Add Conditional Random Field (CRF) layer

tensorflow_addons/layers/BUILD

@@ -6,6 +6,7 @@ py_library(
     name = "layers",
     srcs = [
         "__init__.py",
+        "crf.py",
         "gelu.py",
         "maxout.py",
         "normalizations.py",
@@ -20,6 +21,7 @@ py_library(
     srcs_version = "PY2AND3",
     deps = [
         "//tensorflow_addons/activations",
+        "//tensorflow_addons/text",
         "//tensorflow_addons/utils",
     ],
 )
@@ -101,3 +103,16 @@ py_test(
         ":layers",
     ],
 )
+
+py_test(
+    name = "crf_test",
+    size = "small",
+    srcs = [
+        "crf_test.py",
+    ],
+    main = "crf_test.py",
+    srcs_version = "PY2AND3",
+    deps = [
+        ":layers",
+    ],
+)

tensorflow_addons/layers/README.md

@@ -3,6 +3,7 @@
 ## Maintainers
 | Submodule  |  Maintainers  | Contact Info   |
 |:---------- |:----------- |:------------- |
+| crf | @howl-anderson | u1mail2me@gmail.com |
 | gelu       | @AakashKumarNain | aakashnain@outlook.com |  
 | maxout | @fsx950223 | fsx950223@gmail.com |
 | normalizations | @smokrow | moritz.kroeger@tu-dortmund.de |
@@ -14,6 +15,7 @@
 ## Components
 | Submodule  | Layer |  Reference  |
 |:---------- |:----------- |:------------- |
+| crf | CRF | https://en.wikipedia.org/wiki/Conditional_random_field |
 | gelu   | GeLU   | https://arxiv.org/abs/1606.08415 | 
 | maxout | Maxout | https://arxiv.org/abs/1302.4389    |
 | normalizations | GroupNormalization | https://arxiv.org/abs/1803.08494 |

tensorflow_addons/layers/__init__.py

@@ -25,4 +25,5 @@
 from tensorflow_addons.layers.optical_flow import CorrelationCost
 from tensorflow_addons.layers.poincare import PoincareNormalize
 from tensorflow_addons.layers.sparsemax import Sparsemax
-from tensorflow_addons.layers.wrappers import WeightNormalization
+from tensorflow_addons.layers.wrappers import WeightNormalization
+from tensorflow_addons.layers.crf import CRF