lsst.ip.diffim.modelPsfMatch Namespace Reference

Classes
class	ModelPsfMatchConfig
class	ModelPsfMatchTask
class	PsfComputeShapeError
class	WarpedPsfTransformTooBigError

Functions
	_safeEstimateRoughShape (psf, position, jitter=2.0, maxTries=5, log=None)
	nextOddInteger (x)

Variables
int	sigma2fwhm = 2.*np.sqrt(2.*np.log(2.))

Function Documentation

_safeEstimateRoughShape()

lsst.ip.diffim.modelPsfMatch._safeEstimateRoughShape ( psf, position, jitter = 2.0, maxTries = 5, log = None )

protected

Try to compute the shape of `psf` at `position`.

If it fails, perturb the position until success or maxTries.

Parameters
----------
psf : `lsst.afw.detection.Psf`
    The PSF object.
position : `lsst.geom.Point2D`
    The nominal position at which to evaluate the PSF shape.
jitter : `float`
    Size of random offset in pixels to try when retrying.
maxTries : `int`
    Maximum number of attempts (including the original).
log : `lsst.utils.logging.LsstLogAdapter` optional
    logger to use for logging retries.

Returns
-------
shape : lsst.afw.geom.ellipses.Quadrupole
    The shape of the PSF at the (possibly perturbed) position.

Definition at line 48 of file modelPsfMatch.py.

def _safeEstimateRoughShape(psf, position, jitter=2.0, maxTries=5, log=None):
 
    """
    Try to compute the shape of `psf` at `position`.
 
    If it fails, perturb the position until success or maxTries.
 
    Parameters
    ----------
    psf : `lsst.afw.detection.Psf`
        The PSF object.
    position : `lsst.geom.Point2D`
        The nominal position at which to evaluate the PSF shape.
    jitter : `float`
        Size of random offset in pixels to try when retrying.
    maxTries : `int`
        Maximum number of attempts (including the original).
    log : `lsst.utils.logging.LsstLogAdapter` optional
        logger to use for logging retries.
 
    Returns
    -------
    shape : lsst.afw.geom.ellipses.Quadrupole
        The shape of the PSF at the (possibly perturbed) position.
    """
    try:
        return psf.computeShape(position)
    except pexExceptions.Exception as err:
        if log:
            log.info(f"safeEstimateRoughShape: initial evaluation of PSF failed with message: {str(err)}."
                     " Retrying nearby")
        firstErr = err
 
    # random offsets must be deterministic
    offsets = np.random.default_rng(seed=40).uniform(-jitter, jitter, size=(maxTries - 1, 2))
    candidates = [position + geom.Extent2D(dx, dy) for dx, dy in offsets]
    for i, candidate in enumerate(candidates):
        try:
            shape = psf.computeShape(candidate)
            if log:
                log.info(f"safeEstimateRoughShape succeeded on try {i + 2} at position {candidate}")
            return shape
        except pexExceptions.Exception:
            continue
 
    # If nothing worked, raise AlgorithmError from original position
    raise PsfComputeShapeError(position) from firstErr
 
 

nextOddInteger()

lsst.ip.diffim.modelPsfMatch.nextOddInteger

(

x

)

Definition at line 97 of file modelPsfMatch.py.

def nextOddInteger(x):
    nextInt = int(np.ceil(x))
    return nextInt + 1 if nextInt%2 == 0 else nextInt
 
 

Variable Documentation

sigma2fwhm

int lsst.ip.diffim.modelPsfMatch.sigma2fwhm = 2.*np.sqrt(2.*np.log(2.))

Definition at line 45 of file modelPsfMatch.py.