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Jungfraujoch/image_analysis/scale_merge/StillsPartialityRefine.cpp
T
leonarski_fandClaude Opus 5.5 3c4d730f89 RESULT-CHANGING (owner decision): stills tilt post-refinement solved directly instead of by Ceres
Each crystal's (psi_x, psi_y) tilt was refined by a Ceres problem rebuilt for every inner
iteration: one auto-differentiated residual block and one Cauchy loss per reflection. With the
scaling reference cleaned up it was 70% of the stills scale/merge. The same objective - Cauchy
on the sigma-weighted intensity residuals plus the Gaussian prior on the tilt, the tilt bounded -
is now minimised by a small Levenberg-Marquardt on the rho'-reweighted 2x2 normal equations,
the tilt applied to all reflections through one rotation matrix and the Jacobian taken by
central differences.

It reaches the same answer to optimizer precision: on the new synthetic test
(StillsPartialityRefine_RecoversTheTilt) partiality error 0.0559 -> 0.03019 with Ceres and
0.03016 with this, mean tilt 0.02065 vs 0.02067 deg; on two 25k-frame XFEL runs (--mode scale)
CC1/2, I/sigma, R_pim and the CC against a deposited lysozyme model agree to 0.0005, mean
|dpsi| 0.023 deg on both. Scale+merge 6.9 -> 3.0 s (--mode scale, loaded box).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
2026-10-14 11:59:09 +02:00

449 lines
21 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 <ceres/rotation.h>
#include "Merge.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);
}
// 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 {
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();
const double bw = bandwidth_sigma_;
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;
// 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; the resolution-independent one is what the
// data actually support.
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;
}
const 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);
const double gamma_e = settings_.gamma_e > 0.0 ? settings_.gamma_e : gamma_e_fit;
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;
}
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;
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) : 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;
}