Merge pull request #10 from LdDl/embedding-layer

implement embedding layer

cmd/examples/train_embedding/README.md

@@ -0,0 +1,152 @@
+# Example of how to use Embedding layers
+
+Let's imagine that we have need to do following task:
+
+    Convert the textual assessment of the quality of the work into a numerical grade.
+
+    If work is not done (or is done in a bad way) then assessment is 0.0
+
+    If work is done (and is done in a good way) then assessment is 1.0
+
+    If work is done in a mediocre way then assessment is 0.5
+
+Examples of input data (with corresponding assessment):
+```
+Well done! - 1.0
+Good work - 1.0
+Great effort - 1.0
+nice work - 1.0
+Excellent! - 1.0
+Weak - 0.0
+Poor effort! - 0.0
+not good - 0.0
+poor work - 0.0
+Could be way better. - 0.0
+average :( - 0.5
+middle level - 0.5
+ordinary stuff - 0.5
+boilerplate - 0.5
+standart approach - 0.5
+```
+
+Restrictions:
+* Assume that vocabulary size is 50
+* Max amount of words in a text assesment 5
+
+So, neural network structure would be:
+* Input shape equals to {**1** x **Max number of words in a sentence**}. Max number of words is defined as "5"
+* Output shape equals to {**1** x **1**} since there is only one possible output (0.0, 1.0 or 0.5 in perfect conditions)
+* Layers:
+    * Embedding layer - Let's assume embedding dimensions is 12.
+
+        It means that this layer has **Vocabulary size (which is 50)**-tensor of size **embedding dimensions (which is 12)**.
+
+        No activation function is required. No bias is required.
+    * Flatten layer - just represent N-tensor as [**1** x **Total number of elements in tensor**]
+    * Output layer - just linear layer with sigmoid activation function.
+
+        Number of input neurons: [**Max number of words in a sentence** x **Embedding dimensions**]. Number of output neurons: [**1** x **1**]
+
+        No bias is required. 
+* How to represent text as numerical data? Well, [HashingTrick](../../../utils.go#L313) and [PaddingInt64Slice](../../../utils.go#L288) will help to do this task
+
+Final representation of network:
+input(1, 5) -> embedding(inputs=5, voc=50, dims=12) -> flatten(5,12) -> linear(inputs=60, outputs=1) -> sigmoid(1)
+
+Assume that number of training epochs is 200, learning rate is 0.01, solver is Adam, batch size is 1
+
+Main code is in [main.go file](main.go). I guess it's pretty straightforward. But if it's not than I appreciate yours PR to improve this document
+
+Simply execute:
+```shell
+go run main.go
+```
+
+Final output on for trainig data (may vary due the nature of rand() calls):
+```shell
+Epoch 0:
+        Discriminator's loss: 0.0016569854606968827
+Epoch 40:
+        Discriminator's loss: 0.04548602801653217
+Epoch 80:
+        Discriminator's loss: 0.0034698363241729554
+Epoch 120:
+        Discriminator's loss: 0.007486103427248882
+Epoch 160:
+        Discriminator's loss: 9.23967546782277e-05
+Text assessment: Weak
+        Its hashed value: [5 0 0 0 0]
+        Its defined numerical assessment: 0.0
+        Its evaluated numerical assessment: 0.0
+        Difference between defined and evaluated: 0.0
+Text assessment: middle level
+        Its hashed value: [12 40 0 0 0]
+        Its defined numerical assessment: 0.5
+        Its evaluated numerical assessment: 0.5
+        Difference between defined and evaluated: 0.0
+Text assessment: not good
+        Its hashed value: [31 14 0 0 0]
+        Its defined numerical assessment: 0.0
+        Its evaluated numerical assessment: 0.0
+        Difference between defined and evaluated: 0.0
+Text assessment: Good work
+        Its hashed value: [14 24 0 0 0]
+        Its defined numerical assessment: 1.0
+        Its evaluated numerical assessment: 0.9
+        Difference between defined and evaluated: 0.1
+Text assessment: ordinary stuff
+        Its hashed value: [23 44 0 0 0]
+        Its defined numerical assessment: 0.5
+        Its evaluated numerical assessment: 0.5
+        Difference between defined and evaluated: 0.0
+Text assessment: Could be way better.
+        Its hashed value: [36 25 5 18 0]
+        Its defined numerical assessment: 0.0
+        Its evaluated numerical assessment: 0.0
+        Difference between defined and evaluated: 0.0
+Text assessment: average :(
+        Its hashed value: [35 41 0 0 0]
+        Its defined numerical assessment: 0.5
+        Its evaluated numerical assessment: 0.5
+        Difference between defined and evaluated: 0.0
+Text assessment: Great effort
+        Its hashed value: [26 11 0 0 0]
+        Its defined numerical assessment: 1.0
+        Its evaluated numerical assessment: 0.9
+        Difference between defined and evaluated: 0.1
+Text assessment: poor work
+        Its hashed value: [28 24 0 0 0]
+        Its defined numerical assessment: 0.0
+        Its evaluated numerical assessment: 0.1
+        Difference between defined and evaluated: 0.1
+Text assessment: boilerplate
+        Its hashed value: [36 0 0 0 0]
+        Its defined numerical assessment: 0.5
+        Its evaluated numerical assessment: 0.5
+        Difference between defined and evaluated: 0.0
+Text assessment: standart approach
+        Its hashed value: [13 29 0 0 0]
+        Its defined numerical assessment: 0.5
+        Its evaluated numerical assessment: 0.5
+        Difference between defined and evaluated: 0.0
+Text assessment: Poor effort!
+        Its hashed value: [28 11 0 0 0]
+        Its defined numerical assessment: 0.0
+        Its evaluated numerical assessment: 0.0
+        Difference between defined and evaluated: 0.0
+Text assessment: Excellent!
+        Its hashed value: [26 0 0 0 0]
+        Its defined numerical assessment: 1.0
+        Its evaluated numerical assessment: 1.0
+        Difference between defined and evaluated: 0.0
+Text assessment: nice work
+        Its hashed value: [34 24 0 0 0]
+        Its defined numerical assessment: 1.0
+        Its evaluated numerical assessment: 0.9
+        Difference between defined and evaluated: 0.1
+Text assessment: Well done!
+        Its hashed value: [26 13 0 0 0]
+        Its defined numerical assessment: 1.0
+        Its evaluated numerical assessment: 1.0
+        Difference between defined and evaluated: 0.0
+```