Recurrent Neural Network Grammars
Table 7: PTB and CTB language modeling results including results with the buggy composition function implementation (indicated by †) and with the correct implementation.
['[BOLD] Model', '[BOLD] test ppl (PTB)', '[BOLD] test ppl (CTB)']
The implementation error affected both the generative and discriminative RNNGs. The considerable improvement in parsing accuracy indicates that properly composing the constituent and propagating information upwards is crucial. Despite slightly higher language modeling perplexity on PTB §23, the fixed RNNG still outperforms a highly optimized sequential LSTM baseline.