                Xn=cmult(an,cdiv(cadd(rn,Xnp1),cadd(one,cmult(rn,Xnp1))));    //Xn=an*((rn+Xnp1*anp1)/(1+rn*Xnp1*anp1))

                                Xnp1=Xn;
                                knp1=kn;

                                if (j==1)
                                        break;
                        }
                }
    }
    R=pow(Xn.re,2.0)+pow(Xn.im,2.0);
    // This temperarily fixes the total reflection for Rfunction and linear.
    // ToDo: Show why it happens that Xn.re=0 and Xn.im >1!
    if (Xn.im == 0.0){
        R=1.0;
    }
    R *= scale;
    R += background;

    return R;

}
/**
 * Function to evaluate 1D scattering function
 * @param pars: parameters of the sphere
 * @param q: q-value
 * @return: function value
 */
double refl_analytical_1D(ReflParameters *pars, double q) {
        double dp[59];

        dp[0] = pars->n_layers;
        dp[1] = pars->scale;
        dp[2] = pars->thick_inter0;
        dp[3] = pars->func_inter0;
        dp[4] = pars->sld_sub0;
        dp[5] = pars->sld_medium;
        dp[6] = pars->background;

        dp[7] = pars->sld_flat1;
        dp[8] = pars->sld_flat2;
        dp[9] = pars->sld_flat3;
        dp[10] = pars->sld_flat4;
        dp[11] = pars->sld_flat5;
        dp[12] = pars->sld_flat6;
        dp[13] = pars->sld_flat7;
        dp[14] = pars->sld_flat8;
        dp[15] = pars->sld_flat9;
        dp[16] = pars->sld_flat10;

        dp[17] = pars->thick_inter1;
        dp[18] = pars->thick_inter2;
        dp[19] = pars->thick_inter3;
        dp[20] = pars->thick_inter4;
        dp[21] = pars->thick_inter5;
        dp[22] = pars->thick_inter6;
        dp[23] = pars->thick_inter7;
        dp[24] = pars->thick_inter8;
        dp[25] = pars->thick_inter9;
        dp[26] = pars->thick_inter10;

        dp[27] = pars->thick_flat1;
        dp[28] = pars->thick_flat2;
        dp[29] = pars->thick_flat3;
        dp[30] = pars->thick_flat4;
        dp[31] = pars->thick_flat5;
        dp[32] = pars->thick_flat6;
        dp[33] = pars->thick_flat7;
        dp[34] = pars->thick_flat8;
        dp[35] = pars->thick_flat9;
        dp[36] = pars->thick_flat10;

        dp[37] = pars->func_inter1;
        dp[38] = pars->func_inter2;
        dp[39] = pars->func_inter3;
        dp[40] = pars->func_inter4;
        dp[41] = pars->func_inter5;
        dp[42] = pars->func_inter6;
        dp[43] = pars->func_inter7;
        dp[44] = pars->func_inter8;
        dp[45] = pars->func_inter9;
        dp[46] = pars->func_inter10;

        dp[47] = pars->sldIM_flat1;
        dp[48] = pars->sldIM_flat2;
        dp[49] = pars->sldIM_flat3;
        dp[50] = pars->sldIM_flat4;
        dp[51] = pars->sldIM_flat5;
        dp[52] = pars->sldIM_flat6;
        dp[53] = pars->sldIM_flat7;
        dp[54] = pars->sldIM_flat8;
        dp[55] = pars->sldIM_flat9;
        dp[56] = pars->sldIM_flat10;

        dp[57] = pars->sldIM_sub0;
        dp[58] = pars->sldIM_medium;

        return re_kernel(dp, q);
}

/**
 * Function to evaluate 2D scattering function
 * @param pars: parameters of the sphere
 * @param q: q-value
 * @return: function value
 */
double refl_analytical_2D(ReflParameters *pars, double q, double phi) {
        return refl_analytical_1D(pars,q);
}

double refl_analytical_2DXY(ReflParameters *pars, double qx, double qy){
        return refl_analytical_1D(pars,sqrt(qx*qx+qy*qy));
}