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DM-14740: Stop using ndarray::EigenView indirectly in C++ code #119

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Jun 18, 2018
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DM-14740: Stop using ndarray::EigenView indirectly in C++ code #119

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cb55f0a
Stop using ndarray::Array::asEigen
r-owen Jun 11, 2018
a15a200
Use matrices instead of arrays
r-owen Jun 13, 2018
3d1d941
Name improvement
r-owen Jun 13, 2018
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29 changes: 15 additions & 14 deletions src/PsfFlux.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -93,22 +93,23 @@ void PsfFluxAlgorithm::measure(afw::table::SourceRecord& measRecord,
throw LSST_EXCEPT(MeasurementError, NO_GOOD_PIXELS.doc, NO_GOOD_PIXELS.number);
}
typedef afw::detection::Psf::Pixel PsfPixel;
auto model = fitRegion.getSpans()
->flatten(psfImage->getArray(), psfImage->getXY0())
.asEigen<Eigen::ArrayXpr>();
auto data = fitRegion.getSpans()
->flatten(exposure.getMaskedImage().getImage()->getArray(), exposure.getXY0())
.asEigen<Eigen::ArrayXpr>();
auto variance = fitRegion.getSpans()
->flatten(exposure.getMaskedImage().getVariance()->getArray(), exposure.getXY0())
.asEigen<Eigen::ArrayXpr>();
PsfPixel alpha = model.matrix().squaredNorm();
// SpanSet::flatten returns a new ndarray::Array, which must stay in scope
// while we use an Eigen::Map view of it
auto modelNdArray = fitRegion.getSpans()->flatten(psfImage->getArray(), psfImage->getXY0());
auto dataNdArray = fitRegion.getSpans()->flatten(exposure.getMaskedImage().getImage()->getArray(),
exposure.getXY0());
auto varianceNdArray = fitRegion.getSpans()->flatten(exposure.getMaskedImage().getVariance()->getArray(),
exposure.getXY0());
auto model = ndarray::asEigenMatrix(modelNdArray);
auto data = ndarray::asEigenMatrix(dataNdArray);
auto variance = ndarray::asEigenMatrix(varianceNdArray);
PsfPixel alpha = model.squaredNorm();
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Why are these asEigenMatrix rather than asEigenArray? The original code used asEigen<Eigen::ArrayXpr>.

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Because in almost all cases in the old code the array EigenView is used as a matrix by appending .matrix(). This eliminates all those calls to .matrix() at the expense of adding one call to .array(). See the changes below.

FluxResult result;
result.flux = model.matrix().dot(data.matrix().cast<PsfPixel>()) / alpha;
result.flux = model.dot(data.cast<PsfPixel>()) / alpha;
// If we're not using per-pixel weights to compute the flux, we'll still want to compute the
// variance as if we had, so we'll apply the weights to the model vector now, and update alpha.
result.fluxSigma = std::sqrt(model.square().matrix().dot(variance.matrix().cast<PsfPixel>())) / alpha;
measRecord.set(_areaKey, model.matrix().sum() / alpha);
// variance as if we had, so we'll apply the weights to the model now, and update alpha.
result.fluxSigma = std::sqrt(model.array().square().matrix().dot(variance.cast<PsfPixel>())) / alpha;
measRecord.set(_areaKey, model.sum() / alpha);
if (!std::isfinite(result.flux) || !std::isfinite(result.fluxSigma)) {
throw LSST_EXCEPT(PixelValueError, "Invalid pixel value detected in image.");
}
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