Add UnitLogGauss

nifty4/library/unit_log_gauss.py

+from ..minimization import Energy
+from ..operators import InversionEnabler, SandwichOperator
+from ..utilities import memo
+
+
+class UnitLogGauss(Energy):
+    def __init__(self, position, s, inverter=None):
+        """
+        s: Sky model object
+
+        value = 0.5 * s.vdot(s), i.e. a log-Gauss distribution with unit
+        covariance
+        """
+        super(UnitLogGauss, self).__init__(position)
+        self._s = s.at(position)
+        self._inverter = inverter
+
+    def at(self, position):
+        return self.__class__(position, self._s, self._inverter)
+
+    @property
+    @memo
+    def _gradient_helper(self):
+        return self._s.gradient
+
+    @property
+    @memo
+    def value(self):
+        return .5 * self._s.value.vdot(self._s.value)
+
+    @property
+    @memo
+    def gradient(self):
+        return self._gradient_helper.adjoint(self._s.value)
+
+    @property
+    @memo
+    def curvature(self):
+        c = SandwichOperator.make(self._gradient_helper)
+        if self._inverter is None:
+            return c
+        return InversionEnabler(c, self._inverter)