@@ -57,53 +57,57 @@ class ChunkEvalOpMaker : public framework::OpProtoAndCheckerMaker {
framework::OpAttrChecker*op_checker)
:OpProtoAndCheckerMaker(proto,op_checker){
AddInput("Inference",
"(Tensor, default: Tensor<int>) Predictions from the network.");
AddInput("Label","(Tensor, default: Tensor<int>) Labels of the data.");
AddOutput(
"Precision",
"(float) The precision ratio of the predictions on current data.");
"(Tensor, default: Tensor<int>). Predictions from the network.");
AddInput("Label",
"(Tensor, default: Tensor<int>). The true tag sequences.");
AddOutput("Precision",
"(float). The evaluated precision (called positive predictive "
"value) of chunks on the given mini-batch.");
AddOutput("Recall",
"(float) The recall ratio of the predictions on current data.");
"(float). The evaluated recall (true positive rate or "
"sensitivity) of chunks on the given mini-batch.");
AddOutput("F1-Score",
"(float) The F1-Score of the predictions on current data.");
AddAttr<int>("num_chunk_types","(int) The number of chunk type.");
AddAttr<std::string>("chunk_scheme",
"(string, default IOB) The label scheme.")
"(float). The evaluated F1-Score on the given mini-batch.");
AddAttr<int>("num_chunk_types",
"(int). The number of chunk type. See below for details.");
AddAttr<std::string>(
"chunk_scheme",
"(string, default IOB). The labeling scheme indicating "
"how to encode the chunks. Must be IOB, IOE, IOBES or plain. See below "
"for details.")
.SetDefault("IOB");
AddAttr<std::vector<int>>(
"excluded_chunk_types",
"(list<int>) A list<int> indicating chunk types not to be counted.")
AddAttr<std::vector<int>>("excluded_chunk_types",
"(list<int>) A list including chunk type ids "
"indicating chunk types that are not counted. "
"See below for details.")
.SetDefault(std::vector<int>{});
AddComment(R"DOC(
Chunk evaluator is used to evaluate segment labelling accuracy for a
sequence. It calculates precision, recall and F1 scores for the chunk detection.
To use chunk evaluator, several concepts need to be clarified firstly.
[Chunk type] is the type of the whole chunk and a chunk consists of one or several words. (For example in NER, ORG for organization name, PER for person name etc.)
[Tag type] indicates the position of a word in a chunk. (B for begin, I for inside, E for end, S for single)
We can name a label by combining tag type and chunk type. (ie. B-ORG for begining of an organization name)
The construction of label dictionary should obey the following rules:
- Use one of the listed labelling schemes. These schemes differ in ways indicating chunk boundry.
Scheme Description
plain Use the same label for the whole chunk.
IOB Two labels for chunk type X, B-X for chunk begining and I-X for chunk inside.
IOE Two labels for chunk type X, E-X for chunk ending and I-X for chunk inside.
IOBES Four labels for chunk type X, B-X for chunk begining, I-X for chunk inside, E-X for chunk end and S-X for single word chunk.
To make it clear, let's illustrate by an NER example.
Assuming that there are three named entity types including ORG, PER and LOC which are called 'chunk type' here,
if 'IOB' scheme were used, the label set will be extended to a set including B-ORG, I-ORG, B-PER, I-PER, B-LOC, I-LOC and O,
in which B-ORG for begining of ORG and I-ORG for inside of ORG.
Prefixes which are called 'tag type' here are added to chunk types and there are two tag types including B and I.
Of course, the training data should be labeled accordingly.
- Mapping is done correctly by the listed equations and assigning protocol.
The following table are equations to extract tag type and chunk type from a label.
tagType = label % numTagType
chunkType = label / numTagType
otherChunkType = numChunkTypes
The following table shows the mapping rule between tagType and tag type in each scheme.
For some basics of chunking, please refer to
‘Chunking with Support Vector Mechines <https://aclanthology.info/pdf/N/N01/N01-1025.pdf>’.
CheckEvalOp computes the precision, recall, and F1-score of chunk detection,
and supports IOB, IOE, IOBES and IO (also known as plain) tagging schemes.
Here is a NER example of labeling for these tagging schemes:
Li Ming works at Agricultural Bank of China in Beijing.
IO: I-PER I-PER O O I-ORG I-ORG I-ORG I-ORG O I-LOC
IOB: B-PER I-PER O O B-ORG I-ORG I-ORG I-ORG O B-LOC
IOE: I-PER E-PER O O I-ORG I-ORG I-ORG E-ORG O E-LOC
IOBES: B-PER E-PER O O I-ORG I-ORG I-ORG E-ORG O S-LOC
There are three chunk types(named entity types) including PER(person), ORG(orgnazation)
and LOC(LOCATION), and we can see that the labels have the form <tag type>-<chunk type>.
Since the calculations actually use label ids rather than labels, extra attention
should be paid when mapping labels to ids to make CheckEvalOp work. The key point
is that the listed equations are satisfied by ids.
tag_type = label % num_tag_type
chunk_type = label / num_tag_type
where `num_tag_type` is the num of tag types in the tagging scheme, `num_chunk_type`
is the num of chunk types, and `tag_type` get its value from the following table.
Scheme Begin Inside End Single
plain 0 - - -
...
...
@@ -111,7 +115,8 @@ The following table shows the mapping rule between tagType and tag type in each
IOE - 0 1 -
IOBES 0 1 2 3
Continue the NER example, and the label dict should look like this to satify above equations:
Still use NER as example, assuming the tagging scheme is IOB while chunk types are ORG,
PER and LOC. To satisfy the above equations, the label map can be like this:
B-ORG 0
I-ORG 1
...
...
@@ -121,11 +126,10 @@ Continue the NER example, and the label dict should look like this to satify abo
I-LOC 5
O 6
In this example, chunkType has three values: 0 for ORG, 1 for PER, 2 for LOC, because the scheme is
"IOB" so tagType has two values: 0 for B and 1 for I.
Here we will use I-LOC to explain the above mapping rules in detail.
For I-LOC, the label id is 5, so we can get tagType=1 and chunkType=2, which means I-LOC is a part of NER chunk LOC
and the tag is I.
It’s not hard to verify the equations noting that the num of chunk types
is 3 and the num of tag types in IOB scheme is 2. For example, the label
id of I-LOC is 5, the tag type id of I-LOC is 1, and the chunk type id of
I-LOC is 2, which consistent with the results from the equations.
