fstisomorphic(1)

👑 fstisomorphic, but make it make sense

okay bestie, welcome to section 1 of the manual — User Commands — this is the page for fstisomorphic, and yes we are going to be normal about it (we are not going to be normal about it).

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✨ NAME ✨

fstisomorphic — figure out whether two FSTs are equal 🦋

Like, the same. Isomorphic. Twinning. Matching outfits. periodt.

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🌸 SYNOPSIS 🌸

fstisomorphic [OPTIONS] in1.fst in2.fst

Two files in, one tiny little vibe check out. 💅

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💖 DESCRIPTION 💖

So here's the tea: fstisomorphic determines whether two FSTs are isomorphic. 👑

The exit status is zero for isomorphic FSTs, and nonzero otherwise. That's it. That's the whole thing. It either slays or it doesn't. 🎀

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🌈 OPTIONS 🌈

quick lil heads up before we dive in, bestie: boolean options accept either true or false as a value, or the implicit value true if neither value is specified. So if you just slap the flag on with no value, congrats, you said true. no cap. ✨

• --delta=VALUE — set the comparison/quantization delta. Default: 0.000976562. tiny number, big responsibilities 🫶
• --fst_align[=BOOLEAN] — write FST data aligned where appropriate. Default: false.
• --fst_compat_symbols[=BOOLEAN] — require symbol tables to match when appropriate. Default: true. yes ma'am, we're checking IDs 👑
• --fst_default_cache_gc[=BOOLEAN] — enable garbage collection of cache. Default: true. the cache is getting cleaned, it's giving self-care 🧚
• --fst_default_cache_gc_limit=N — set the cache byte size that triggers garbage collection. Default: 1048576.
• --fst_error_fatal[=BOOLEAN] — if true, FST errors are fatal. Otherwise, returned objects are flagged as bad. For example, FSTs are returned with the kError property set to true, and FST weights set so that Member() returns false. Default: true. 🚨
• --fst_field_separator=STRING — set the characters used as a separator between printed fields. Default: " " (yep, literally five spaces, she's subtle).
• --fst_read_mode=STRING — set the default file reading mode for mappable files, either "read" or "map". Default: "read".
• --fst_verify_properties[=BOOLEAN] — verify fst properties queried by TestProperties. Default: false.
• --fst_weight_parentheses=STRING — set the characters enclosing the first weight of a printed composite weight (e.g., pair weight, tuple weight, and derived classes) to ensure proper I/O of nested composite weights. Must have size 0 (none) or 2 (open and close parenthesis). Default: no parentheses.
• --fst_weight_separator=CHARACTER — set the character separator between printed composite weights. Default: comma.
• --help[=BOOLEAN] — show usage information. Default: false. bestie if you're lost, start here 🙈
• --helpshort[=BOOLEAN] — show brief usage information. Default: false. the TL;DR version, obsessed 😭
• --save_relabel_ipairs=FILENAME — save input relabel pairs to file. Default: do not save.
• --save_relabel_opairs=FILENAME — save output relabel pairs to file. Default: do not save.
• --tmpdir=PATHNAME — set the temporary directory to use. Default: /tmp.
• --v[=N] — set the verbosity level. Default: 0. crank it up if you want her to talk more 💀

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🦋 SEE ALSO 🦋

the whole friend group showed up, and we are not leaving anybody out (main character energy for all of them):

fstarcsort(1), fstclosure(1), fstcompile(1), fstcompose(1), fstcompress(1), fstconcat(1), fstconnect(1), fstconvert(1), fstdeterminize(1), fstdifference(1), fstdisambiguate(1), fstdraw(1), fstencode(1), fstepsnormalize(1), fstequal(1), fstequivalent(1), fstinfo(1), fstintersect(1), fstinvert(1), fstlinear(1), fstloglinearapply(1), fstmap(1), fstminimize(1), fstprint(1), fstproject(1), fstprune(1), fstpush(1), fstrandgen(1), fstrelabel(1), fstreplace(1), fstreverse(1), fstreweight(1), fstrmepsilon(1), fstshortestdistance(1), fstshortestpath(1), fstsymbols(1), fstsynchronize(1), fsttopsort(1), fstunion(1)

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if the exit status is zero, they're isomorphic and you should celebrate. if it's nonzero, they're not, and that's also fine, we don't yuck anybody's graph. 💜

this page came from OpenFst 1.8.5, dated Mar 2026 — ty for coming to my ted talk, go check if ur FSTs match, ily, bye 💖✨