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@@ -83,12 +83,91 @@ generated files created with other optimization flags.
<p> <p>
<b>Notice</b>: If you use the <b>Important notice</b>: If you use the
<a href="http://www.cs.chalmers.se/~bringert/gf/gf-java.html"> <a href="http://www.cs.chalmers.se/~bringert/gf/gf-java.html">
Embedded GF Interpreter</a>, only the values <tt>none</tt> and Embedded GF Interpreter</a>,
<tt>share</tt> can be used; the stronger optimizations are not or the improved parsing algorithms described below,
only the values <tt>none</tt>,
<tt>share</tt> and <tt>values</tt> can be used; the stronger optimizations are not
supported yet. supported yet.
Also note that currently, GF aborts and reports an error if the stronger optimizations are used
when creating the grammar for the Embedded GF Interpreter, or when trying to parse.
<h3>Improved parsing algorithms</h3>
We have implemented some of the suggested parsing algorithms described in
Peter Ljunglöf's <a href="http://www.cs.chalmers.se/~peb/pubs.html">PhD thesis</a>.
So now there are the following options for parsing:
<ul>
<li>The default parser. It uses a (possibly) very overgenerating context-free grammar, and filters the resulting parse trees by type-checking.
<li>The <tt>-cfg</tt> flag. It uses a much less overgenerating context-free grammar, and filters as above.
<li>The <tt>-mcfg</tt> flag. It uses an even less overgenerating <em>multiple context-free grammar</em>.
If the abstract syntax is context-free, meaning that there are no dependent types and only first-order functions,
the trees do not have to be filtered at all.
</ul>
The option <tt>-parser=X</tt> selects the parsing strategy. The default parser has the strategies
<tt>chart</tt>, <tt>bottomup</tt>, <tt>topdown</tt>, <tt>old</tt>, with the first one being the default.
The <tt>-cfg</tt> and <tt>-mcfg</tt> parsers only recognize the <tt>bottomup</tt> and <tt>topdown</tt> strategies.
<p>
<b>Note</b> that the <tt>-cfg</tt> and <tt>-mcfg</tt> parsers can take a very long time on their first call, since
they have to convert the GF grammar. This will only happen once in a GF run, provided the GF files are not changed.
<p>
<b>Tips</b> for choosing the best parser for your grammar. Try with the default parser; if it is too slow, try the other two.
Remember that the first time you parse they will be very slow, since they have to build parsing information.
the <tt>-cfg</tt> parser is best on grammars with many parameters and inflection tables, and
The <tt>-mcfg</tt> parser is even better when the grammar also has discontinuous constituents.
<p>
Here is a small example from the resource library:
<pre>
> i -src -optimize=share lib/resource/english/LangEng.gf
> p -cat=S ""
> p -cat=S -cfg ""
> p -cat=S -mcfg ""
{Comment: Just some dummy parsing calls to calculate the parsing information}
> p -cat=S -rawtrees=200000 "you will be running"
{Comment: Nr of unfiltered trees: 169296 -- 99,996% av the trees are ill-typed}
UseCl (PosTP TFuture ASimul) (SPredProgVP thou_NP (IPredV AAnter run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP thou_NP (IPredV ASimul run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP ye_NP (IPredV AAnter run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP ye_NP (IPredV ASimul run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP you_NP (IPredV AAnter run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP you_NP (IPredV ASimul run_V))
17730 msec
> p -cat=S -cfg "you will be running"
{Comment: Nr of unfiltered trees: 246 -- 97,5% of the trees are ill-typed}
UseCl (PosTP TFuture ASimul) (SPredProgVP thou_NP (IPredV AAnter run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP thou_NP (IPredV ASimul run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP ye_NP (IPredV AAnter run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP ye_NP (IPredV ASimul run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP you_NP (IPredV AAnter run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP you_NP (IPredV ASimul run_V))
1580 msec
> p -cat=S -mcfg "you will be running"
{Comment: Nr of unfiltered trees: 6 -- all trees are type-corrent}
UseCl (PosTP TFuture ASimul) (SPredProgVP thou_NP (IPredV AAnter run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP thou_NP (IPredV ASimul run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP ye_NP (IPredV AAnter run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP ye_NP (IPredV ASimul run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP you_NP (IPredV AAnter run_V))
UseCl (PosTP TFuture ASimul) (SPredProgVP you_NP (IPredV ASimul run_V))
470 msec
</pre>
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