lsst::meas::base::SafeShapeExtractor Class Reference

Utility class for measurement algorithms that extracts an ellipse from the Shape slot and handles errors in a safe and consistent way. More...

#include <InputUtilities.h>

Public Member Functions
	SafeShapeExtractor (afw::table::Schema &schema, std::string const &name)
	Construct the extractor, creating a flag alias that indicates failure in the input centroid by linking to the slot shape flag. More...
afw::geom::ellipses::Quadrupole	operator() (afw::table::SourceRecord &record, FlagHandler const &flags) const
	Extract a shape from the given record. More...

Detailed Description

Utility class for measurement algorithms that extracts an ellipse from the Shape slot and handles errors in a safe and consistent way.

Definition at line 90 of file InputUtilities.h.

Constructor & Destructor Documentation

SafeShapeExtractor()

lsst::meas::base::SafeShapeExtractor::SafeShapeExtractor	(	afw::table::Schema &	schema,
		std::string const &	name
	)

Construct the extractor, creating a flag alias that indicates failure in the input centroid by linking to the slot shape flag.

Parameters

[out]	schema	Schema to which the alias should be added. The "slot_Shape" alias must already be present in the Schema's AliasMap.
[in]	name	The name of the algorithm; the flag alias added will be "<name>_flag_badShape".

Definition at line 133 of file InputUtilities.cc.

                                                                                    : _name(name) {
    // Instead of aliasing e.g. MyAlgorithm_flag_badShape->slot_Shape_flag, we actually
    // look up the target of slot_Shape_flag, and alias that to MyAlgorithm_flag_badCentroid.
    // That way, if someone changes the slots later, after we've already done the measurement,
    // this alias still points to the right thing.
    std::string aliasedFlagName = schema.join("slot", "Shape", "flag");
    std::string slotFlagName = schema.getAliasMap()->apply(aliasedFlagName);
    if (aliasedFlagName == slotFlagName) {
        throw LSST_EXCEPT(pex::exceptions::LogicError,
                          (boost::format("Alias for '%s' must be defined before initializing '%s' plugin.") %
                           aliasedFlagName % name)
                                  .str());
    }
    schema.getAliasMap()->set(schema.join(name, "flag", "badShape"), slotFlagName);
}

Member Function Documentation

operator()()

afw::geom::ellipses::Quadrupole lsst::meas::base::SafeShapeExtractor::operator()	(	afw::table::SourceRecord &	record,
		FlagHandler const &	flags
	)		const

Extract a shape from the given record.

We use the Shape slot if it is not NaN, and throw MeasurementError if it is (with only the general failure code attached to the MeasurementError).

If the Shape slot is not defined, we throw FatalAlgorithmError, as this indicates a configuration problem.

If the Shape slot value is NaN and is not flagged (or there is no Shape slot flag), we throw RuntimeError, which should cause the measurement framework to log a warning and set the current algorithm's general failure flag if it is allowed to propagate out of the algorithm implementation.

If the Shape slot is flagged and we nevertheless obtain a usable ellipse, we set the current algorithm's general failure flag, but return the ellipse as well, allowing it to continue while indicating that the result may not be reliable. A singular ellipse (i.e. one with a non-positive quadrupole matrix determinant) is treated the same as a NaN ellipse; it is not considered usable.

Definition at line 149 of file InputUtilities.cc.

                                                                                               {
    if (!record.getTable()->getCentroidSlot().getMeasKey().isValid()) {
        throw LSST_EXCEPT(
                FatalAlgorithmError,
                (boost::format("%s requires a shape, but the shape slot is not defined") % _name).str());
    }
    afw::geom::ellipses::Quadrupole result = record.getShape();
    if (std::isnan(result.getIxx()) || std::isnan(result.getIyy()) || std::isnan(result.getIxy()) ||
        result.getIxx() * result.getIyy() < (1.0 + 1.0e-6) * result.getIxy() * result.getIxy()
        // We are checking that Ixx*Iyy > (1 + epsilon)*Ixy*Ixy where epsilon is suitably small. The
        // value of epsilon used here is a magic number. DM-5801 is supposed to figure out if we are
        // to keep this value.
    ) {
        if (!record.getTable()->getShapeSlot().getFlagKey().isValid()) {
            throw LSST_EXCEPT(
                    pex::exceptions::RuntimeError,
                    (boost::format("%s: Shape slot value is NaN, but there is no Shape slot flag "
                                   "(is the executionOrder for %s lower than that of the slot Shape?)") %
                     _name % _name)
                            .str());
        }
        if (!record.getShapeFlag()) {
            throw LSST_EXCEPT(
                    pex::exceptions::RuntimeError,
                    (boost::format("%s: Shape slot value is NaN, but the Shape slot flag is not set "
                                   "(is the executionOrder for %s lower than that of the slot Shape?)") %
                     _name % _name)
                            .str());
        }
        throw LSST_EXCEPT(
                MeasurementError,
                (boost::format("%s: Shape needed, and Shape slot measurement failed.") % _name).str(),
                flags.getFailureFlagNumber());
    } else if (record.getTable()->getShapeSlot().getFlagKey().isValid() && record.getShapeFlag()) {
        // we got a usable value, but the shape flag might still be set, and that might affect
        // the current measurement
        flags.setValue(record, flags.getFailureFlagNumber(), true);
    }
    return result;
}

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The documentation for this class was generated from the following files:

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/meas_base/22.0.1-25-gb120d7b+8b5510f75f/include/lsst/meas/base/InputUtilities.h
• /j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/meas_base/22.0.1-25-gb120d7b+8b5510f75f/src/InputUtilities.cc