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/*
* diffraction.cl
*
* GPU calculation kernel for truncated lattice diffraction
*
* (c) 2006-2010 Thomas White <taw@physics.org>
*
* Part of CrystFEL - crystallography with a FEL
*
*/
#define INDMAX 70
#define IDIM (INDMAX*2 +1)
float4 quat_rot(float4 q, float4 z)
{
float4 res;
float t01, t02, t03, t11, t12, t13, t22, t23, t33;
t01 = z.x*z.y;
t02 = z.x*z.z;
t03 = z.x*z.w;
t11 = z.y*z.y;
t12 = z.y*z.z;
t13 = z.y*z.w;
t22 = z.z*z.z;
t23 = z.z*z.w;
t33 = z.w*z.w;
res.x = (1.0 - 2.0 * (t22 + t33)) * q.x
+ (2.0 * (t12 + t03)) * q.y
+ (2.0 * (t13 - t02)) * q.z;
res.y = (2.0 * (t12 - t03)) * q.x
+ (1.0 - 2.0 * (t11 + t33)) * q.y
+ (2.0 * (t01 + t23)) * q.z;
res.z = (2.0 * (t02 + t13)) * q.x
+ (2.0 * (t23 - t01)) * q.y
+ (1.0 - 2.0 * (t11 + t22)) * q.z;
return res;
}
float4 get_q(int x, int y, float cx, float cy, float res, float clen, float k,
float *ttp, float4 z, int sampling)
{
float rx, ry, r;
float ttx, tty, tt;
float4 q;
rx = ((float)x - sampling*cx)/(res*sampling);
ry = ((float)y - sampling*cy)/(res*sampling);
r = sqrt(pow(rx, 2.0) + pow(ry, 2.0));
ttx = atan2(rx, clen);
tty = atan2(ry, clen);
tt = atan2(r, clen);
*ttp = tt;
q = (float4)(k*sin(ttx), k*sin(tty), k-k*cos(tt), 0.0);
return quat_rot(q, z);
}
float lattice_factor(float16 cell, float4 q, int4 ncells)
{
float f1, f2, f3;
float4 Udotq;
const int na = ncells.s0;
const int nb = ncells.s1;
const int nc = ncells.s2;
Udotq.x = cell.s0*q.x + cell.s1*q.y + cell.s2*q.z;
Udotq.y = cell.s3*q.x + cell.s4*q.y + cell.s5*q.z;
Udotq.z = cell.s6*q.x + cell.s7*q.y + cell.s8*q.z;
/* At exact Bragg condition, f1 = na */
f1 = sin(M_PI*(float)na*Udotq.x) / sin(M_PI*Udotq.x);
/* At exact Bragg condition, f2 = nb */
f2 = sin(M_PI*(float)nb*Udotq.y) / sin(M_PI*Udotq.y);
/* At exact Bragg condition, f3 = nc */
f3 = sin(M_PI*(float)nc*Udotq.z) / sin(M_PI*Udotq.z);
/* At exact Bragg condition, this will multiply the molecular
* part of the structure factor by the number of unit cells,
* as desired (more scattering from bigger crystal!) */
return f1 * f2 * f3;
}
float2 get_sfac(global float2 *sfacs, float16 cell, float4 q)
{
float hf, kf, lf;
int h, k, l;
int idx;
hf = cell.s0*q.x + cell.s1*q.y + cell.s2*q.z; /* h */
kf = cell.s3*q.x + cell.s4*q.y + cell.s5*q.z; /* k */
lf = cell.s6*q.x + cell.s7*q.y + cell.s8*q.z; /* l */
h = round(hf);
k = round(kf);
l = round(lf);
if ( (abs(h) > INDMAX) || (abs(k) > INDMAX) || (abs(l) > INDMAX) ) {
return 100.0;
}
if ( h < 0 ) h += IDIM;
if ( k < 0 ) k += IDIM;
if ( l < 0 ) l += IDIM;
if ( (h>=IDIM) || (k>=IDIM) || (l>=IDIM) ) return 100.0;
idx = h + (IDIM*k) + (IDIM*IDIM*l);
return sfacs[idx];
}
kernel void diffraction(global float2 *diff, global float *tt, float k,
int w, float cx, float cy,
float res, float clen, float16 cell,
global float2 *sfacs, float4 z, int4 ncells,
int xmin, int ymin, int sampling, local float2 *tmp)
{
float ttv;
const int x = get_global_id(0) + (xmin*sampling);
const int y = get_global_id(1) + (ymin*sampling);
float f_lattice;
float2 f_molecule;
float4 q;
const int lx = get_local_id(0);
const int ly = get_local_id(1);
const int ax = x / sampling;
const int ay = y / sampling;
/* Calculate value */
q = get_q(x, y, cx, cy, res, clen, k, &ttv, z, sampling);
f_lattice = lattice_factor(cell, q, ncells);
f_molecule = get_sfac(sfacs, cell, q);
/* Write the value to local memory */
tmp[lx+sampling*ly] = f_molecule * f_lattice;
/* Memory fence */
barrier(CLK_LOCAL_MEM_FENCE);
/* Leader thread sums the values */
if ( lx + ly == 0 ) {
int i;
float2 sum = (0.0, 0.0);
for ( i=0; i<sampling*sampling; i++ ) sum += tmp[i];
diff[ax+w*ay] = sum / (sampling*sampling);
/* Leader thread also records the 2theta value.
* This should really be averaged across all pixels, but
* I strongly suspect this would be a waste of time. */
tt[ax+w*ay] = ttv;
}
}
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