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Refine comment for CRF related headers. #117

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Sep 26, 2016
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2 changes: 1 addition & 1 deletion paddle/gserver/layers/CRFLayer.h
Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,7 @@ namespace paddle {
/**
* A layer for calculating the cost of sequential conditional random field
* model.
* See LinearChainCRF.h for the detail of the CRF formulation.
* See class LinearChainCRF for the detail of the CRF formulation.
*/
class CRFLayer : public Layer {
public:
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48 changes: 24 additions & 24 deletions paddle/gserver/layers/LinearChainCRF.h
Original file line number Diff line number Diff line change
Expand Up @@ -21,39 +21,39 @@ namespace paddle {

class LinearChainCRF {
public:
/*
The size of para and grad must be (numClasses + 2) * numClasses.
The first numClasses values of para are for starting weights (a).
The next numClasses values of para are for ending weights (b),
The remaning values are for transition weights (w).

The probability of a state sequence s of length L is defined as:
P(s) = (1/Z) exp(a_{s_1} + b_{s_L}
+ \sum_{l=1}^L x_{s_l}
+ \sum_{l=2}^L w_{s_{l-1},s_l})
where Z is a normalization value so that the sum of P(s) over all possible
sequences is 1, and x is the input feature to the CRF.
/**
* The size of para and grad must be \f$(numClasses + 2) * numClasses\f$.
* The first numClasses values of para are for starting weights (\f$a\f$).
* The next numClasses values of para are for ending weights (\f$b\f$),
* The remaning values are for transition weights (\f$w\f$).
*
* The probability of a state sequence s of length \f$L\f$ is defined as:
* \f$P(s) = (1/Z) exp(a_{s_1} + b_{s_L}
* + \sum_{l=1}^L x_{s_l}
* + \sum_{l=2}^L w_{s_{l-1},s_l})\f$
* where \f$Z\f$ is a normalization value so that the sum of \f$P(s)\f$ over all possible
* sequences is \f$1\f$, and \f$x\f$ is the input feature to the CRF.
*/
LinearChainCRF(int numClasses, real* para, real* grad);

/*
Calculate the negative log likelihood of s given x.
The size of x must be length * numClasses. Each consecutive numClasses
values are the features for one time step.
/**
* Calculate the negative log likelihood of s given x.
* The size of x must be length * numClasses. Each consecutive numClasses
* values are the features for one time step.
*/
real forward(real* x, int* s, int length);

/*
Calculate the gradient with respect to x, a, b, and w.
The gradient of x will be stored in dx.
backward() can only be called after a corresponding call to forward() with
the same x, s and length.
NOTE: The gradient is added to dx and grad (provided at constructor).
/**
* Calculate the gradient with respect to x, a, b, and w.
* The gradient of x will be stored in dx.
* backward() can only be called after a corresponding call to forward() with
* the same x, s and length.
* @note The gradient is added to dx and grad (provided at constructor).
*/
void backward(real* x, real* dx, int* s, int length);

/*
Find the most probable sequence given x. The result will be stored in s.
/**
* Find the most probable sequence given x. The result will be stored in s.
*/
void decode(real* x, int* s, int length);

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