Tuning parameters to make the ERG and ACE parse the way you want them to

This page lists some of the most useful knobs that can be used to adjust ACE's processing, and gives suggestions for how to set them for different use cases, especially with the ERG.

The three competing desiderata of precision, robustness and efficiency each demand some sacrifices from the other two. The primary control levels are:






Number of seconds to try a given input before giving up.



Number of megabytes of RAM to expend on building a forest before giving up.



Number of megabytes of RAM to expend on unpacking a forest before giving up, including RAM spend on the forest.



Enables UT. Lexical hypotheses of probability lower than X are discarded.



Enables PCFG-guided robustness. X is the path to a PCFG model.


Maximize resource limits, avoid ubertagging and robustness measures. The default settings are good as long as inputs are not too long. For complex data, try increasing the RAM limits. To avoid receiving low-ranked results from partially complete forests, make the chart and unpack megabytes identical. For example:

  • ace ... --max-chart-megabytes=8000 --max-unpack-megabytes=8000


Maximize resource limits, setting the unpack megabytes somewhat higher than the chart megabytes.

  • ace ... --max-chart-megabytes=8000 --max-unpack-megabytes=8500

Consider enabling PCFG-based guidance.

  • ace ... --pcfg=..../erg-2018/etc/all-treebanks-gp0-2018.pcfg
    • OR
    gunzip ..../erg-2018/etc/ww-gp2-2018.pcfg.gz ace ... --pcfg=..../erg-2018/etc/ww-gp2-2018.pcfg

If resources are not unlimited, enable UT. A threshold of 0.00001 typically doesn't sacrifice too much coverage or precision but reduces resource consumption considerably.

  • ace ... --ut=0.00001

The above measures can be used separately or in combination. See below for a discussion of additional strategies.


Set aggressive resource limits and a higher UT threshold. If PCFG guidance is used, use the smaller (all-treebanks-gp0-2018.pcfg) model.

  • ace ... --ut=0.01 --timeout=10
    • OR
    ace ... --ut=0.01 --timeout=10 --pcfg=..../erg-2018/etc/all-treebanks-gp0-2018.pcfg

Additional Robustness Measures

There are a few additional techniques available for increasing coverage at the expense of efficiency and precision. These may be of use to some users.


Compile the grammar using erg-2018/ace/config-educ.tdl instead of erg-2018/ace/config.tdl. This enables a collection of additional rules which allow the grammar to natively analyse a variety of mildly ungrammatical structures such as subject-verb number mismatch and missing determiners.

  • ace -G erg-2018.dat -g ..../erg-2018/ace/config-educ.tdl

AceErgTuning (last edited 2018-11-19 22:55:05 by WoodleyPackard)

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