add NullOperator

nifty5/models/constant.py

@@ -18,6 +18,7 @@
 
 from __future__ import absolute_import, division, print_function
 from ..compat import *
+from ..operators.null_operator import NullOperator
 from .model import Model
 
 
@@ -43,7 +44,7 @@ class Constant(Model):
         self._constant = constant
 
         self._value = self._constant
-        self._jacobian = 0.
+        self._jacobian = NullOperator(position.domain, constand.domain)
 
     def at(self, position):
         return self.__class__(position, self._constant)

nifty5/multi/multi_field.py

@@ -30,7 +30,7 @@ class MultiField(object):
         Parameters
         ----------
         domain: MultiDomain
-        val: tuple of Fields
+        val: tuple containing Field or None entries
         """
         if not isinstance(domain, MultiDomain):
             raise TypeError("domain must be of type MultiDomain")
@@ -38,12 +38,12 @@ class MultiField(object):
             raise TypeError("val must be a tuple")
         if len(val) != len(domain):
             raise ValueError("length mismatch")
-        for i, v in enumerate(val):
+        for d, v in zip(domain._domains, val):
             if isinstance(v, Field):
-                if v._domain is not domain._domains[i]:
+                if v._domain is not d:
                     raise ValueError("domain mismatch")
             elif v is not None:
-                raise TypeError("bad entry in val")
+                raise TypeError("bad entry in val (must be Field or None)")
         self._domain = domain
         self._val = val
 

nifty5/operators/null_operator.py

+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# Copyright(C) 2013-2018 Max-Planck-Society
+#
+# NIFTy is being developed at the Max-Planck-Institut fuer Astrophysik
+# and financially supported by the Studienstiftung des deutschen Volkes.
+
+from __future__ import absolute_import, division, print_function
+from ..compat import *
+from ..domain_tuple import DomainTuple
+from ..field import Field
+from ..multi.multi_field import MultiField
+from ..operators.linear_operator import LinearOperator
+
+
+class NullOperator(LinearOperator):
+    """Operator corresponding to a matrix of all zeros.
+
+    Parameters
+    ----------
+    domain : DomainTuple or MultiDomain
+        input domain
+    target : DomainTuple or MultiDomain
+        output domain
+    """
+    def __init__(self, domain, target):
+        from ..sugar import makeDomain
+        self._domain = makeDomain(domain)
+        self._target = makeDomain(target)
+
+    @staticmethod
+    def _nullfield(dom):
+        if isinstance (dom, DomainTuple):
+            return Field.full(self._target, 0)
+        else:
+            return MultiField(dom, (None,)*len(dom))
+
+    def apply(self, x, mode):
+        self._check_input(x, mode)
+
+        if mode == self.TIMES:
+            return self._nullfield(self._target)
+        return self._nullfield(self._domain)
+
+    @property
+    def domain(self):
+        return self._domain
+
+    @property
+    def target(self):
+        return self._target
+
+    @property
+    def capability(self):
+        return self.TIMES | self.ADJOINT_TIMES