混合ガウス分布計算: Gaussian pruning (beam algorithm) [詳細]

#include <sent/stddefs.h>
#include <sent/htk_hmm.h>
#include <sent/htk_param.h>
#include <sent/hmm.h>
#include <sent/hmm_calc.h>

関数
static void	clear_dimthres (HMMWork *wrk)
	Clear per-dimension thresholds.
static void	set_dimthres (HMMWork *wrk)
	Set beam thresholds by adding TMBEAMWIDTH to the maximum values of each dimension.
static LOGPROB	compute_g_beam_updating (HMMWork wrk, HTK_HMM_Dens binfo)
	Calculate probability with threshold update.
static LOGPROB	compute_g_beam_pruning (HMMWork wrk, HTK_HMM_Dens binfo)
	Calculate probability with pruning.
boolean	gprune_beam_init (HMMWork *wrk)
	Initialize and setup work area for Gaussian pruning by beam algorithm.
void	gprune_beam_free (HMMWork *wrk)
	Free gprune_beam related work area.
void	gprune_beam (HMMWork wrk, HTK_HMM_Dens g, int gnum, int last_id, int lnum)
	Compute a set of Gaussians with beam pruning.

説明

混合ガウス分布計算: Gaussian pruning (beam algorithm)

gprune_beam()は混合ガウス分布集合の計算ルーチンの一つです． beam pruning を使って上位のガウス分布の出力確率のみを高速に求めます． Tied-mixture HMM 使用時に Julius でGPRUNE_DEFAULT_BEAM が定義されているか，あるいはJuliusのオプション "-gprune beam" を指定することでこの関数が使用されます．

beam pruning は最も積極的に枝刈りを行ないます．計算は最も高速ですが，上位のガウス分布が正しく得られず出力確率の誤りが大きくなる可能性があります．

gprune_beam() は outprob_init() によってその関数へのポインタが compute_gaussset にセットされることで使用されます．このポインタが calc_tied_mix() または calc_mix() から呼び出されます．

作者:: Akinobu LEE

日付:: Thu Feb 17 03:27:53 2005

Revision:: 1.5

gprune_beam.c で定義されています。

関数

static void clear_dimthres ( HMMWork * wrk ) [static]

Clear per-dimension thresholds.

引数:

wrk	[i/o] HMM computation work area

gprune_beam.c の 125 行で定義されています。

参照元 gprune_beam().

static void set_dimthres ( HMMWork * wrk ) [static]

Set beam thresholds by adding TMBEAMWIDTH to the maximum values of each dimension.

引数:

wrk	[i/o] HMM computation work area

gprune_beam.c の 139 行で定義されています。

参照元 gprune_beam().

static LOGPROB compute_g_beam_updating	(	HMMWork *	wrk,
		HTK_HMM_Dens *	binfo
	)		`[static]`

Calculate probability with threshold update.

Calculate probability of a Gaussian toward OP_vec, while storing the maximum values of each dimension to dimthres. for future pruning. The pruning itself is not performed here. This function will be used to compute the first N Gaussians.

引数:

wrk	[i/o] HMM computation work area
binfo	[in] Gaussian density

戻り値:: the output log probability.

gprune_beam.c の 159 行で定義されています。

参照元 gprune_beam().

static LOGPROB compute_g_beam_pruning	(	HMMWork *	wrk,
		HTK_HMM_Dens *	binfo
	)		`[static]`

Calculate probability with pruning.

Calculate probability of a Gaussian toward OP_vec, performing pruning using the dimension thresholds that has been set by compute_g_beam_updating() and set_dimthres().

引数:

wrk	[i/o] HMM computation work area
binfo	[in] Gaussian density

戻り値:: the output log probability.

gprune_beam.c の 199 行で定義されています。

参照元 gprune_beam().

boolean gprune_beam_init ( HMMWork * wrk )

Initialize and setup work area for Gaussian pruning by beam algorithm.

引数:

wrk	[i/o] HMM computation work area

戻り値:: TRUE on success, FALSE on failure.

gprune_beam.c の 234 行で定義されています。

参照元 outprob_init().

void gprune_beam_free ( HMMWork * wrk )

Free gprune_beam related work area.

引数:

wrk	[i/o] HMM computation work area

gprune_beam.c の 257 行で定義されています。

参照元 outprob_init().

void gprune_beam	(	HMMWork *	wrk,
		HTK_HMM_Dens **	g,
		int	gnum,
		int *	last_id,
		int	lnum
	)

Compute a set of Gaussians with beam pruning.

If the N-best mixtures in the previous frame is specified in last_id, They are first computed to set the thresholds for each dimension. After that, the rest of the Gaussians will be computed with those dimension thresholds to drop unpromising Gaussians from computation at early stage of likelihood computation. If the last_id is not specified (typically at the first frame of the input), a safe pruning as same as one in gprune_safe.c will be applied.

The calculated scores will be stored to OP_calced_score, with its corresponding mixture id to OP_calced_id. These are done by calling cache_push(). The number of calculated mixtures is also stored in OP_calced_num.

This can be called from calc_tied_mix() or calc_mix().

引数:

wrk	[i/o] HMM computation work area
g	[in] set of Gaussian densities to compute the output probability
gnum	[in] length of above
last_id	[in] ID list of N-best mixture in previous input frame, or NULL if not exist
lnum	[in] length of last_id

gprune_beam.c の 291 行で定義されています。

参照元 outprob_init().