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authorThomas White <taw@physics.org>2019-05-23 16:42:27 +0200
committerThomas White <taw@physics.org>2019-05-29 10:42:14 +0200
commit581f8e8ab1b1d2833fd689540a2758bea1fc93ee (patch)
treef2d0f329ebced450a7451287f3be138ac0aabab5 /src/diffraction-gpu.c
parent1380592a04cba4621341a11cfb9a5526ea9dc4bf (diff)
Normalise sampled spectrum weights to total 1
Diffstat (limited to 'src/diffraction-gpu.c')
-rw-r--r--src/diffraction-gpu.c19
1 files changed, 11 insertions, 8 deletions
diff --git a/src/diffraction-gpu.c b/src/diffraction-gpu.c
index e2bce0cc..4ecf0558 100644
--- a/src/diffraction-gpu.c
+++ b/src/diffraction-gpu.c
@@ -294,8 +294,7 @@ int get_diffraction_gpu(struct gpu_context *gctx, struct image *image,
int n_neg = 0;
int n_nan = 0;
int i;
- double kmin, kmax, step;
- double tot = 0.0;
+ double kmin, kmax, step, norm;
if ( gctx == NULL ) {
ERROR("GPU setup failed.\n");
@@ -341,24 +340,28 @@ int get_diffraction_gpu(struct gpu_context *gctx, struct image *image,
}
spectrum_get_range(image->spectrum, &kmin, &kmax);
- step = (kmax-kmin)/n_samples;
- for ( i=0; i<=n_samples; i++ ) {
+ step = (kmax-kmin)/(n_samples+1);
+
+ /* Determine normalisation factor such that weights add up to 1 after
+ * sampling (bins must have constant width) */
+ for ( i=1; i<=n_samples; i++ ) {
+ double k = kmin + i*step;
+ norm += spectrum_get_density_at_k(image->spectrum, k);
+ }
+ for ( i=1; i<=n_samples; i++ ) {
double k = kmin + i*step;
double prob;
/* Probability = p.d.f. times step width */
- prob = step * spectrum_get_density_at_k(image->spectrum, k);
+ prob = spectrum_get_density_at_k(image->spectrum, k)/norm;
STATUS("Wavelength: %e m, weight = %.5f\n", 1.0/k, prob);
err = do_panels(gctx, image, k, prob, &n_inf, &n_neg, &n_nan);
if ( err ) return 1;
- tot += prob;
-
}
- STATUS("Total weight = %f\n", tot);
if ( n_neg + n_inf + n_nan ) {
ERROR("WARNING: The GPU calculation produced %i negative"