twitter 㧠@takeda25 ãããææããã¦ããã®ã§ãã, CRF 㧠f(y_{i-1},y_{i},x_{i}) ã¨ããè¦³æ¸¬ç´ æ§ã¨ã©ãã« bigram ã®çµã¿ã¾ã§èæ ®ããç´ æ§é¢æ°ããã¾ã使ãããªãã®ã¯, ç´ æ§æ°ãå¢ããããã¨ããããã¯è¨ç®ã«æéãæããããã ããã? ã¨ããäºãç§ãªãã«èãã¦ã¿ã¾ãã. CRF ã®1äºä¾ã«å¯¾ãããã©ã¡ã¼ã¿æ¨å®ã«æãããªã¼ãã¼ã¯ã©ãã«æ°L, ç³»åé·Tã®æã«, O(L^2T) ã§ã. forward-backward ã§ã©ãã£ã¹ä¸ã®ä½ç½® i, ã©ãã« j ã®ãã¼ãã® alpha ãè¨ç®ããéã«ã¯ä»¥ä¸ã® logsumexp ã®è¨ç®ãè¡ãã¾ã. for (k = 0; k < L; ++k) alpha_{i,j} = logsumexp(alpha_{i,j}, alpha_{i-1,k}+cost) ãã®è¨ç®ãå ¨ã¦ã® i, j ã«ã¤ãã¦è¡ãã¾ã.
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