OpenFst - Release 1.5.3

OpenFst is a library for constructing, combining, optimizing, and searching weighted finite-state transducers (FSTs).


This version is known to work under Linux using g++ (≥ 4.7) and MacOS X using XCode (≥ 5). Expected to work wherever adequate POSIX (dlopen, ssize_t, basename), c99 (snprintf, strtoll, <stdint.h>), and C++11 (<ordered_set>, <ordered_map>, <forward_list>) support are available.


Follow the generic GNU build system instructions in ./INSTALL. We recommend configuring with --enable-static=no for faster compiles.

Optional features:

Option Description Default
--enable-bin Enable fst::script and command-line binaries yes
--enable-compact-fsts Enable all CompactFst extensions no
--enable-compress Enable compression extension no
--enable-const-fsts Enable all ConstFst extensions no
--enable-far Enable FAR extensions no
--enable-linear-fsts Enable LinearTagger/ClassifierFst extensions no
--enable-lookahead-fsts Enable LookAheadFst classes no
--enable-mpdt Enable MPDT extensions no
--enable-ngram-fsts Enable NGramFst extensions no
--enable-pdt Enable PDT extensions no
--enable-python Enable Python extensions no

Configuring with --enable-bin=no gives very fast compiles, but excludes the command line utilities.

Configuring with --enable-python will attempt to install the Python module to whichever site-packages (or dist-packages, on Debian or Ubuntu) is found during configuration.

Compiling with -Wall -Wno-sign-compare under g++ should give no warnings from this library.


Assuming you've installed under the default /usr/local, the FST binaries are found on /usr/local/bin.

To use in your own program, include <fst/fstlib.h> and compile with -I /usr/local/include. The compiler must support C++11 (for g++ add the flag -std=c++11). Link against /usr/local/lib/ and -ldl. Set your LD_LIBRARY_PATH (or equivalent) to contain /usr/local/lib.

The linking is, by default, dynamic so that the Fst and Arc type DSO extensions can be used correctly if desired. Any extensions will normally be found under /usr/local/lib/fst.


See for general documentation. See ./NEWS for updates since the last release.
Topic revision: r25 - 2016-05-24 - KyleGorman
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