Merge pull request #39324 from pvarouktsis:master

PiperOrigin-RevId: 373627910
Change-Id: Ic7defb871fec22ff189b2e0b6c39258efd349184

tensorflow/core/kernels/ctc_decoder_ops.cc

@@ -187,6 +187,7 @@ class CTCGreedyDecoderOp : public OpKernel {
  public:
   explicit CTCGreedyDecoderOp(OpKernelConstruction* ctx) : OpKernel(ctx) {
     OP_REQUIRES_OK(ctx, ctx->GetAttr("merge_repeated", &merge_repeated_));
+    OP_REQUIRES_OK(ctx, ctx->GetAttr("blank_index", &blank_index_));
   }
 
   void Compute(OpKernelContext* ctx) override {
@@ -223,8 +224,12 @@ class CTCGreedyDecoderOp : public OpKernel {
 
     log_prob_t.setZero();
 
-    // Assumption: the blank index is num_classes - 1
-    int blank_index = num_classes - 1;
+    int blank_index =
+        (blank_index_ < 0) ? num_classes + blank_index_ : blank_index_;
+    OP_REQUIRES(ctx, FastBoundsCheck(blank_index, num_classes),
+                errors::InvalidArgument("blank_index expected to be between ",
+                                        -num_classes, " and ", num_classes - 1,
+                                        " but was ", blank_index_));
 
     // Perform best path decoding
     std::vector<std::vector<std::vector<int> > > sequences(batch_size);
@@ -263,6 +268,7 @@ class CTCGreedyDecoderOp : public OpKernel {
  private:
   CTCDecodeHelper decode_helper_;
   bool merge_repeated_;
+  int blank_index_;
 
   TF_DISALLOW_COPY_AND_ASSIGN(CTCGreedyDecoderOp);
 };

tensorflow/core/ops/ctc_ops.cc

@@ -103,6 +103,7 @@ REGISTER_OP("CTCGreedyDecoder")
     .Input("inputs: T")
     .Input("sequence_length: int32")
     .Attr("merge_repeated: bool = false")
+    .Attr("blank_index: int = -1")
     .Output("decoded_indices: int64")
     .Output("decoded_values: int64")
     .Output("decoded_shape: int64")

tensorflow/python/kernel_tests/ctc_decoder_ops_test.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # ==============================================================================
-"""Tests for tensorflow.ctc_ops.ctc_loss_op."""
+"""Tests for tensorflow.ctc_ops.ctc_decoder_ops."""
 
 from __future__ import absolute_import
 from __future__ import division
@@ -100,39 +100,39 @@ def testCTCGreedyDecoder(self):
     """Test two batch entries - best path decoder."""
     max_time_steps = 6
     # depth == 4
-
     seq_len_0 = 4
     input_prob_matrix_0 = np.asarray(
-        [[1.0, 0.0, 0.0, 0.0],  # t=0
-         [0.0, 0.0, 0.4, 0.6],  # t=1
-         [0.0, 0.0, 0.4, 0.6],  # t=2
-         [0.0, 0.9, 0.1, 0.0],  # t=3
-         [0.0, 0.0, 0.0, 0.0],  # t=4 (ignored)
-         [0.0, 0.0, 0.0, 0.0]],  # t=5 (ignored)
+        [
+            [1.0, 0.0, 0.0, 0.0],  # t=0
+            [0.0, 0.0, 0.4, 0.6],  # t=1
+            [0.0, 0.0, 0.4, 0.6],  # t=2
+            [0.0, 0.9, 0.1, 0.0],  # t=3
+            [0.0, 0.0, 0.0, 0.0],  # t=4 (ignored)
+            [0.0, 0.0, 0.0, 0.0]
+        ],  # t=5 (ignored)
         dtype=np.float32)
     input_log_prob_matrix_0 = np.log(input_prob_matrix_0)
 
     seq_len_1 = 5
     # dimensions are time x depth
-
     input_prob_matrix_1 = np.asarray(
         [
             [0.1, 0.9, 0.0, 0.0],  # t=0
             [0.0, 0.9, 0.1, 0.0],  # t=1
             [0.0, 0.0, 0.1, 0.9],  # t=2
             [0.0, 0.9, 0.1, 0.1],  # t=3
             [0.9, 0.1, 0.0, 0.0],  # t=4
-            [0.0, 0.0, 0.0, 0.0]
-        ],  # t=5 (ignored)
+            [0.0, 0.0, 0.0, 0.0]  # t=5 (ignored)
+        ],
         dtype=np.float32)
     input_log_prob_matrix_1 = np.log(input_prob_matrix_1)
 
     # len max_time_steps array of batch_size x depth matrices
-    inputs = [
+    inputs = np.array([
         np.vstack(
             [input_log_prob_matrix_0[t, :], input_log_prob_matrix_1[t, :]])
         for t in range(max_time_steps)
-    ]
+    ])
 
     # batch_size length vector of sequence_lengths
     seq_lens = np.array([seq_len_0, seq_len_1], dtype=np.int32)
@@ -157,21 +157,46 @@ def testCTCGreedyDecoder(self):
                 dtype=np.int64),
             np.array(
                 [
-                    0,
-                    1,  # batch 0
+                    0,  # batch 0, 2 values
                     1,
+                    1,  # batch 1, 3 values
                     1,
                     0
-                ],  # batch 1
+                ],
                 dtype=np.int64),
             # shape is batch x max_decoded_length
-            np.array(
-                [2, 3], dtype=np.int64)),
+            np.array([2, 3], dtype=np.int64)),
     ]
 
+    # Test without defining blank_index
     self._testCTCDecoder(ctc_ops.ctc_greedy_decoder, inputs, seq_lens,
                          log_prob_truth, decode_truth)
 
+    # Shift blank_index to be somewhere in the middle of inputs
+    blank_index = 2
+    inputs = np.concatenate(
+        (inputs[:, :, :blank_index], inputs[:, :, -1:], inputs[:, :,
+                                                               blank_index:-1]),
+        axis=2)
+
+    # Test positive value in blank_index
+    self._testCTCDecoder(
+        ctc_ops.ctc_greedy_decoder,
+        inputs,
+        seq_lens,
+        log_prob_truth,
+        decode_truth,
+        blank_index=2)
+
+    # Test negative value in blank_index
+    self._testCTCDecoder(
+        ctc_ops.ctc_greedy_decoder,
+        inputs,
+        seq_lens,
+        log_prob_truth,
+        decode_truth,
+        blank_index=-2)
+
   @test_util.run_deprecated_v1
   def testCTCDecoderBeamSearch(self):
     """Test one batch, two beams - hibernating beam search."""

tensorflow/python/kernel_tests/ctc_loss_op_test.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 # ==============================================================================
-"""Tests for tensorflow.ctc_ops.ctc_decoder_ops."""
+"""Tests for tensorflow.ctc_ops.ctc_loss_op."""
 
 from __future__ import absolute_import
 from __future__ import division

tensorflow/python/ops/ctc_ops.py

@@ -287,12 +287,38 @@ def _CTCLossV2Grad(op, grad_loss, _):
 
 @tf_export("nn.ctc_greedy_decoder")
 @dispatch.add_dispatch_support
-def ctc_greedy_decoder(inputs, sequence_length, merge_repeated=True):
+def ctc_greedy_decoder(inputs,
+                       sequence_length,
+                       merge_repeated=True,
+                       blank_index=None):
   """Performs greedy decoding on the logits given in input (best path).
 
-  Note: Regardless of the value of merge_repeated, if the maximum index of a
-  given time and batch corresponds to the blank index `(num_classes - 1)`, no
-  new element is emitted.
+  Given a tensor as `inputs`, the `blank_index` parameter defines the class
+  index of the blank symbol.
+
+  For example:
+
+  If `blank_index` is equal to 1:
+
+  >>> inf = float("inf")
+  >>> logits = tf.constant([[[   0., -inf, -inf],
+  ...                        [ -2.3, -inf, -0.1]],
+  ...                       [[ -inf, -0.5, -inf],
+  ...                        [ -inf, -inf, -0.1]],
+  ...                       [[ -inf, -inf, -inf],
+  ...                        [ -0.1, -inf, -2.3]]])
+  >>> seq_lens = tf.constant([2, 3])
+  >>> outputs = tf.nn.ctc_greedy_decoder(
+  ...     logits,
+  ...     seq_lens,
+  ...     blank_index=1)
+
+  Notes:
+
+  - Regardless of the value of `merge_repeated`, if an index of a
+    given time and batch corresponds to the `blank_index`, no new
+    element is emitted.
+  - Default `blank_index` is `(num_classes - 1)`, unless overriden.
 
   If `merge_repeated` is `True`, merge repeated classes in output.
   This means that if consecutive logits' maximum indices are the same,
@@ -308,6 +334,10 @@ def ctc_greedy_decoder(inputs, sequence_length, merge_repeated=True):
     sequence_length: 1-D `int32` vector containing sequence lengths, having size
       `[batch_size]`.
     merge_repeated: Boolean.  Default: True.
+    blank_index: (Optional). Default: `num_classes - 1`. Define the class index
+      to use for the blank label. Negative values will start from num_classes,
+      ie, -1 will reproduce the ctc_greedy_decoder behavior of using
+      num_classes - 1 for the blank symbol, which corresponds to the default.
 
   Returns:
     A tuple `(decoded, neg_sum_logits)` where
@@ -328,8 +358,12 @@ def ctc_greedy_decoder(inputs, sequence_length, merge_repeated=True):
         sequence found, the negative of the sum of the greatest logit at each
         timeframe.
   """
+
   outputs = gen_ctc_ops.ctc_greedy_decoder(
-      inputs, sequence_length, merge_repeated=merge_repeated)
+      inputs,
+      sequence_length,
+      merge_repeated=merge_repeated,
+      blank_index=blank_index)
   (decoded_ix, decoded_val, decoded_shape, log_probabilities) = outputs
   return ([sparse_tensor.SparseTensor(decoded_ix, decoded_val,
                                       decoded_shape)], log_probabilities)

tensorflow/tools/api/golden/v1/tensorflow.nn.pbtxt

@@ -126,7 +126,7 @@ tf_module {
   }
   member_method {
     name: "ctc_greedy_decoder"
-    argspec: "args=[\'inputs\', \'sequence_length\', \'merge_repeated\'], varargs=None, keywords=None, defaults=[\'True\'], "
+    argspec: "args=[\'inputs\', \'sequence_length\', \'merge_repeated\', \'blank_index\'], varargs=None, keywords=None, defaults=[\'True\', \'None\'], "
   }
   member_method {
     name: "ctc_loss"

tensorflow/tools/api/golden/v1/tensorflow.raw_ops.pbtxt

@@ -690,7 +690,7 @@ tf_module {
   }
   member_method {
     name: "CTCGreedyDecoder"
-    argspec: "args=[\'inputs\', \'sequence_length\', \'merge_repeated\', \'name\'], varargs=None, keywords=None, defaults=[\'False\', \'None\'], "
+    argspec: "args=[\'inputs\', \'sequence_length\', \'merge_repeated\', \'blank_index\', \'name\'], varargs=None, keywords=None, defaults=[\'False\', \'-1\', \'None\'], "
   }
   member_method {
     name: "CTCLoss"

tensorflow/tools/api/golden/v2/tensorflow.nn.pbtxt

@@ -106,7 +106,7 @@ tf_module {
   }
   member_method {
     name: "ctc_greedy_decoder"
-    argspec: "args=[\'inputs\', \'sequence_length\', \'merge_repeated\'], varargs=None, keywords=None, defaults=[\'True\'], "
+    argspec: "args=[\'inputs\', \'sequence_length\', \'merge_repeated\', \'blank_index\'], varargs=None, keywords=None, defaults=[\'True\', \'None\'], "
   }
   member_method {
     name: "ctc_loss"

tensorflow/tools/api/golden/v2/tensorflow.raw_ops.pbtxt

@@ -690,7 +690,7 @@ tf_module {
   }
   member_method {
     name: "CTCGreedyDecoder"
-    argspec: "args=[\'inputs\', \'sequence_length\', \'merge_repeated\', \'name\'], varargs=None, keywords=None, defaults=[\'False\', \'None\'], "
+    argspec: "args=[\'inputs\', \'sequence_length\', \'merge_repeated\', \'blank_index\', \'name\'], varargs=None, keywords=None, defaults=[\'False\', \'-1\', \'None\'], "
   }
   member_method {
     name: "CTCLoss"