From 0f6ebe5649902dea9456c6598bc28e694c422336 Mon Sep 17 00:00:00 2001
From: Thomas White <taw@physics.org>
Date: Tue, 9 Feb 2010 17:24:16 +0100
Subject: Use OpenCL for much faster diffraction calculation

---
 data/Makefile.am    |   2 +-
 data/diffraction.cl | 106 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 107 insertions(+), 1 deletion(-)
 create mode 100644 data/diffraction.cl

(limited to 'data')

diff --git a/data/Makefile.am b/data/Makefile.am
index b4cebb2d..b55597f0 100644
--- a/data/Makefile.am
+++ b/data/Makefile.am
@@ -2,4 +2,4 @@ hdfseedir = $(datadir)/hdfsee
 hdfsee_DATA = displaywindow.ui
 
 crystfeldir = $(datadir)/crystfel
-crystfel_DATA = sfac/*
+crystfel_DATA = sfac/* diffraction.cl
diff --git a/data/diffraction.cl b/data/diffraction.cl
new file mode 100644
index 00000000..5c75d70b
--- /dev/null
+++ b/data/diffraction.cl
@@ -0,0 +1,106 @@
+/*
+ * 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 30
+#define IDIM (INDMAX*2 +1)
+
+
+float4 get_q(int x, int y, float cx, float cy, float res, float clen, float k,
+             float *ttp)
+{
+	float rx, ry, r;
+	float ttx, tty, tt;
+
+	rx = ((float)x - cx)/res;
+	ry = ((float)y - cy)/res;
+
+	r = sqrt(pow(rx, 2.0) + pow(ry, 2.0));
+
+	ttx = atan2(rx, clen);
+	tty = atan2(ry, clen);
+	tt = atan2(r, clen);
+
+	*ttp = tt;
+
+	return (float4)(k*sin(ttx), k*sin(tty), k-k*cos(tt), 0.0);
+}
+
+
+float lattice_factor(float16 cell, float4 q)
+{
+	float f1, f2, f3;
+	float4 Udotq;
+	const int na = 8;
+	const int nb = 8;
+	const int nc = 8;
+
+	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)
+{
+	signed int h, k, l;
+	int idx;
+
+	h = rint(cell.s0*q.x + cell.s1*q.y + cell.s2*q.z);  /* h */
+	k = rint(cell.s3*q.x + cell.s4*q.y + cell.s5*q.z);  /* k */
+	l = rint(cell.s6*q.x + cell.s7*q.y + cell.s8*q.z);  /* l */
+
+	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;
+
+	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)
+{
+	float ttv;
+	const int x = get_global_id(0);
+	const int y = get_global_id(1);
+	float f_lattice;
+	float2 f_molecule;
+
+	float4 q = get_q(x, y, cx, cy, res, clen, k, &ttv);
+
+	f_lattice = lattice_factor(cell, q);
+	f_molecule = get_sfac(sfacs, cell, q);
+
+	diff[x+w*y] = f_molecule*f_lattice;
+	tt[x+w*y] = ttv;
+}
-- 
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