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Jungfraujoch/image_analysis/geom_refinement/PostRefine.cpp
T
jungfrauandClaude Opus 5 e11c2a2b20 Fit the goniometer rotation scale in closed form
The fit has ONE parameter, and it was handed to Ceres as one residual block
per rocking event - 8 million of them on a large crystal. Each block is a
functor, an auto-diff cost function and a loss object on the heap, and the
solver then factorises an 8-million-by-one Jacobian on every iteration. It cost
13.7 s.

The residual is closed-form in k. A rotation preserves length, so |p_lab| is
|e_mid| whatever k is and only the z component moves; Rodrigues gives it
exactly:

  r(k) = C + A cos(a k) - B sin(a k) = C + R cos(a k + psi)
  C = lambda |e|^2 / 2 + u_z (u.e),  A = e_z - u_z (u.e),  B = (u x e)_z

with a the event's angle from the sweep centre. That is the same function the
functor computes - Ceres uses the exact Rodrigues form here, so there is no
small-angle branch to disagree with - and it reduces the fit to minimising a
smooth function of one variable over the interval the solver was bounded to.
It is scanned on a grid and then closed in by golden section; the objective's
curvature jumps wherever an event crosses the Huber knee, which is why this is
not a Newton iteration.

The coefficients are computed in double and stored narrowed. Their rounding
moves the minimiser by ~1e-10, and k is carried downstream as a float, so the
committed value is the same to far more digits than anything reads.

One pass over the events yields the five per-fifth partial sums, so the
all-data fit and the five leave-a-fifth-out folds share it. That matters
because the jackknife only runs when the fit is big enough to act on, and on a
crystal that trips it the old code paid for six full solves.

The partials gather ahead of it counted first and then filled instead of
growing one vector by push_back tens of millions of times, which copied the
whole thing on every doubling.

Measured: unchanged verdict and k to five decimals on the regression crystals.
Full 24-crystal battery: same space group on all 24, none failed, 15m32s ->
13m35s together with the scale/merge changes.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-08-15 18:56:09 -04:00

579 lines
36 KiB
C++

// SPDX-FileCopyrightText: 2026 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only
#include "../../common/ParallelFor.h"
#include "PostRefine.h"
#include <algorithm>
#include <array>
#include <cmath>
#include <mutex>
#include "../../common/JFJochMath.h" // PI
#include "XtalResidual.h" // XtalResidual (the positional detector<->reciprocal residual, step B)
#include "LatticeReduction.h"
#include "ceres/ceres.h"
#include "ceres/rotation.h"
namespace {
// One integrated partial, flattened across all images.
struct Partial {
int h, k, l;
float img;
double I, sigma;
double angle_rad; // frame mid-exposure goniometer angle
double obs_x, obs_y; // observed spot centroid (pixels); NAN if the box sum found no centroid
};
// A rocking event and its precomputed reference reciprocal vector (phi=0 frame, from the indexed lattice).
struct Event {
double phi_obs; // rad, intensity-weighted rocking centroid
double weight; // sqrt(sum I / sum sigma)
double e_ref[3]; // h*a* + k*b* + l*c* at the reference (unrefined) cell/orientation
int h, k, l;
};
// Distance-INDEPENDENT Ewald excitation residual for a uniform cell-scale parameter s and a refined
// goniometer axis (3-vector). The header-distance miscalibration leaves a uniform cell scale; the axis is
// the other phi_obs lever. Both are phi_obs-constrained (distance-independent). e_ref is the reference
// reciprocal (h*a* + k*b* + l*c* at the indexed cell). On the Ewald sphere <=> |p|^2 + 2 p_z/lambda == 0.
struct ScaleAxisExcitationResidual {
ScaleAxisExcitationResidual(double lambda, double angle_rad, double weight, const double e_ref[3])
: inv_lambda(1.0 / lambda), angle_rad(angle_rad), weight(weight),
ex(e_ref[0]), ey(e_ref[1]), ez(e_ref[2]) {}
template<typename T>
bool operator()(const T *const s, const T *const axis, T *residual) const {
const T inv_s = T(1) / s[0];
const T p_ref[3] = {T(ex) * inv_s, T(ey) * inv_s, T(ez) * inv_s};
const T aa[3] = {T(-angle_rad) * axis[0], T(-angle_rad) * axis[1], T(-angle_rad) * axis[2]};
T p_lab[3];
ceres::AngleAxisRotatePoint(aa, p_ref, p_lab);
const T zeta = p_lab[0] * p_lab[0] + p_lab[1] * p_lab[1] + p_lab[2] * p_lab[2]
+ T(2.0) * p_lab[2] * T(inv_lambda);
residual[0] = T(weight) * zeta * T(0.5) / T(inv_lambda);
return true;
}
const double inv_lambda, angle_rad, weight, ex, ey, ez;
};
// GONIOMETER ROTATION SCALE k: the same Ewald excitation residual, but with the cell scale and the axis
// DIRECTION already committed by step A, so the single free quantity is how far the stage actually turned
// per unit of commanded angle. Two differences from step A matter:
// * the angle is measured from the CENTRE of the sweep, not from the goniometer's zero. The reference
// orientation is the one rotation indexing fitted against the commanded angles, so it has already
// absorbed the MEAN angle error; only the part that varies across the sweep is left to fit. Scaling the
// absolute angle instead - which is what reading k off the length of step A's axis vector does - asks
// the fit to also produce a constant offset it has no parameter for, and the least-squares compromise
// shrinks k towards 1 by var(phi) / (var(phi) + phi_centre^2): exactly a factor of four for the common
// case of a sweep starting at zero.
// * e_mid is the reference reciprocal vector already turned to the sweep centre and divided by the
// committed cell scale, so nothing but k is free.
struct RotationScaleResidual {
RotationScaleResidual(double lambda, double dangle_rad, const double u[3], const double e_mid[3])
: inv_lambda(1.0 / lambda), dangle_rad(dangle_rad),
ux(u[0]), uy(u[1]), uz(u[2]), ex(e_mid[0]), ey(e_mid[1]), ez(e_mid[2]) {}
template<typename T>
bool operator()(const T *const k, T *residual) const {
const T a = T(-dangle_rad) * k[0];
const T aa[3] = {a * T(ux), a * T(uy), a * T(uz)};
const T p_ref[3] = {T(ex), T(ey), T(ez)};
T p_lab[3];
ceres::AngleAxisRotatePoint(aa, p_ref, p_lab);
const T zeta = p_lab[0] * p_lab[0] + p_lab[1] * p_lab[1] + p_lab[2] * p_lab[2]
+ T(2.0) * p_lab[2] * T(inv_lambda);
residual[0] = zeta * T(0.5) / T(inv_lambda);
return true;
}
const double inv_lambda, dangle_rad, ux, uy, uz, ex, ey, ez;
};
} // namespace
PostRefineResult PostRefineRotationGeometry(const std::vector<IntegrationOutcome> &outcomes,
const GoniometerAxis &axis,
const DiffractionGeometry &nominal_geom,
const CrystalLattice &reference_latt,
const PostRefineSettings &settings,
Logger &logger) {
PostRefineResult result;
result.geom = nominal_geom;
result.cell = reference_latt.GetUnitCell();
result.distance_before_mm = nominal_geom.GetDetectorDistance_mm();
result.distance_after_mm = nominal_geom.GetDetectorDistance_mm();
try {
const double wedge_half = axis.GetWedge_deg() / 2.0;
const double lambda = nominal_geom.GetWavelength_A();
const Coord ax = axis.GetAxis();
const Coord Astar = reference_latt.Astar(), Bstar = reference_latt.Bstar(), Cstar = reference_latt.Cstar();
// Count first, then fill. Growing one vector by push_back over tens of millions of
// reflections copies the whole thing every time it doubles - several gigabytes of pure
// copying - and the counts are cheap to take. Each outcome then owns a slice, so the fill
// runs on all threads and lands in the order the serial loop produced.
const size_t nthreads = std::max(1, settings.num_threads);
const int n_out = static_cast<int>(outcomes.size());
std::vector<size_t> pts_offset(n_out + 1, 0);
ParallelChunks(n_out, nthreads, [&](int lo, int hi) {
for (int o = lo; o < hi; o++) {
size_t keep = 0;
for (const auto &r : outcomes[o].reflections)
if (std::isfinite(r.I) && std::isfinite(r.sigma) && r.sigma > 0.0f)
keep++;
pts_offset[o + 1] = keep;
}
});
for (int o = 0; o < n_out; o++)
pts_offset[o + 1] += pts_offset[o];
std::vector<Partial> pts(pts_offset[n_out]);
ParallelChunks(n_out, nthreads, [&](int lo, int hi) {
for (int o = lo; o < hi; o++) {
size_t at = pts_offset[o];
for (const auto &r : outcomes[o].reflections) {
if (!std::isfinite(r.I) || !std::isfinite(r.sigma) || r.sigma <= 0.0f) continue;
const double mid_deg = axis.GetAngle_deg(r.image_number) + wedge_half;
const double ox = std::isfinite(r.observed_x) ? r.observed_x : NAN;
const double oy = std::isfinite(r.observed_y) ? r.observed_y : NAN;
pts[at++] = Partial{r.h, r.k, r.l, r.image_number, r.I, r.sigma,
mid_deg * PI / 180.0, ox, oy};
}
}
});
logger.Info("Post-refine: {} partials gathered", pts.size());
if (pts.size() < static_cast<size_t>(settings.min_events)) return result;
std::sort(pts.begin(), pts.end(), [](const Partial &a, const Partial &b) {
if (a.h != b.h) return a.h < b.h;
if (a.k != b.k) return a.k < b.k;
if (a.l != b.l) return a.l < b.l;
return a.img < b.img;
});
// Split into rocking events (same raw hkl, adjacent frames). Only >=2-frame events carry an
// unbiased phi_obs (a single-frame centroid is just the frame centre); precompute e_ref per event.
constexpr float MAX_FRAME_GAP = 2.0f;
std::vector<Event> events;
size_t i = 0, event_frames = 0;
while (i < pts.size()) {
size_t j = i + 1;
while (j < pts.size() && pts[j].h == pts[i].h && pts[j].k == pts[i].k && pts[j].l == pts[i].l
&& pts[j].img - pts[j - 1].img <= MAX_FRAME_GAP)
++j;
if (j - i >= 2) {
double sumI = 0, sumIphi = 0, sumSig = 0;
for (size_t m = i; m < j; ++m) {
const double Ipos = std::max(0.0, pts[m].I);
sumI += Ipos; sumIphi += Ipos * pts[m].angle_rad; sumSig += pts[m].sigma;
}
if (sumI > 0.0 && sumSig > 0.0) {
const double phi = sumIphi / sumI;
event_frames += j - i;
const Coord e = Astar * static_cast<float>(pts[i].h) + Bstar * static_cast<float>(pts[i].k)
+ Cstar * static_cast<float>(pts[i].l);
events.push_back(Event{phi, std::sqrt(sumI / sumSig), {e.x, e.y, e.z},
pts[i].h, pts[i].k, pts[i].l});
}
}
i = j;
}
// Frames per event is the phi_obs sampling: near 2 the reflections barely rock, so the angle
// this refinement is fitted to is under-determined. It is a geometry count, so unlike an
// intensity-weighted width it cannot be inflated by noise.
logger.Info("Post-refine: {} multi-frame rocking events ({:.1f} frames per event)", events.size(),
events.empty() ? 0.0 : static_cast<double>(event_frames) / events.size());
if (static_cast<int>(events.size()) < settings.min_events) return result;
// The rotation-scale fit further down is a single scalar whose whole point is how the residual
// varies ALONG the sweep, so it keeps every event. The cap below ranks by I/sigma, and on the
// crystals that have a stage fault the strong events sit in the middle of the sweep - the part
// that still indexes - so a capped set would leave the ends unrepresented in exactly the fit that
// has to see them.
const std::vector<Event> scale_events = events;
constexpr size_t MAX_EVENTS = 20000;
if (events.size() > MAX_EVENTS) {
std::nth_element(events.begin(), events.begin() + MAX_EVENTS, events.end(),
[](const Event &a, const Event &b) { return a.weight > b.weight; });
events.resize(MAX_EVENTS);
}
// ---- GEOMETRY REFINEMENT: the XtalOptimizer-equivalent, done as TWO SEPARATE
// cross-validated steps rather than one joint fit (the same lesson as integration: refining the
// profile width and the scale jointly fails, refining them separately works). Each step is committed
// only if it lowers a HELD-OUT (deterministic split-half) residual - otherwise that part of the
// geometry is left at nominal ("quit when things go wrong"):
// Step A: cell scale + rotation axis from phi_obs (distance-independent excitation residual).
// Step B: detector distance + beam centre from the observed spot positions, with the cell FIXED at
// step A (so the positional residual is no longer degenerate with the cell scale).
// Detector tilt is held fixed (gauge-coupled to orientation on a single crystal). ----
if (settings.refine_geometry) {
const gemmi::CrystalSystem sys =
(settings.crystal_system == gemmi::CrystalSystem::Trigonal) ? gemmi::CrystalSystem::Hexagonal
: settings.crystal_system;
const double ax0[3] = {ax.x, ax.y, ax.z};
const double lambda_l = lambda;
const double rot3 = nominal_geom.GetPoniRot3_rad();
const double pixel_mm = nominal_geom.GetPixelSize_mm();
const double det_rot[2] = {nominal_geom.GetPoniRot1_rad(), nominal_geom.GetPoniRot2_rad()};
const UnitCell r0 = reference_latt.GetUnitCell();
// Deterministic split of the reflections into a fit half and a held-out half. Avalanche-mix the
// hkl hash so the split bit is decorrelated from the LSB - a plain h+k+l parity collides with the
// lattice centering condition (e.g. an I-centred lattice has h+k+l even for EVERY present
// reflection, so a parity split would leave the validation half empty).
auto is_val = [](int h, int k, int l) {
unsigned u = static_cast<unsigned>(h) * 2654435761u + static_cast<unsigned>(k) * 2246822519u
+ static_cast<unsigned>(l) * 3266489917u;
u ^= u >> 15; u *= 2246822519u; u ^= u >> 13;
return (u & 1u) != 0u;
};
enum Subset { FIT, VAL, ALL };
auto in = [&](int h, int k, int l, Subset s) {
return s == ALL || (is_val(h, k, l) == (s == VAL)); };
// ===== Step A: cell scale s + rotation axis from phi_obs =====
auto excit_cost = [&](Subset s, double sc, const double axv[3]) {
double c = 0.0; int n = 0;
for (const auto &ev : events) {
if (!in(ev.h, ev.k, ev.l, s)) continue;
ScaleAxisExcitationResidual r(lambda_l, ev.phi_obs, 1.0, ev.e_ref);
double sd = sc, av[3] = {axv[0], axv[1], axv[2]}, resid = 0.0;
r(&sd, av, &resid); c += resid * resid; ++n;
}
return n ? c / n : 0.0;
};
auto solve_scale_axis = [&](Subset s, double &s_out, double ax_out[3]) {
double sc = 1.0, axv[3] = {ax0[0], ax0[1], ax0[2]};
ceres::Problem p;
for (const auto &ev : events) {
if (!in(ev.h, ev.k, ev.l, s)) continue;
p.AddResidualBlock(new ceres::AutoDiffCostFunction<ScaleAxisExcitationResidual, 1, 1, 3>(
new ScaleAxisExcitationResidual(lambda_l, ev.phi_obs, settings.excitation_weight, ev.e_ref)),
new ceres::CauchyLoss(0.02), &sc, axv);
}
p.SetParameterLowerBound(&sc, 0, 0.9); p.SetParameterUpperBound(&sc, 0, 1.1);
for (int j = 0; j < 3; ++j) { p.SetParameterLowerBound(axv, j, ax0[j] - 0.05);
p.SetParameterUpperBound(axv, j, ax0[j] + 0.05); }
ceres::Solver::Options o; o.linear_solver_type = ceres::DENSE_QR; o.max_num_iterations = 50;
o.num_threads = std::max(1, settings.num_threads); o.logging_type = ceres::LoggingType::SILENT;
ceres::Solver::Summary sum; ceres::Solve(o, &p, &sum);
s_out = sc; ax_out[0] = axv[0]; ax_out[1] = axv[1]; ax_out[2] = axv[2];
return sum.IsSolutionUsable();
};
double s_fit = 1.0, ax_fit[3];
const bool convA = solve_scale_axis(FIT, s_fit, ax_fit);
const double cvA_nom = excit_cost(VAL, 1.0, ax0);
const double cvA_ref = excit_cost(VAL, s_fit, ax_fit);
// Commit the cell scale only for a small, credible move: a well-calibrated header needs < ~0.6 %,
// so a > 1 % scale is a red flag (on multi-lattice / noisy data the excitation fit is biased the
// same way in every cross-validation fold, so the relative-improvement gate cannot catch it).
result.cell_refined = convA && cvA_ref < 0.98 * cvA_nom && std::fabs(s_fit - 1.0) < 0.01;
double s = 1.0, axv[3] = {ax0[0], ax0[1], ax0[2]};
if (result.cell_refined) solve_scale_axis(ALL, s, axv); // commit: re-fit on all data
const double axlen = std::sqrt(axv[0]*axv[0] + axv[1]*axv[1] + axv[2]*axv[2]);
const double axdev = std::acos(std::clamp((axv[0]*ax0[0]+axv[1]*ax0[1]+axv[2]*ax0[2])
/ std::max(1e-9, axlen), -1.0, 1.0)) * 180.0 / PI;
logger.Info("Post-refine GEOM step A (cell/axis): s = {:.5f}, rot-axis {:.3f} deg, held-out excit "
"{:.3e} -> {:.3e} => {}", s, axdev, cvA_nom, cvA_ref,
result.cell_refined ? "COMMIT" : "reject (kept nominal cell)");
// ===== Goniometer rotation SCALE k, its own one-parameter fit on the same rocking events =====
// The angles stored in the file are the COMMANDED ones, so a stage that turned k times as far
// is invisible in the header. Nothing else here can represent it: the cell scale, the axis
// direction, the distance and the beam are all orthogonal to a rotation MAGNITUDE error. Fitted
// after step A so the cell scale and the axis direction are fixed at their committed values and
// k is the only free quantity.
const double u[3] = {axv[0] / axlen, axv[1] / axlen, axv[2] / axlen};
double phi_c = 0.0, phi_lo = scale_events[0].phi_obs, phi_hi = scale_events[0].phi_obs;
for (const auto &ev : scale_events) {
phi_c += ev.phi_obs;
phi_lo = std::min(phi_lo, ev.phi_obs);
phi_hi = std::max(phi_hi, ev.phi_obs);
}
phi_c /= static_cast<double>(scale_events.size());
const double sweep_deg = (phi_hi - phi_lo) * 180.0 / PI;
// The reference reciprocal vector turned to the sweep centre, at the committed cell scale. The
// angle then enters the fit measured FROM that centre. A constant crystal missetting about the
// spindle is k with a slope in phi, so measuring the angle from the goniometer's zero instead
// lets a missetting leak into k with gain <phi>/<phi^2> - which depends only on where the sweep
// happens to sit. On a short sweep starting near zero that gain is enormous: a 0.14 deg
// missetting on a 10 deg wedge fakes 1.4 % of k. Referred to the sweep centre the leak is
// identically zero at any width, and no parameter has to be added to get it.
// The residual is closed-form in k, so this is a one-parameter minimisation rather than a
// solver problem. A rotation preserves length, so |p_lab| = |e_mid| whatever k is, and only
// the z component moves; Rodrigues gives it exactly:
//
// r(k) = C + A cos(a k) - B sin(a k) = C + R cos(a k + psi)
// C = lambda |e|^2 / 2 + u_z (u.e), A = e_z - u_z (u.e), B = (u x e)_z, a = phi_obs - phi_c
//
// which is the same function the residual functor computes, to the last bit. Handing 8 million
// one-parameter residual blocks to Ceres instead cost tens of millions of allocations and a
// dense factorisation per iteration, for a fit that a scan over a bounded interval settles.
// Coefficients are computed in double and stored narrowed: their rounding perturbs the
// minimiser by ~1e-10, and k is carried downstream as a float.
struct ScaleTerm { float a, C, R, psi; };
std::vector<ScaleTerm> terms(scale_events.size());
std::vector<int> fifth_of(scale_events.size());
const double aa_c[3] = {-phi_c * u[0], -phi_c * u[1], -phi_c * u[2]};
ParallelChunks(static_cast<int>(scale_events.size()), nthreads, [&](int lo, int hi) {
for (int e = lo; e < hi; ++e) {
const double p[3] = {scale_events[e].e_ref[0] / s, scale_events[e].e_ref[1] / s,
scale_events[e].e_ref[2] / s};
double em[3];
ceres::AngleAxisRotatePoint(aa_c, p, em);
const double ue = u[0] * em[0] + u[1] * em[1] + u[2] * em[2];
const double e2 = em[0] * em[0] + em[1] * em[1] + em[2] * em[2];
const double C = 0.5 * lambda_l * e2 + u[2] * ue;
const double A = em[2] - u[2] * ue;
const double B = u[0] * em[1] - u[1] * em[0];
terms[e] = ScaleTerm{static_cast<float>(scale_events[e].phi_obs - phi_c),
static_cast<float>(C), static_cast<float>(std::hypot(A, B)),
static_cast<float>(std::atan2(B, A))};
fifth_of[e] = std::clamp(static_cast<int>(
5.0 * (scale_events[e].phi_obs - phi_lo) / std::max(1e-9, phi_hi - phi_lo)), 0, 4);
}
});
// Robust-loss scale from the scatter the events actually have: it varies by more than a decade
// between datasets, so any fixed constant is either inert or throws away real data. Taken once,
// over every event, so the all-data fit and every jackknife fold share it.
const auto residual_at = [&](const ScaleTerm &t, double k) {
return static_cast<double>(t.C)
+ static_cast<double>(t.R) * std::cos(static_cast<double>(t.a) * k + t.psi);
};
double rms = 0.0;
for (const auto &t : terms) {
const double r = residual_at(t, 1.0);
rms += r * r;
}
rms = std::sqrt(rms / static_cast<double>(terms.size()));
const double huber_delta = std::max(1e-12, 2.0 * rms);
const double huber_d2 = huber_delta * huber_delta;
// Ceres minimises half the sum of the loss applied to the SQUARED residual, so that is what is
// reproduced here. One pass yields the five per-fifth partial sums, which serve the all-data
// fit and all five leave-a-fifth-out folds together.
const auto cost_by_fifth = [&](double k) {
std::array<double, 5> total{};
std::mutex mx;
ParallelChunks(static_cast<int>(terms.size()), nthreads, [&](int lo, int hi) {
std::array<double, 5> acc{};
for (int e = lo; e < hi; ++e) {
const double r = residual_at(terms[e], k);
const double s2 = r * r;
acc[fifth_of[e]] += (s2 <= huber_d2) ? s2
: (2.0 * huber_delta * std::sqrt(s2) - huber_d2);
}
std::unique_lock ul(mx);
for (int j = 0; j < 5; ++j) total[j] += acc[j];
});
return total;
};
// Scan the interval Ceres was bounded to, then close in. No event's phase can move by more than
// a fraction of a period over an interval this narrow, so the objective has no structure the
// grid could step over; the refinement is only there to place the minimum precisely.
constexpr int SCALE_GRID = 101;
constexpr double SCALE_K_LO = 0.95, SCALE_K_HI = 1.05;
std::vector<std::array<double, 5>> grid(SCALE_GRID);
for (int g = 0; g < SCALE_GRID; ++g)
grid[g] = cost_by_fifth(SCALE_K_LO + (SCALE_K_HI - SCALE_K_LO) * g / (SCALE_GRID - 1));
auto solve_scale = [&](int drop_fifth) {
const auto total = [&](const std::array<double, 5> &f) {
double t = 0.0;
for (int j = 0; j < 5; ++j)
if (j != drop_fifth) t += f[j];
return t;
};
int best = 0;
for (int g = 1; g < SCALE_GRID; ++g)
if (total(grid[g]) < total(grid[best])) best = g;
const double step = (SCALE_K_HI - SCALE_K_LO) / (SCALE_GRID - 1);
double a = std::max(SCALE_K_LO, SCALE_K_LO + step * (best - 1));
double b = std::min(SCALE_K_HI, SCALE_K_LO + step * (best + 1));
// Golden section: the objective is smooth but its curvature jumps wherever an event
// crosses the Huber knee, which a derivative method would have to cope with.
constexpr double INV_PHI = 0.6180339887498949;
double c = b - INV_PHI * (b - a), d = a + INV_PHI * (b - a);
double fc = total(cost_by_fifth(c)), fd = total(cost_by_fifth(d));
while (b - a > 1e-9) {
if (fc < fd) { b = d; d = c; fd = fc; c = b - INV_PHI * (b - a); fc = total(cost_by_fifth(c)); }
else { a = c; c = d; fc = fd; d = a + INV_PHI * (b - a); fd = total(cost_by_fifth(d)); }
}
return 0.5 * (a + b);
};
const double k_fit = solve_scale(-1);
result.rotation_scale = k_fit;
// ----- Whether to COMMIT it. A stage fault is rare - 36 of 37 rotation datasets sit at 1.0000
// on a direct scan - and a 1 % angle correction applied to a healthy dataset would damage it
// silently, so every test below has to pass.
// Preconditions: below these the fit is reported but never acted on. Under ~30 deg of sweep k
// entangles with the axis direction and 10-20 deg truncations of a perfect dataset wander by
// +-0.6 %; a screening wedge must not trigger a correction.
constexpr int MIN_SCALE_EVENTS = 5000;
constexpr double MIN_SCALE_SWEEP_DEG = 30.0;
// T1 significance: 0.5 % is 18 sigma on the between-dataset scatter of healthy stages
// (robust sd 2.8e-4) and still 3.5x below the one measured fault.
constexpr double ROTATION_SCALE_TOL = 0.005;
// T2 relevance: the misorientation the error produces at each end of the sweep. A large k over
// a short sweep moves nothing and is not worth correcting.
constexpr double MIN_SCALE_END_ERROR_DEG = 0.5;
// T3 uniformity: a stage error is a ramp present in EVERY part of the sweep, so dropping any
// fifth of it must leave the same k. A second lattice that dominates ONE END of the sweep -
// exactly what happens where the primary stops indexing - fakes a k indistinguishable from a
// real fault on T1 and T2, and is the reason this test is not optional. It replaces the
// hkl-hash split used elsewhere here, which cannot see it: both halves of that split sit at
// the same angles, so anything structured in phi survives in both folds.
constexpr double MIN_SCALE_JACKKNIFE_FRAC = 0.5;
const double end_error_deg = std::fabs(k_fit - 1.0) * sweep_deg / 2.0;
const bool enough_data = static_cast<int>(scale_events.size()) >= MIN_SCALE_EVENTS
&& sweep_deg >= MIN_SCALE_SWEEP_DEG;
const bool big_enough = enough_data && std::fabs(k_fit - 1.0) >= ROTATION_SCALE_TOL
&& end_error_deg >= MIN_SCALE_END_ERROR_DEG;
double jackknife = 1.0;
if (big_enough)
for (int f = 0; f < 5; ++f)
jackknife = std::min(jackknife, (solve_scale(f) - 1.0) / (k_fit - 1.0));
result.rotation_scale_suspect = big_enough && jackknife >= MIN_SCALE_JACKKNIFE_FRAC;
logger.Info("Post-refine rotation SCALE: k = {:.5f} over {:.0f} deg of sweep centred on {:.1f} "
"deg ({} events): end error {:.2f} deg, leave-a-fifth-out {:.2f} => {}",
k_fit, sweep_deg, phi_c * 180.0 / PI, scale_events.size(), end_error_deg, jackknife,
result.rotation_scale_suspect ? "COMMIT"
: !enough_data ? "report only (too little sweep or too few events)"
: "reject (kept the stored angles)");
if (result.rotation_scale_suspect)
logger.Warning("Goniometer rotation scale looks off by {:+.2f} % (fitted {:.5f}): the stage "
"appears to have turned {} than the angles stored in the file, which are the "
"COMMANDED values. This is a hardware calibration fault, not a data problem - "
"left uncorrected it inflates mosaicity, biases the cell and loses "
"high-resolution reflections",
100.0 * (k_fit - 1.0), k_fit, k_fit > 1.0 ? "further" : "less far");
// Cell (scale s, shape fixed) as the XtalResidual parameter blocks p0/p1/p2, held CONSTANT in step B.
double p0[3] = {0, 0, 0}, p1[3] = {0, 0, 0}, p2[3] = {0, 0, 0};
double beta = r0.beta;
switch (sys) {
case gemmi::CrystalSystem::Tetragonal:
LatticeToRodriguesAndLengths_GS(reference_latt, p0, p1);
p1[0] = (p1[0] + p1[1]) / 2.0; break;
case gemmi::CrystalSystem::Cubic:
LatticeToRodriguesAndLengths_GS(reference_latt, p0, p1);
p1[0] = (p1[0] + p1[1] + p1[2]) / 3.0; break;
case gemmi::CrystalSystem::Hexagonal:
LatticeToRodriguesAndLengths_Hex(reference_latt, p0, p1); break;
case gemmi::CrystalSystem::Monoclinic:
LatticeToRodriguesLengthsBeta_Mono(reference_latt, p0, p1, beta);
p2[0] = beta; break;
case gemmi::CrystalSystem::Orthorhombic:
LatticeToRodriguesAndLengths_GS(reference_latt, p0, p1); break;
default:
LatticeToRodriguesAndLengths_GS(reference_latt, p0, p1);
p2[0] = r0.alpha * PI / 180.0; p2[1] = r0.beta * PI / 180.0; p2[2] = r0.gamma * PI / 180.0; break;
}
for (int j = 0; j < 3; ++j) p1[j] *= s; // apply the committed cell scale
double rot_vec[3] = {axv[0], axv[1], axv[2]}; // committed (or nominal) axis
// ===== Step B: detector distance + beam from the observed positions, cell fixed =====
std::vector<const Partial *> obs;
for (const auto &pp : pts)
if (std::isfinite(pp.obs_x) && std::isfinite(pp.obs_y)) obs.push_back(&pp);
constexpr size_t MAX_OBS = 20000;
if (obs.size() > MAX_OBS) {
std::nth_element(obs.begin(), obs.begin() + MAX_OBS, obs.end(),
[](const Partial *a, const Partial *b) {
return a->I / std::max(1e-9, a->sigma) > b->I / std::max(1e-9, b->sigma); });
obs.resize(MAX_OBS);
}
result.obs_used = static_cast<int>(obs.size());
const double beam_x0 = nominal_geom.GetBeamX_pxl(), beam_y0 = nominal_geom.GetBeamY_pxl();
const double dist0 = nominal_geom.GetDetectorDistance_mm();
auto pos_cost = [&](Subset s, const double beam[2], const double dist[1]) {
double c = 0.0; int n = 0;
for (const Partial *pp : obs) {
if (!in(pp->h, pp->k, pp->l, s)) continue;
XtalResidual r(pp->obs_x, pp->obs_y, lambda_l, pixel_mm, rot3, pp->angle_rad,
pp->h, pp->k, pp->l, sys);
double resid[3] = {0, 0, 0};
r(beam, dist, det_rot, rot_vec, p0, p1, p2, resid);
c += resid[0]*resid[0] + resid[1]*resid[1] + resid[2]*resid[2]; ++n;
}
return n ? c / n : 0.0;
};
auto solve_detector = [&](Subset s, double beam_out[2], double &dist_out) {
double beam[2] = {beam_x0, beam_y0}, dist[1] = {dist0};
ceres::Problem p;
for (const Partial *pp : obs) {
if (!in(pp->h, pp->k, pp->l, s)) continue;
p.AddResidualBlock(new ceres::AutoDiffCostFunction<XtalResidual, 3, 2, 1, 2, 3, 3, 3, 3>(
new XtalResidual(pp->obs_x, pp->obs_y, lambda_l, pixel_mm, rot3, pp->angle_rad,
pp->h, pp->k, pp->l, sys)),
new ceres::CauchyLoss(0.02), beam, dist,
const_cast<double *>(det_rot), rot_vec, p0, p1, p2);
p.SetParameterBlockConstant(const_cast<double *>(det_rot));
p.SetParameterBlockConstant(rot_vec);
p.SetParameterBlockConstant(p0); p.SetParameterBlockConstant(p1); p.SetParameterBlockConstant(p2);
}
if (p.NumResidualBlocks() == 0) { beam_out[0] = beam_x0; beam_out[1] = beam_y0; dist_out = dist0; return false; }
p.SetParameterLowerBound(dist, 0, dist0 * 0.95); p.SetParameterUpperBound(dist, 0, dist0 * 1.05);
for (int j = 0; j < 2; ++j) { p.SetParameterLowerBound(beam, j, beam[j] - 15.0);
p.SetParameterUpperBound(beam, j, beam[j] + 15.0); }
ceres::Solver::Options o; o.linear_solver_type = ceres::DENSE_QR; o.max_num_iterations = 60;
o.num_threads = std::max(1, settings.num_threads); o.logging_type = ceres::LoggingType::SILENT;
ceres::Solver::Summary sum; ceres::Solve(o, &p, &sum);
beam_out[0] = beam[0]; beam_out[1] = beam[1]; dist_out = dist[0];
return sum.IsSolutionUsable();
};
double beam[2] = {beam_x0, beam_y0}, dist = dist0;
if (obs.size() >= static_cast<size_t>(settings.min_events)) {
double beam_fit[2], dist_fit;
const bool convB = solve_detector(FIT, beam_fit, dist_fit);
const double b_nom[2] = {beam_x0, beam_y0}, d_nom[1] = {dist0};
const double b_ref[2] = {beam_fit[0], beam_fit[1]}, d_ref[1] = {dist_fit};
const double cvB_nom = pos_cost(VAL, b_nom, d_nom);
const double cvB_ref = pos_cost(VAL, b_ref, d_ref);
// Commit the detector geometry only for a small, credible move: distance < 1 % (a calibrated
// header needs < ~0.6 %). A larger move is the red flag for an unreliable fit - typically a
// second lattice whose spots bias every cross-validation fold identically, so the relative
// "it improved" gate is blind to it and pulls a spurious distance<->cell pair (the radial
// degeneracy) far off. The absolute size of the move discriminates a genuine header correction
// from that failure far better than the absolute residual, which real marginal (noisy / iced)
// data shares with the multi-lattice case.
const bool in_bounds = std::fabs(dist_fit - dist0) < 0.01 * dist0
&& std::hypot(beam_fit[0] - beam_x0, beam_fit[1] - beam_y0) < 15.0;
result.detector_refined = convB && cvB_ref < 0.98 * cvB_nom && in_bounds;
if (result.detector_refined) { double bo[2]; solve_detector(ALL, bo, dist); beam[0] = bo[0]; beam[1] = bo[1]; }
logger.Info("Post-refine GEOM step B (distance/beam): dist {:.3f} -> {:.3f} mm, beam "
"({:.2f},{:.2f}) -> ({:.2f},{:.2f}), held-out pos {:.3e} -> {:.3e} => {}",
dist0, result.detector_refined ? dist : dist0, beam_x0, beam_y0,
result.detector_refined ? beam[0] : beam_x0, result.detector_refined ? beam[1] : beam_y0,
cvB_nom, cvB_ref, result.detector_refined ? "COMMIT" : "reject (kept nominal detector)");
} else {
logger.Info("Post-refine GEOM step B: only {} positional observations - skipped", obs.size());
}
// Assemble the committed geometry.
UnitCell cellA = r0;
if (result.cell_refined) { cellA.a = static_cast<float>(r0.a * s); cellA.b = static_cast<float>(r0.b * s);
cellA.c = static_cast<float>(r0.c * s); }
result.cell = cellA;
result.distance_after_mm = dist;
result.beam_x_before_px = beam_x0; result.beam_x_after_px = beam[0];
result.beam_y_before_px = beam_y0; result.beam_y_after_px = beam[1];
result.events_used = static_cast<int>(events.size());
result.ok = result.cell_refined || result.detector_refined;
if (!result.ok)
logger.Info("Post-refine GEOM: neither step passed cross-validation - geometry left at nominal");
return result;
}
return result; // refine_geometry is the only supported mode; nothing refined otherwise
} catch (...) {
result.ok = false;
return result;
}
}