From fa6b5343cc649bac10fefba7f72df7087ecb1b9c Mon Sep 17 00:00:00 2001
From: Zhenwen Dai <z.dai@sheffield.ac.uk>
Date: Mon, 23 Jun 2014 14:37:11 +0100
Subject: [PATCH] merge ties branch into psi2

---
 .../parameterization/ties_and_remappings.py   | 80 +++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 GPy/core/parameterization/ties_and_remappings.py

diff --git a/GPy/core/parameterization/ties_and_remappings.py b/GPy/core/parameterization/ties_and_remappings.py
new file mode 100644
index 00000000..75b46a95
--- /dev/null
+++ b/GPy/core/parameterization/ties_and_remappings.py
@@ -0,0 +1,80 @@
+# Copyright (c) 2014, James Hensman, Max Zwiessele
+# Licensed under the BSD 3-clause license (see LICENSE.txt)
+
+import numpy as np
+from parameterized import Parameterized
+from param import Param
+
+class Remapping(Parameterized):
+    def mapping(self):
+        """
+        The return value of this function gives the values which the re-mapped
+        parameters should take. Implement in sub-classes.
+        """
+        raise NotImplementedError
+
+    def callback(self):
+        raise NotImplementedError
+
+    def __str__(self):
+        return self.name
+
+    def parameters_changed(self):
+        #ensure all out parameters have the correct value, as specified by our mapping
+        index = self._highest_parent_.constraints[self]
+        self._highest_parent_.param_array[index] = self.mapping()
+        [p.notify_observers(which=self) for p in self.tied_parameters]
+
+class Fix(Remapping):
+    pass
+
+
+
+
+class Tie(Remapping):
+    def __init__(self, value, name):
+        super(Tie, self).__init__(name)
+        self.tied_parameters = []
+        self.value = Param('val', value)
+        self.add_parameter(self.value)
+
+    def add_tied_parameter(self, p):
+        self.tied_parameters.append(p)
+        p.add_observer(self, self.callback)
+        self.parameters_changed()
+
+    def callback(self, param=None, which=None):
+        """
+        This gets called whenever any of the tied parameters changes. we spend
+        considerable effort working out whhat has changed ant to what value.
+        Then we store that value in self.value, and broadcast it everywhere
+        with parameters_changed.
+        """
+        if which is self:return
+        index = self._highest_parent_.constraints[self]
+        if len(index)==0:
+            return # nothing to tie together, this tie exists without any tied parameters
+        vals = self._highest_parent_.param_array[index]
+        uvals = np.unique(vals)
+        if len(uvals)==1:
+            #all of the tied things are at the same value
+            self.value[...] = uvals[0]
+        elif len(uvals)==2:
+            #only *one* of the tied things has changed. it must be different to self.value
+            newval = uvals[uvals != self.value*1]
+            self.value[...] = newval
+        else:
+            #more than one of the tied things changed. panic.
+            raise ValueError, "something is wrong with the tieing"
+
+    def mapping(self):
+        return self.value
+
+    def collate_gradient(self):
+        index = self._highest_parent_.constraints[self]
+        self.value.gradient = np.sum(self._highest_parent_.gradient[index])
+
+
+
+
+