Stability controls for the bfcorr BField domain walk

Fit/Config.cc

@@ -8,8 +8,13 @@ namespace KinKal {
       << " diverge dpar chisq " << kkconfig.pdchisq_
       << " diverge traj gap (mm) " << kkconfig.divgap_
       << " fractional momentum tolerance " << kkconfig.tol_
+      << " min domain step (ns) " << kkconfig.mindtstep_
+      << " min field (T) " << kkconfig.minfield_
+      << " domain margin (ns) " << kkconfig.domainmargin_
+      << " max domains " << kkconfig.maxdomains_
       << " min NDOF " << kkconfig.minndof_
       << " BField correction " << kkconfig.bfcorr_
+      << " zero-field extrap handoff " << kkconfig.zerofield_extrap_
       << " with " << kkconfig.schedule().size()
       << " Meta-iterations:" << std::endl;
     for(auto const& miconfig : kkconfig.schedule() ) {

Fit/Config.hh

@@ -11,6 +11,7 @@
 #include <vector>
 #include <memory>
 #include <algorithm>
+#include <limits>
 #include <ostream>
 #include <istream>
 
@@ -29,8 +30,13 @@ namespace KinKal {
     double pdchisq_ = 1.0e6; // maximum allowed parameter change (units of chisqred) WRT previous reference
     double divgap_ = 1.0e2; // maximum average gap of trajectory before calling it diverged (mm)
     double tol_ = 1.0e-4; // tolerance on fractional momentum accuracy due to BField domain steps
+    double mindtstep_ = 0.0; // ns: hard floor on the BField domain step (0 = legacy; >0 bounds the domain count where rangeInTolerance->0)
+    double minfield_ = 0.0; // T: if >0, and zerofield_extrap_ is enabled, hand bfcorr extrapolation off to free-particle continuation once |B| drops below this
+    double domainmargin_ = std::numeric_limits<double>::max(); // ns: max time a fit domain may extend beyond the active range (max = unclamped/legacy overhang; finite = confine walk+sampling to range±margin)
+    unsigned maxdomains_ = std::numeric_limits<unsigned>::max(); // hard cap on BField domains per fit; over-cap fits fail cleanly (max = unlimited/legacy)
     unsigned minndof_ = 5; // minimum number of DOFs to continue fit
     bool bfcorr_ = true; // whether to make BFieldMap corrections in the fit
+    bool zerofield_extrap_ = false; // if true: (1) bfcorr extrapolate() hands off to geometric free-particle continuation outside the map / below minfield_; (2) createDomains stops DomainWalls at that edge instead of failing Extension; (3) replaceDomains charge/mass mismatch soft-keeps the prior usable fit (CH cosmic CRV). Default false preserves legacy LH/CH behaviour.
     bool ends_ = true; // process the passive effects at each end of the track after schedule completion
     printLevel plevel_ = none; // print level
     // schedule of meta-iterations.  These will be executed sequentially until completion or failure