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two_byte_alphas.c File Reference

represent a floating point with a 2-byte integer. More...

#include <math.h>
#include "ngram.h"

Go to the source code of this file.

Functions
unsigned short	short_alpha (double long_alpha, double *alpha_array, unsigned short *size_of_alpha_array, int elements_in_range, double min_range, double max_range)
double	double_alpha (unsigned short short_alpha, double *alpha_array, int size_of_alpha_array, int elements_in_range, double min_range, double max_range)

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Detailed Description

represent a floating point with a 2-byte integer.

Each of the integers 0 ... 65535 are associated with a floating point number. For the lower integers, the floating point numbers with which they are associated are equally log-linearly spaced across the range specified by the -min_alpha and -max_alpha values (note that these values correspond to the log to the base 10 of the backoff weights). The last N integers (where N is specified by the -out_of_range_alphas switch) correspond exactly to values of alpha which are encountered which fall outside this range. Therefore, a small range with a small value of N will allow the alphas to be represented most accurately, but if more than N out of range alphas are encountered, then the program will fail. The default values are min_alpha = -3.2, max_alpha, max_alpha = 2.5, out_of_range_alphaa = 10000. This method does, however, introduce slight inaccuracies, and so it is only recommended when memory is short. By default, the alphas are stored in four bytes.

Definition in file two_byte_alphas.c.

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Function Documentation

double double_alpha (  unsigned short    short_alpha, double *    alpha_array, int    size_of_alpha_array, int    elements_in_range, double    min_range, double    max_range )

Definition at line 95 of file two_byte_alphas.c. References quit(), and short_alpha(). Referenced by bo_ng_prob(), and for().

unsigned short short_alpha (  double    long_alpha, double *    alpha_array, unsigned short *    size_of_alpha_array, int    elements_in_range, double    min_range, double    max_range )

Definition at line 46 of file two_byte_alphas.c. References i, and quit(). Referenced by compute_back_off(), and double_alpha().

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