clustergrep

grep for a concept rather than a string, and tell you how far each match is from what you asked for.

grep is mostly used for fixed or moderately varying text that you can determine in advance: a fixed log line string (e.g. "reboot"), a well-formed timestamp, a string which is known to occur around another particular string ("login for niallm failed"). It is a poor fit for the other common search, the one where you know the idea and not the words — for example the concept "escape". Today we use something like grep -E 'escape|flee|jailbreak|breakout', which is inelegant, incomplete, and stale after we invent a new word for something, which we seem to be doing a lot these days. Handing the whole job to a language model trades those problems for different, potentially worse ones: hallucination, skipping lines or an entire file, or answering differently this Tuesday as opposed to last one.

clustergrep splits the difference. A lexical model decides what to look for, once, up front, where you can read it and argue with it. After that, finding it is ordinary deterministic matching with nothing in the loop.

$ clustergrep -t 0.25 escape incidents.log
1:0.00:escape:2024-01-02 The prisoner escaped through the laundry chute.
2:0.25:breakout:2024-01-03 Guards reported a breakout on B wing at 0300.
4:0.20:flee:2024-01-05 Two inmates fled across the yard before dawn.
5:0.25:jailbreak:2024-01-06 A jailbreak attempt was foiled by the perimeter fence.
6:0.25:fly the coop:2024-01-07 He flew the coop while the van was being loaded.
8:0.15:elude:2024-01-09 The suspect eluded officers for six hours.
9:0.15:escapism:2024-01-10 Staff described a general air of escapism among the population.
10:0.20:getaway:2024-01-11 Getaway vehicle recovered near the motorway.
12:0.15:break loose:2024-01-13 The detainee broke loose during transfer.

Of course, this matching surrenders the previous boolean does/doesn't match approach, in favour of a notion of the conceptual distance between the term you searched for and what was found. This means that we report lines that matched, and also the extent to which they matched. In the above, 0.25:jailbreak says this line matched because "jailbreak" is 0.25 away from "escape". You can tweak -t, the flag that sets the conceptual/lexical distance until you're satisfied with the results.

Note "fled" and "broke loose": clustergrep matches irregular inflections, so the cluster does not have to enumerate them.

At the moment clustergrep does not handle non-English, but this is very definitely an ambition. (Technically, the thesaurus is multi-language, but the inflection rules are not.)

Install

One of:

uv tool install clustergrep
pip install clustergrep
pipx install clustergrep

uv tool gives it an isolated environment, so nltk and its dependencies never collide with anything else, and puts clustergrep on your PATH. If the shell cannot find it afterwards, uv tool update-shell. To try it without installing anything, uvx clustergrep -t 0.25 escape incidents.log.

pip install clustergrep works too, and pipx install clustergrep is the same idea as uv tool if that is what you already have.

For the vectors backend, ask for the extra at install time — these environments are isolated, so numpy isn't easily added afterwards.

uv tool install 'clustergrep[vectors]'

The first search will offer to fetch the WordNet corpus, or you can get it over with at the very start:

clustergrep --install-data

You will only be asked to install the data in an interactive terminal; when that's not available (e.g. pipeline, cron job, CI), you get an error telling you to run --install-data.

The corpus is not bundled. As above, WordNet is about 10MB and is licensed separately by Princeton, so clustergrep downloads it on request into a per-user directory rather than shipping a copy. If you already have it — from a previous nltk install, a system package, or NLTK_DATA — that copy is found first and nothing is downloaded.

XDG_DATA_HOME and XDG_CACHE_HOME are honoured wherever they are set, and CLUSTERGREP_DATA / CLUSTERGREP_CACHE override everything — necessary for containers, CI, and read-only home directories.

$ clustergrep --paths
data     /home/you/.local/share/clustergrep
cache    /home/you/.cache/clustergrep
wordnet  /home/you/.local/share/clustergrep/corpora/wordnet.zip

The corpus is fetched once per machine, not once per install: it lives in the data directory rather than the environment, so uvx runs reuse it and switching from uvx to uv tool install will not download it again.

Uninstalling is uv tool uninstall clustergrep (or pip uninstall) and deleting those two directories. Nothing else is written. The cache holds only files clustergrep can rebuild, so deleting it alone is always safe.

From source

git clone https://github.com/niallrmurphy/clustergrep
cd clustergrep
uv pip install -e '.[dev]'
uv run pytest -q

Distance

Distance runs from 0.0 to 1.0.

--threshold 0 admits only the literal word, so clustergrep becomes plain grep. That is exact, not approximate:

$ clustergrep -t 0 --no-inflect -s --no-distance Guards incidents.log
$ grep -n -w -F Guards incidents.log            # identical output

Notable distinction from grep: cluster matching is always word-oriented, like grep -w, because concepts are words, and root/syllabic tokenisation would result in undue implementation complexity right now.

Where the numbers come from

The default backend walks WordNet as a weighted graph with costed edges, and a penalty per "sense". Every distance is therefore a summed path, which --explain will show:

$ clustergrep --explain -t 0.2 escape
'escape' via wordnet, threshold 0.2: 15 term(s)
  0.00  escape
  0.15  break loose  escape.v.01
  0.15  dodging      evasion.n.03
  0.15  elude        elude.v.02
  0.15  escapism     escape.n.02
  0.15  evasion      evasion.n.03
  0.15  flight       escape.n.01
  0.15  get away     escape.v.01
  0.15  get by       get_off.v.05
  0.15  get off      get_off.v.05
  0.15  get out      get_off.v.05
  0.15  miss         miss.v.09
  0.20  escapee      escape.v.01 -derivation-> escapee
  0.20  flee         escape.n.01 -derivation-> flee
  0.20  getaway      escape.v.01 -derivation-> getaway

Narrowing costs less than broadening, because a narrower term keeps you inside the concept while a broader one leaves it. Each successive dictionary sense of the word adds 0.05, so the dominant reading dominates the cluster. There is little that is truly objective about this scoring, but is pragmatically enough to work with right now, and we are open to other suggestions.

Backends

--backend wordnet      (default)  offline, explainable, English
--backend vectors      --model glove.6B.100d.txt
--backend thesaurus    --thesaurus terms.tsv

wordnet just knows lexicographic relations: relatively precise, but only lexically bound, so "escape" and "jail" have no plausible path.

vectors is the opposite. Cosine distance over any GloVe or word2vec text export "knows" that escape → jail immediately but isn't comparably enumerable as a path from an accessible graph search.

thesaurus is a patch file you can use to add your own terms (but replaces WordNet rather than augments it, so you need to seed from the original):

# concept   term          distance   note
escape      jailbreak     0.25
escape      exfil         0.30       our term

clustergrep --explain -t 0.3 escape --tsv > escape.tsv
clustergrep -b thesaurus --thesaurus escape.tsv escape incidents.log

From then on the search is fully reproducible and a new term is a one-line diff.

Options

Familiar from grep: -i -v -c -l -L -o -n -r -m -H --include --exclude --color. Exit codes match too — 0 matched, 1 nothing matched, 2 error.

Particular to this tool:

--stats is for tuning:

$ clustergrep -t 0.4 escape incidents.log --stats -c
10 match(es) from 10 of 62 cluster term(s)
  0.00  escape                   1
  0.25  breakout                 1
  0.20  flee                     1
  0.25  jailbreak                1
  0.25  fly the coop             1
  0.30  leakage                  1
  0.15  elude                    1
  0.15  escapism                 1
  0.20  getaway                  1
  0.15  break loose              1

Large files

Two things go wrong when the corpus is measured in gigabytes and a single line is pages of text: printing matches is useless, and 6MB/s is too slow.

--summary answers the first. It prints no lines at all — only which cluster terms fired and how often, ordered by distance, so you can read the shape of a search that would otherwise scroll for hours:

$ clustergrep -t 0.25 escape big.jsonl --summary
1370 line(s) matched, 1370 match(es), 5 of 40 cluster term(s) fired
  0.00  escape        289
  0.15  elude         279
  0.20  flee          273
  0.25  breakout      277
  0.25  fly the coop  252

Ordering by distance rather than by count is deliberate: it reads as how far did I reach, and what did that buy me -- -t being how far, and the output being what you gained. --summary --json gives those results as one JSON object. When you want the matches themselves rather than a tally, --excerpt prints a window of about 100 characters around each one instead of the whole line:

$ clustergrep -t 0.25 escape big.jsonl --excerpt
1:0.00:escape:…during unusual was wing east the the detainee escaped through a service corridor unusual overnight…
41:0.20:flee:…the sensor although the the two inmates fled across the exercise yard nothing nothing the…
81:0.15:elude:…the and wing the fence duty the suspect eluded officers for several hours shift duty the…

Windows overlapping in the same line are merged, so a paragraph mentioning the concept five times gives one readable excerpt rather than five near-identical ones, and each excerpt is labelled with the distance of the match it actually contains. --excerpt N sets the width; -o is the degenerate case of it, printing the match and nothing else. Under --json the window arrives as an excerpt field in place of text.

--patterns answers the second. It prints every string the matcher would recognise — inflections included — which is exactly what a fast tool needs to throw away the lines that cannot match:

clustergrep -t 0.25 escape --patterns > patterns.txt

rg -Fw -f patterns.txt big.jsonl | clustergrep -t 0.25 escape --summary

ripgrep discards the 98% of lines with nothing in them, and clustergrep does the distance work on what survives. On a 300MB JSONL that is 54 seconds down to 1.5, with byte-identical output.

Use ripgrep, or GNU grep, and not the grep that came with macOS. BSD grep degrades catastrophically on a -f file of a few hundred patterns — measured on the same 300MB JSONL, all three producing identical output:

That is not a typo: on macOS the obvious prefilter is roughly eight times slower than doing no prefiltering at all. brew install ripgrep, or brew install grep for GNU grep as ggrep. On Linux the distribution grep is GNU grep and is fine.

You cannot use --explain output as the pattern file: it holds flee where the text holds fled, so lines are dropped silently. That is what --patterns is for.

Terms that drown the search

At scale the polysemy problem stops being theoretical. Searching a 6GB corpus for escape returned 395,587 matches, of which run, break and miss were 91%. Different terms may be conceptually synonymous in a context, but be textually irrelevant elsewhere; escape can be used directly, or implied by run or break, but run can of course occur in non-escape contexts. Lowering -t doesn't help in all circumstances. However, we can systematically look at the distribution of the usage, and remove the lower fidelity occurrences.

--tune effectively does this:

clustergrep -t 0.25 escape big.jsonl --summary --tune

clustergrep: --tune dropped 3 term(s), cutting at a 11x jump in how often they fire versus the query:
  run                        976    8.9x
  break                      515    4.7x
  miss                       340    3.1x
  re-run without --tune to keep them
319 line(s) matched, 319 match(es), 4 of 37 cluster term(s) fired
  0.00  escape     206
  0.15  flight     59
  0.20  flee       44
  0.25  jailbreak  10

It samples the corpus, counts how often each cluster term fires relative to the query word itself, and cuts at the largest jump in that ratio. The reasoning is that a term appearing ten times more often than the word you actually searched for is not being used in your sense of it.

The cut is made at the jump rather than at a fixed threshold because corpora vary, and any constant is unlikely to be relevant across both.

The flag does nothing rather than guess when the query is too rare in the sample to measure against, or when there is no clear separation, and it never drops a term firing less often than the query. It always says what it did, on stderr. It does not silently discard terms.

Of course, this is a heuristic, and as such can fail or have edge cases: search for automobile in a corpus that says car, and car looks exactly like run does. That is what the stderr report is for — if it drops something you wanted, drop --tune and pin a thesaurus instead.

If the interesting text is one field of a JSONL record, cut it out first and scan less:

jq -r '.text' big.jsonl | rg -Fw -f patterns.txt | clustergrep -t 0.25 escape --summary

One caveat on all of these: -F matches literally, so a hyphenated multi-word term (e.g. fly-the-coop) will of course be treated literally. clustergrep itself accepts spaces, hyphens and underscores interchangeably, so the second pass is more permissive than the first.

Known limits

Polysemy. A cluster covers every sense of the word. At -t 0.4, "escape" reaches leakage and outflow via the concept of fluid-discharge, so a line about reactor coolant will match.

--tune is statistical, not semantic. It can only see how often a term fires, so a genuine synonym that happens to be commoner than your query looks identical to a polysemous intruder. It reports every term it drops for exactly this reason.

Distances are not probabilities and are not comparable between backends. They only order matches within one search.

English only, and only as current as WordNet 3.0.

Irregular inflections (fled, broke, flew) come from WordNet's exception lists and apply to every backend, including a thesaurus you pinned by hand — which spellings of a word exist is a fact about English, not about where the cluster came from. They are lost only if the corpus is not installed; clustergrep --paths will tell you. --no-inflect switches off regular and irregular forms together.

Speed. Between about 4 and 6MB/s, against 0.1s for grep -E on the same file. This comes from Python's regex engine working over an alternation of a few hundred patterns, and is what produces the extra columns. Expect the lower end on a first read of a large file and the upper end once it is in the page cache; line length and match density barely matter, and non-ASCII text costs a few percent. See Large files for a way around it.

Licence

clustergrep is MIT licensed. The WordNet corpus it downloads is not part of this distribution and is covered by Princeton's WordNet licence. Any vector model you point --model at carries whatever licence its publisher gave it.