Files
Jungfraujoch/image_analysis/scale_merge/StillsPartialityRefine.cpp
T
leonarski_fandClaude Opus 5.5 b440e3792b StillsPartialityRefine: measure the run width only on shells with signal
Without a resolution limit the outer d*^2 shells of the width measurement lie beyond the diffraction
limit, where the summed intensity is noise or even negative; one such shell made the whole measurement
fail, and 5 of 11 still-battery sets (sacla237, pal86, pal90, lcls242_s, lcls242_t) fell back to the
per-crystal window fit. A shell now enters the fit only where its summed intensity is measured to 10 %
(sum I / sigma >= 10), and at least three shells are needed.

Weighting the fit by the shells' signal instead was tried and rejected: it lets the strong low-resolution
shells set the width alone, and on the MicroMAX pink set the dimple R-free went 0.2442 -> 0.2748.

The matrix subsets, which are cut at their resolution, are unchanged within 0.0010 dimple R-free
(SwissFEL 0.2453, -C/-S 0.2513, mono 0.3188, pink 0.2442, SACLA 243 0.2455, SACLA 237 0.2327,
LCLS 222 0.2335, PAL 86 0.3628).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CeEGgpKdfkCTJb3YNMJcu
2026-10-21 21:23:28 +02:00

590 lines
29 KiB
C++

// SPDX-FileCopyrightText: 2025 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only
#include "StillsPartialityRefine.h"
#include <algorithm>
#include <array>
#include <atomic>
#include <cmath>
#include <future>
#include <thread>
#include <vector>
#include <Eigen/Dense>
#include <ceres/rotation.h>
#include "Merge.h"
#include "../../common/Logger.h"
#include "../../common/ThreadAffinity.h"
namespace {
constexpr size_t MIN_FIT_REFLECTIONS = 20;
constexpr double kRadToDeg = 180.0 / 3.14159265358979323846;
double SafeInv(double x, double fallback) {
if (!std::isfinite(x) || x == 0.0)
return fallback;
return 1.0 / x;
}
// One accepted reflection reduced to the physical partiality fit: the base reciprocal vector q (crystal
// frame at the stored per-image orientation), the reference full intensity, the measured intensity, the
// reciprocal of the prescaling correction (the factor that turns a true intensity back into counts)
// and the weight. dist_ewald / partiality are recomputed from q under the refined tilt.
struct FitObs {
double qx, qy, qz;
double Iref;
double Iobs;
double inv_corr; // 1 / (prescaling_corr * qe_corr * flight_corr)
double weight; // 1 / sigma
};
double VecLen(double x, double y, double z) { return std::sqrt(x * x + y * y + z * z); }
// Analytic partiality for a reflection whose base reciprocal vector is q, tilted by (psi_x, psi_y).
// Mirrors BraggPrediction: dist_ewald = |S| - 1/lambda with S = q_rot + S0, and
// p = exp(-dist_ewald^2 / 2 sigma^2), sigma^2 = gamma0^2 + (gamma_e*d*)^2 + (bw*|q_z|)^2 - three
// independent broadenings added in quadrature: the reciprocal-lattice point's own radius (gamma0,
// ~1/domain size, resolution-INdependent), the mosaic/divergence spread (gamma_e*d*, proportional to
// d*) and the bandwidth smear along the beam. In practice the fit below returns gamma_e ~ 0 and the
// width is essentially gamma0 - see there.
double ComputeP(double qx, double qy, double qz,
double psi_x, double psi_y,
double s0x, double s0y, double s0z, double inv_lambda,
double gamma0, double gamma_e, double bw) {
double aa[3] = {psi_x, psi_y, 0.0};
double q[3] = {qx, qy, qz};
double qr[3];
ceres::AngleAxisRotatePoint(aa, q, qr);
const double Sx = qr[0] + s0x, Sy = qr[1] + s0y, Sz = qr[2] + s0z;
const double de = std::sqrt(Sx * Sx + Sy * Sy + Sz * Sz) - inv_lambda;
const double dstar = std::sqrt(qr[0] * qr[0] + qr[1] * qr[1] + qr[2] * qr[2]);
const double sig_ang = gamma_e * dstar;
const double sbw = bw * std::fabs(qr[2]);
const double sig2 = gamma0 * gamma0 + sig_ang * sig_ang + sbw * sbw;
if (!(sig2 > 0.0))
return 1.0;
return std::exp(-0.5 * de * de / sig2);
}
// The prediction window cuts the rocking curve. Reflections fill a window of half-width W evenly, so
// their plain moment of de is u = W^2 / 3, and the intensity-weighted moment m of a Gaussian of width
// s cut at +-W is u * g(a), a = W / s, with g(a) = 3/a^2 (1 - 2 a phi(a) / erf(a / sqrt 2)): 1 for a
// curve much wider than the window, s^2 / u for a much narrower one. Solves g(a) = m / u for s^2 by
// bisection (g falls with a). A curve wider than the window cannot be measured through it, so it is
// taken as wide as the window (a = 1).
double UntruncatedVariance(double m, double u) {
auto g = [](double a) {
const double phi = std::exp(-0.5 * a * a) / std::sqrt(2.0 * 3.14159265358979323846);
return 3.0 / (a * a) * (1.0 - 2.0 * a * phi / std::erf(a / std::sqrt(2.0)));
};
const double t = m / u;
double lo = 1.0, hi = 50.0;
if (!(t < g(lo)))
return 3.0 * u;
for (int i = 0; i < 60; ++i) {
const double mid = 0.5 * (lo + hi);
(g(mid) > t ? lo : hi) = mid;
}
const double a = 0.5 * (lo + hi);
return 3.0 * u / (a * a);
}
// Robust per-crystal scale G (linear in G given the model coefficients), identical objective to
// ScaleOnTheFly::SolveScaleIRLS: minimise sum Cauchy_k( w (G*coeff - Iobs) ) over G >= 0.
double SolveScaleIRLS(const std::vector<double> &coeff, const std::vector<double> &Iobs,
const std::vector<double> &weight, double robust_k) {
auto weighted_scale = [&](auto robust_weight) {
double num = 0.0, den = 0.0;
for (size_t i = 0; i < coeff.size(); ++i) {
const double rw = robust_weight(i);
const double w2 = weight[i] * weight[i];
num += rw * w2 * coeff[i] * Iobs[i];
den += rw * w2 * coeff[i] * coeff[i];
}
return den > 0.0 ? num / den : NAN;
};
double G = weighted_scale([](size_t) { return 1.0; });
if (!std::isfinite(G))
return 1.0;
G = std::max(0.0, G);
const double k2 = robust_k * robust_k;
for (int iter = 0; iter < 30; ++iter) {
const double G_prev = G;
const double G_next = weighted_scale([&](size_t i) {
const double res = weight[i] * (G * coeff[i] - Iobs[i]);
return 1.0 / (1.0 + res * res / k2);
});
if (!std::isfinite(G_next))
break;
G = std::max(0.0, G_next);
if (std::abs(G - G_prev) <= 1e-7 * std::max(G, 1.0))
break;
}
return G;
}
// The rotation by the angle-axis vector (psi_x, psi_y, 0) as a matrix (Rodrigues), so that one tilt
// is applied to all the reflections of a crystal by a matrix product each.
std::array<double, 9> TiltMatrix(double psi_x, double psi_y) {
const double theta = std::sqrt(psi_x * psi_x + psi_y * psi_y);
if (theta < 1e-15)
return {1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0};
const double kx = psi_x / theta, ky = psi_y / theta;
const double c = std::cos(theta), s = std::sin(theta), t = 1.0 - c;
return {c + t * kx * kx, t * kx * ky, s * ky,
t * kx * ky, c + t * ky * ky, -s * kx,
-s * ky, s * kx, c};
}
// ComputeP with the tilt given as its rotation matrix.
struct TiltModel {
double s0x, s0y, s0z, inv_lambda;
double gamma0, gamma_e, bw;
double P(const std::array<double, 9> &R, const FitObs &o) const {
const double qx = R[0] * o.qx + R[1] * o.qy + R[2] * o.qz;
const double qy = R[3] * o.qx + R[4] * o.qy + R[5] * o.qz;
const double qz = R[6] * o.qx + R[7] * o.qy + R[8] * o.qz;
const double de = VecLen(qx + s0x, qy + s0y, qz + s0z) - inv_lambda;
const double sig_ang = gamma_e * VecLen(qx, qy, qz);
const double sbw = bw * std::fabs(qz);
const double sig2 = gamma0 * gamma0 + sig_ang * sig_ang + sbw * sbw;
if (!(sig2 > 0.0))
return 1.0;
return std::exp(-0.5 * de * de / sig2);
}
};
// Refine the orientation tilt (psi_x, psi_y) holding the scale G fixed: minimise
// sum_i rho(r_i^2) / 2 + |psi / sigma_prior|^2 / 2, r_i = weight_i (G p_i(psi) Iref_i / corr_i - Iobs_i),
// with the Cauchy rho(s) = k^2 log(1 + s / k^2) - the intensity-space objective of ScaleOnTheFly, and
// the Gaussian prior a proper MAP term since r_i is already in sigma units. Levenberg-Marquardt on the
// normal equations reweighted by rho', the Jacobian by central differences, every trial tilt held inside
// the bound. Returns false when the cost cannot be evaluated, leaving psi as it came in.
bool RefineTilt(const std::vector<FitObs> &obs, const TiltModel &model, double G, double robust_k,
double inv_sigma_prior, double max_tilt, double psi[2]) {
constexpr int MAX_ITERATIONS = 25;
constexpr double STEP = 1e-7; // rad, for the central differences
const double k2 = robust_k * robust_k;
const double prior2 = inv_sigma_prior * inv_sigma_prior;
auto cost = [&](const double p[2]) {
const auto R = TiltMatrix(p[0], p[1]);
double c = 0.5 * prior2 * (p[0] * p[0] + p[1] * p[1]);
for (const auto &o: obs) {
const double r = o.weight * (G * model.P(R, o) * o.inv_corr * o.Iref - o.Iobs);
c += 0.5 * k2 * std::log1p(r * r / k2);
}
return c;
};
double current = cost(psi);
if (!std::isfinite(current))
return false;
double lambda = 1e-4;
for (int iter = 0; iter < MAX_ITERATIONS; ++iter) {
const auto R = TiltMatrix(psi[0], psi[1]);
const auto Rxp = TiltMatrix(psi[0] + STEP, psi[1]), Rxm = TiltMatrix(psi[0] - STEP, psi[1]);
const auto Ryp = TiltMatrix(psi[0], psi[1] + STEP), Rym = TiltMatrix(psi[0], psi[1] - STEP);
double A00 = prior2, A01 = 0.0, A11 = prior2;
double b0 = prior2 * psi[0], b1 = prior2 * psi[1];
for (const auto &o: obs) {
const double a = o.weight * G * o.inv_corr * o.Iref;
const double r = a * model.P(R, o) - o.weight * o.Iobs;
const double jx = a * (model.P(Rxp, o) - model.P(Rxm, o)) / (2.0 * STEP);
const double jy = a * (model.P(Ryp, o) - model.P(Rym, o)) / (2.0 * STEP);
const double w = 1.0 / (1.0 + r * r / k2); // rho'
A00 += w * jx * jx;
A01 += w * jx * jy;
A11 += w * jy * jy;
b0 += w * jx * r;
b1 += w * jy * r;
}
bool accepted = false;
double trial[2] = {psi[0], psi[1]};
double trial_cost = current;
while (lambda < 1e10) {
const double M00 = A00 * (1.0 + lambda), M11 = A11 * (1.0 + lambda);
const double det = M00 * M11 - A01 * A01;
if (!(det > 0.0))
break;
trial[0] = std::clamp(psi[0] - (M11 * b0 - A01 * b1) / det, -max_tilt, max_tilt);
trial[1] = std::clamp(psi[1] - (M00 * b1 - A01 * b0) / det, -max_tilt, max_tilt);
trial_cost = cost(trial);
if (std::isfinite(trial_cost) && trial_cost < current) {
accepted = true;
lambda = std::max(lambda / 10.0, 1e-12);
break;
}
lambda *= 10.0;
}
if (!accepted)
break;
const double step = std::hypot(trial[0] - psi[0], trial[1] - psi[1]);
const double decrease = current - trial_cost;
psi[0] = trial[0];
psi[1] = trial[1];
current = trial_cost;
if (decrease <= 1e-6 * current || step <= 1e-10)
break;
}
return true;
}
}
StillsPartialityRefine::StillsPartialityRefine(const DiffractionExperiment &x)
: experiment_(x),
hkl_key_generator_(x.GetScalingSettings().GetMergeFriedel(), x.GetSpaceGroupOrP1()),
d_min_limit_(x.GetScalingSettings().GetHighResolutionLimit_A()),
d_max_limit_(x.GetScalingSettings().GetLowResolutionLimit_A()),
min_partiality_(x.GetScalingSettings().GetMinPartiality()),
bandwidth_sigma_(x.GetBandwidthFWHM().value_or(0.0f) / 2.3548f) {}
double StillsPartialityRefine::RefineOne(IntegrationOutcome &outcome,
const std::map<HKLKey, double> &reference,
const std::optional<RunWidth> &run_width) const {
if (outcome.reflections.empty())
return 0.0;
const Coord Astar = outcome.latt.Astar();
const Coord Bstar = outcome.latt.Bstar();
const Coord Cstar = outcome.latt.Cstar();
const Coord S0 = outcome.geom.GetScatteringVector();
const double inv_lambda = 1.0 / outcome.geom.GetWavelength_A();
auto base_q = [&](const Reflection &r) {
return Astar * static_cast<float>(r.h) + Bstar * static_cast<float>(r.k)
+ Cstar * static_cast<float>(r.l);
};
// Collect the reflections that constrain the fit (accepted, non-ice, finite, present in the reference).
std::vector<FitObs> obs;
obs.reserve(outcome.reflections.size());
// Moments of the excitation error against resolution: de^2 ~ gamma0^2 + gamma_e^2 * d*^2, fitted per
// crystal by ordinary least squares on (d*^2, de^2). Both components come out of the data.
double m_n = 0.0, m_x = 0.0, m_xx = 0.0, m_y = 0.0, m_xy = 0.0;
size_t n_de = 0;
for (const Reflection &r: outcome.reflections) {
if (r.on_ice_ring || !AcceptReflection(r, d_min_limit_, d_max_limit_))
continue;
if (!std::isfinite(r.I) || !std::isfinite(r.sigma) || r.sigma <= 0.0f)
continue;
const auto it = reference.find(hkl_key_generator_(r));
if (it == reference.end() || !std::isfinite(it->second))
continue;
const Coord q = base_q(r);
obs.push_back(FitObs{
.qx = q.x, .qy = q.y, .qz = q.z,
.Iref = it->second,
.Iobs = static_cast<double>(r.I),
.inv_corr = SafeInv(r.prescaling_corr * r.qe_corr * r.flight_corr, 1.0),
.weight = SafeInv(r.sigma, 1.0),
});
// Excitation error at the stored orientation (psi = 0), collected as the moments of de^2 against
// d*^2, so BOTH width components are fitted rather than one being forced to zero. Forcing the
// width to be purely angular (gamma0 = 0) pins it to the high-resolution edge - it is fitted over
// a d*^2-dense population - and it then collapses at low d*, giving p ~ 0 for reflections that
// were plainly recorded, which inflated the merged low-resolution intensity scale ~3.6x.
const double dstar = VecLen(q.x, q.y, q.z);
const double de0 = VecLen(q.x + S0.x, q.y + S0.y, q.z + S0.z) - inv_lambda;
if (dstar > 1e-9) {
const double x = dstar * dstar, y = de0 * de0;
m_n += 1.0;
m_x += x;
m_xx += x * x;
m_y += y;
m_xy += x * y;
++n_de;
}
}
if (obs.size() < MIN_FIT_REFLECTIONS || n_de == 0)
return 0.0;
// Without the run's measured width (too few reflections in the run to measure it), the width comes
// from this crystal's own reflections. Solve the 2x2 normal equations for de^2 = A + B d*^2. A degenerate spread in d* (all reflections in
// one shell) leaves B undetermined, so fall back to the pure angular width there; a negative fitted
// component is unphysical and is clamped to zero, which reduces to the previous model.
//
// Measured outcome, worth knowing before touching this: the fit does NOT split the width between the
// two terms - it returns gamma0 ~ 4e-4 1/A and gamma_e ~ 0 (their cross-over sits at d = 0.3 A, far
// outside any measured range), i.e. a width constant in the LINEAR Ewald distance. That is
// structural, not a fluke: prediction accepts reflections on a fixed linear |dist_ewald| cutoff, so
// the accepted population's de^2 is flat in d*^2 by construction and the slope is genuinely ~0. The
// truncated population cannot constrain an angular term, and its width is the window's, not the
// crystal's - which is why the run's measured width is used wherever there is one.
const double det = m_n * m_xx - m_x * m_x;
double A = 0.0, B = 0.0;
if (std::fabs(det) > 1e-30) {
A = (m_xx * m_y - m_x * m_xy) / det;
B = (m_n * m_xy - m_x * m_y) / det;
} else {
B = m_x > 0.0 ? m_y / m_x : 0.0;
}
double gamma0 = std::sqrt(std::max(0.0, A));
const double gamma_e_fit = std::max(std::sqrt(std::max(0.0, B)), 1e-9);
double gamma_e = settings_.gamma_e > 0.0 ? settings_.gamma_e : gamma_e_fit;
double bw = bandwidth_sigma_;
if (run_width) {
gamma0 = run_width->gamma0;
gamma_e = std::max(run_width->gamma_e, 1e-9);
bw = run_width->bandwidth_sigma;
}
double psi[2] = {0.0, 0.0};
double G = 1.0;
const TiltModel model{.s0x = S0.x, .s0y = S0.y, .s0z = S0.z, .inv_lambda = inv_lambda,
.gamma0 = gamma0, .gamma_e = gamma_e, .bw = bw};
const bool refine_tilt = obs.size() >= settings_.min_reflections;
const int inner = refine_tilt ? settings_.inner_iterations : 1;
for (int it = 0; it < inner; ++it) {
// (1) Solve G given the current partialities.
std::vector<double> coeff(obs.size()), Iobs(obs.size()), weight(obs.size());
for (size_t j = 0; j < obs.size(); ++j) {
const double p = ComputeP(obs[j].qx, obs[j].qy, obs[j].qz, psi[0], psi[1],
S0.x, S0.y, S0.z, inv_lambda, gamma0, gamma_e, bw);
coeff[j] = p * obs[j].inv_corr * obs[j].Iref;
Iobs[j] = obs[j].Iobs;
weight[j] = obs[j].weight;
}
G = SolveScaleIRLS(coeff, Iobs, weight, settings_.robust_k);
if (!(G > 0.0) || !std::isfinite(G))
return 0.0;
if (!refine_tilt)
break;
// (2) Refine the tilt holding G fixed. A cost that cannot be evaluated keeps the tilt this crystal
// came in with and stops refining it - G alone is still a usable model.
const double inv_sigma_prior = settings_.prior_sigma_deg > 0.0 ? kRadToDeg / settings_.prior_sigma_deg : 0.0;
if (!RefineTilt(obs, model, G, settings_.robust_k, inv_sigma_prior, settings_.max_tilt_rad, psi))
break;
}
// Keep what the crystal came in with. This refinement is on by default, so a crystal the tilt model
// happens to suit WORSE than the fixed partiality it replaces must not be made worse by it - and
// whether it suits is only known once the corrections are written and the CC re-measured.
const auto cc_before = outcome.image_scale_cc;
const auto g_before = outcome.image_scale_g;
std::vector<std::pair<float, float>> before; // partiality, image_scale_corr
before.reserve(outcome.reflections.size());
for (const auto &r: outcome.reflections)
before.emplace_back(r.partiality, r.image_scale_corr);
// Write the refined partiality + scale correction onto every reflection of the crystal (not only the
// fit subset), so the merge sees a consistent model. image_scale_corr = prescaling_corr * qe_corr * flight_corr /
// (partiality * G), the same composition ScaleOnTheFly writes.
for (auto &r: outcome.reflections) {
const Coord q = base_q(r);
const double p = ComputeP(q.x, q.y, q.z, psi[0], psi[1], S0.x, S0.y, S0.z, inv_lambda,
gamma0, gamma_e, bw);
r.partiality = static_cast<float>(p);
const float corr = r.prescaling_corr * r.qe_corr * r.flight_corr;
const double denom = p * G;
r.image_scale_corr = (std::isfinite(corr) && std::isfinite(denom) && denom > 0.0)
? static_cast<float>(corr / denom)
: NAN;
}
outcome.image_scale_g = static_cast<float>(G);
// The corrections just changed, so the CC that ScaleOnTheFly measured no longer describes them.
// Refresh it here: it is reported per image and --min-image-cc drops images by it, so it has to be
// the CC of the data that is actually merged.
const auto [cc, cc_n] = ImageReferenceCC(outcome.reflections, reference, hkl_key_generator_,
d_min_limit_, d_max_limit_, min_partiality_);
// Adopt the refined model only if it correlates with the reference at least as well as the model it
// replaces. Rejecting puts the crystal back exactly as it arrived, which is the same state a
// crystal with too few reflections to fit ends in. A CC that cannot be measured at all counts as
// worse, not as no opinion: ImageReferenceCC returns NaN when too few reflections clear the
// partiality cut, which is precisely what a refinement that collapsed the partialities produces -
// and adopting it would leave image_scale_cc NaN, on which --min-image-cc drops the image outright.
if (cc_before.has_value() && std::isfinite(*cc_before) && !(std::isfinite(cc) && cc >= *cc_before)) {
for (size_t i = 0; i < outcome.reflections.size(); ++i) {
outcome.reflections[i].partiality = before[i].first;
outcome.reflections[i].image_scale_corr = before[i].second;
}
outcome.image_scale_g = g_before;
return 0.0; // nothing adopted, so no tilt to report
}
outcome.image_scale_cc = cc;
outcome.image_scale_cc_n = cc_n;
const double tilt_deg = std::sqrt(psi[0] * psi[0] + psi[1] * psi[1]) * kRadToDeg;
return tilt_deg;
}
std::optional<StillsPartialityRefine::RunWidth> StillsPartialityRefine::MeasureRunWidth(
const std::vector<IntegrationOutcome> &outcomes, const std::optional<UnitCell> &reference_cell) const {
// The rocking width measured on the crystals rather than on the prediction window. A lattice point
// sits anywhere across the window with equal likelihood, while what it records is I_full * p(de), so
// the intensity-weighted second moment of the excitation error, sum I de^2 / sum I, is the width s^2
// of a Gaussian p - corrected for the window cutting the curve's tails (UntruncatedVariance). The
// plain moment of de over the predicted reflections, which the per-crystal fit in RefineOne uses, is
// instead the window's own (W^2 / 3). Measured in shells of d*^2 over the whole run, where the
// intensities of thousands of crystals average out, and fitted as s^2 = gamma0^2 + gamma_e^2 d*^2 +
// (bandwidth_sigma lambda d*^2 / 2)^2.
const auto &indexing = experiment_.GetIndexingSettings();
struct Point { double x, de2, w, var_w; };
std::vector<Point> pts;
for (const auto &o: outcomes) {
if (!o.image_scale_g || !(*o.image_scale_g > 0.0))
continue;
if (reference_cell && !o.latt.GetUnitCell().is_close(*reference_cell, indexing.GetUnitCellDistTolerance(),
indexing.GetUnitCellAngleTolerance_deg()))
continue;
for (const auto &r: o.reflections) {
if (r.on_ice_ring || !AcceptReflection(r, d_min_limit_, d_max_limit_))
continue;
const double corr = r.prescaling_corr * r.qe_corr * r.flight_corr / *o.image_scale_g;
const double w = r.I * corr, sigma_w = r.sigma * corr;
if (!std::isfinite(w) || !std::isfinite(sigma_w) || !std::isfinite(r.dist_ewald) || !(r.d > 0.0f))
continue;
pts.push_back({1.0 / (static_cast<double>(r.d) * r.d),
static_cast<double>(r.dist_ewald) * r.dist_ewald, w, sigma_w * sigma_w});
}
}
constexpr size_t N_SHELLS = 8;
if (pts.size() < 100 * N_SHELLS)
return std::nullopt;
std::sort(pts.begin(), pts.end(), [](const Point &a, const Point &b) { return a.x < b.x; });
Logger logger("StillsPartialityRefine");
// A shell's moment is no better than the summed intensity it is weighted by, so a shell is used only
// where that sum is measured to 10 % (sum I / sigma(sum I) >= 10): the shells beyond the diffraction
// limit, where the sum is noise and can even be negative, say nothing about the width.
constexpr double MIN_SHELL_SIGNAL = 10.0;
std::vector<double> sx, sy;
for (size_t k = 0; k < N_SHELLS; ++k) {
double sw = 0.0, svar = 0.0, swde2 = 0.0, sde2 = 0.0, sumx = 0.0;
const size_t lo = k * pts.size() / N_SHELLS, hi = (k + 1) * pts.size() / N_SHELLS;
for (size_t i = lo; i < hi; ++i) {
sw += pts[i].w;
svar += pts[i].var_w;
swde2 += pts[i].w * pts[i].de2;
sde2 += pts[i].de2;
sumx += pts[i].x;
}
const double n = static_cast<double>(hi - lo);
if (!(sw >= MIN_SHELL_SIGNAL * std::sqrt(svar)) || !(swde2 > 0.0))
continue;
const double x = sumx / n, y = UntruncatedVariance(swde2 / sw, sde2 / n);
sx.push_back(x);
sy.push_back(y);
logger.Debug("Stills rocking width at d = {:.2f} A: {:.2e} 1/A ({:.3f} deg), I/sigma {:.0f}", 1.0 / std::sqrt(x),
std::sqrt(y), std::sqrt(y / x) * kRadToDeg, sw / std::sqrt(svar));
}
if (sx.size() < 3)
return std::nullopt;
// Least squares for s^2 = A + B d*^2 + C d*^4 over the shells. Every term is a variance, so a negative
// one is unphysical: of the fits on each subset of the three terms, the best with none negative is kept.
std::array<double, 3> best{};
double best_residual = INFINITY;
for (int mask = 1; mask < 8; ++mask) {
std::vector<int> terms;
for (int t = 0; t < 3; ++t)
if (mask & (1 << t))
terms.push_back(t);
const int m = static_cast<int>(terms.size());
Eigen::MatrixXd M = Eigen::MatrixXd::Zero(m, m);
Eigen::VectorXd v = Eigen::VectorXd::Zero(m);
for (size_t k = 0; k < sx.size(); ++k)
for (int i = 0; i < m; ++i) {
const double fi = std::pow(sx[k], terms[i]);
v(i) += fi * sy[k];
for (int j = 0; j < m; ++j)
M(i, j) += fi * std::pow(sx[k], terms[j]);
}
const Eigen::VectorXd c = M.ldlt().solve(v);
if (!c.allFinite() || (c.array() < 0.0).any())
continue;
std::array<double, 3> coef{};
for (int i = 0; i < m; ++i)
coef[terms[i]] = c(i);
double residual = 0.0;
for (size_t k = 0; k < sx.size(); ++k) {
const double r = sy[k] - coef[0] - coef[1] * sx[k] - coef[2] * sx[k] * sx[k];
residual += r * r;
}
if (residual < best_residual) {
best_residual = residual;
best = coef;
}
}
if (!std::isfinite(best_residual) || !(best[0] + best[1] + best[2] > 0.0))
return std::nullopt;
// The d*^4 term is a bandwidth: its radial smear bw |q_z|, with |q_z| = lambda d*^2 / 2 on the sphere.
const RunWidth width{.gamma0 = std::sqrt(best[0]), .gamma_e = std::sqrt(best[1]),
.bandwidth_sigma = 2.0 * std::sqrt(best[2]) / experiment_.GetWavelength_A()};
logger.Info("Stills rocking width measured: {:.2e} 1/A + {:.3f} deg angular + {:.4f} bandwidth (FWHM)",
width.gamma0, width.gamma_e * kRadToDeg, width.bandwidth_sigma * 2.3548);
return width;
}
double StillsPartialityRefine::Run(std::vector<IntegrationOutcome> &outcomes, size_t nthreads,
const std::optional<UnitCell> &reference_cell) const {
const auto &indexing = experiment_.GetIndexingSettings();
auto merged_crystal = [&](const IntegrationOutcome &o) {
return !reference_cell || o.latt.GetUnitCell().is_close(*reference_cell,
indexing.GetUnitCellDistTolerance(),
indexing.GetUnitCellAngleTolerance_deg());
};
if (nthreads == 0)
nthreads = AvailableCpus();
nthreads = std::max<size_t>(1, nthreads);
double last_mean_tilt = 0.0;
const auto run_width = MeasureRunWidth(outcomes, reference_cell);
for (int outer = 0; outer < settings_.outer_iterations; ++outer) {
// Reference full intensities from the current corrections.
const std::vector<MergedReflection> merged = MergeAll(experiment_, outcomes, nthreads, reference_cell);
std::map<HKLKey, double> reference;
for (const auto &m: merged)
reference[hkl_key_generator_(m)] = m.I;
std::atomic<double> tilt_sum{0.0};
std::atomic<size_t> tilt_n{0};
std::atomic<size_t> next{0};
auto worker = [&]() {
size_t i = next.fetch_add(1);
while (i < outcomes.size()) {
const double t = merged_crystal(outcomes[i]) ? RefineOne(outcomes[i], reference, run_width) : 0.0;
if (t > 0.0) {
double prev = tilt_sum.load();
while (!tilt_sum.compare_exchange_weak(prev, prev + t)) {}
tilt_n.fetch_add(1);
}
i = next.fetch_add(1);
}
};
const size_t nt = std::min(nthreads, std::max<size_t>(1, outcomes.size()));
if (nt <= 1) {
worker();
} else {
std::vector<std::future<void>> futures;
futures.reserve(nt);
for (size_t t = 0; t < nt; ++t)
futures.emplace_back(std::async(std::launch::async, worker));
for (auto &f: futures)
f.get();
}
last_mean_tilt = tilt_n > 0 ? tilt_sum.load() / static_cast<double>(tilt_n.load()) : 0.0;
}
return last_mean_tilt;
}