# HG changeset patch
# User Olivier Delalleau <delallea@iro>
# Date 1243266230 14400
# Node ID 88f5b75a4afe38707c10313e9b3e0f4760e3d7ab
# Parent  bf29e201515fb23f5b859ae12e83230e7ebca9af
Added new option 'ignore_missing' to deal with missing values in input

diff -r bf29e201515f -r 88f5b75a4afe pylearn/algorithms/sandbox/DAA_inputs_groups.py
--- a/pylearn/algorithms/sandbox/DAA_inputs_groups.py	Mon May 25 11:42:25 2009 -0400
+++ b/pylearn/algorithms/sandbox/DAA_inputs_groups.py	Mon May 25 11:43:50 2009 -0400
@@ -46,12 +46,26 @@
     def __init__(self, input = None, auxinput = None,
                 in_size=None, auxin_size= None, n_hid=1,
                 regularize = False, tie_weights = False, hid_fn = 'sigmoid_act',
-                reconstruction_cost_function=cost.cross_entropy, interface = True,**init):
+                reconstruction_cost_function=cost.cross_entropy, interface = True,
+                ignore_missing=False,
+                **init):
         """
         :param regularize: WRITEME
         :param tie_weights: WRITEME
         :param hid_fn: WRITEME
         :param reconstruction_cost: Should return one cost per example (row)
+        :param ignore_missing: if True, the input will be scanned in order to
+            detect missing values, and these values will be replaced by zeros.
+            Also, the reconstruction cost will be computed only on non missing
+            components.
+            If False, the presence of missing values may cause crashes or other
+            weird and unexpected behavior.
+            Please note that this option only affects the permanent input, not
+            auxilary ones (that should never contain missing values). In fact,
+            in the current implementation, auxiliary inputs cannot be used when
+            this option is True.
+            Another side effect of the current crappy way it is implemented is
+            that the reconstruction cost is not properly computed.
         :todo: Default noise level for all daa levels
         """
         print '\t\t**** DAAig.__init__ ****'
@@ -72,12 +86,19 @@
         self.tie_weights = tie_weights
         self.reconstruction_cost_function = reconstruction_cost_function
         self.interface = interface
+        self.ignore_missing = ignore_missing
         
         assert hid_fn in ('sigmoid_act','tanh_act','softsign_act')
         self.hid_fn = eval(hid_fn)
         
         ### DECLARE MODEL VARIABLES and default
         self.input = input
+        if self.ignore_missing and self.input is not None:
+            no_missing = fill_missing_with_zeros(self.input)
+            self.input = no_missing[0]  # Missing values replaced by zeros.
+            self.input_missing_mask = no_missing[1] # Missingness pattern.
+        else:
+            self.input_missing_mask = None
         self.noisy_input = None
         self.auxinput = auxinput
         self.idx_list = T.ivector('idx_list') if not(self.auxinput is None) else None
@@ -243,6 +264,18 @@
         return self.random.binomial(T.shape(self.input), 1, 1 - self.noise_level) * self.input
     
     def reconstruction_costs(self, rec):
+        if self.ignore_missing and self.input is not None:
+            # Note: the following code is very ugly. It is just a hack to
+            # ensure that the gradient w.r.t. missing coordinates is (close to)
+            # zero. It is neither efficient nor elegant.
+            # The idea is to put a very big negative value in the
+            # reconstruction for these missing inputs (whose target is 0), so
+            # that the gradient is 1/(1 - rec) ~= 0.
+            # This will in particular screw up the cost computations.
+            zero = rec * 0
+            rec = (rec * T.neq(self.input_missing_mask, zero) +
+                    (zero - 1e100) * T.eq(self.input_missing_mask, zero))
+            
         if self.input is None:
             return self.reconstruction_cost_function(scaninputs(self.idx_list,self.auxinput), rec)
         if self.auxinput is None: