adding sbs2fst

tools/README.md

@@ -25,3 +25,40 @@ A simple bash script that is meant for benchmarking the resource (RAM and runtim
 
 Example usage:
 `bash gather_runtime_metrics.sh output_for_this_release.csv`
+
+## sbs2fst.py
+A python interface to simplify the conversion of a side-by-side file, generated from fstalign's `--output-sbs` flag, into [files that can be used to produce an FST using OpenFST](https://www.openfst.org/twiki/bin/view/FST/FstQuickTour).
+
+Example usage:
+
+`python sbs2fst.py sbs_file.txt fst_file_name`
+
+The output will be two files: `fst_file_name.fst` which will describe the FST in the AT&T FSM format used by OpenFST, and `fst_file_name.txt` which contains the complete list of symbols in the FST.
+
+The additional flags can be passed into the python script to add metadata that fstalign uses for tracking performance. These are useful to understand when fstalign picks tokens that are: only in the side-by-side's `ref_token` column (labeled by the `--left` flag), only in the side-by-side's `hyp_token` column (labeled by the `--right` flag), or in both columns because the `ref_token` and `hyp_token` agree (labeled by the `--gold` flag). 
+
+Example usage:
+
+`python sbs2fst.py --tag --left VERBATIM --right NONVERBATIM --gold AGREEMENT sbs_file.txt fst_file_name`
+
+The output will produce an FST with tags indicating tokens that were only in the `ref_token` with `VERBATIM`, tokens that were only in the `hyp_token` with `NONVERBATIM`, and tokens that were in both columns with `AGREEMENT`. 
+
+### Compiling the FST
+Once you have used `sbs2fst.py` to produce the `.txt` and `.fst` files, you *must* then compile the FST before passing it into fstalign. An example command can be found below:
+
+`fstcompile --isymbols=${SYMBOLS} --osymbols=${SYMBOLS} ${TXT_FST} ${COMPILED_FST}`
+
+where `SYMBOLS` is the `.txt` file produced by `sbs2fst.py`, `TXT_FST` is the `.fst` file, and `COMPILED_FST` is a new `.fst` file that produces the binary FST usable by fstalign.
+
+Example usage:
+```bash
+python sbs2fst.py --tag --left VERBATIM --right NONVERBATIM --gold AGREEMENT sbs_file.txt fst_file_name
+fstcompile --isymbols=fst_file_name.txt --osymbols=fst_file_name.txt fst_file_name.fst fst_file_name.compiled.fst
+```
+You can now use `fst_file_name.compiled.fst` in fstalign with the corresponding symbols file as follows:
+```bash
+fstalign --ref fst_file_name.complied.fst --symbols fst_file_name.txt ...
+```
+
+Note that when you `sbs2fst.py` to produce a "tagged" FST with the `--tag` flag, fstalign will aggregate WER metrics for each of the specified tags (`--left`, `--right`, and `--gold`) in the JSON log file specified by fstalign's `--json-log` flag.
+

tools/sbs2fst.py

@@ -0,0 +1,326 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2023
+# Author: Miguel Ángel del Río Fernández <miguel.delrio@rev.com>
+# All Rights Reserved
+
+from argparse import ArgumentParser
+from collections import OrderedDict
+from dataclasses import dataclass, field
+from itertools import takewhile
+from pathlib import Path
+from typing import Dict, Generator, List, Optional, Tuple
+
+
+@dataclass
+class SbsEntry:
+    """ Represent a single SBS line."""
+    ref_word: str
+    hyp_word: str
+    error: bool
+    entity_class: str
+    wer_tags: List[str] = field(default_factory=list)
+    extra_columns: List[str] = field(default_factory=list)
+
+    @classmethod
+    def from_line(cls, line: str) -> 'SbsEntry':
+        parts = line.strip(' \n').split('\t')
+        if len(parts) == 4:
+            # old format
+            entry = SbsEntry(parts[0].strip(), parts[1].strip(),
+                    parts[2] == 'ERR', parts[3])
+        elif len(parts) == 5:
+            # New format, wer_tags
+            entry = SbsEntry(parts[0].strip(), parts[1].strip(),
+                    parts[2] == 'ERR', parts[3],
+                    [tag for tag in parts[4].split('|') if tag])
+        elif len(parts) > 5:
+            entry = SbsEntry(parts[0].strip(), parts[1].strip(),
+                    parts[2] == 'ERR', parts[3],
+                    [tag for tag in parts[4].split('|') if tag],
+                    extra_columns=parts[5:])
+        else:
+            raise RuntimeError(f"Could not parse the line as SBS:\n{line}")
+        return entry
+
+    def __str__(self):
+        if self.error:
+            err_str = "ERR"
+        else:
+            err_str = ""
+        wer_tags_str = "|".join(self.wer_tags)
+        if wer_tags_str:
+            wer_tags_str += "|"
+        return '\t'.join([self.ref_word, self.hyp_word, err_str,
+            self.entity_class, wer_tags_str]+self.extra_columns)
+
+
+def load_from_file(fp: Path) -> Generator[SbsEntry, None, None]:
+    with open(fp) as f:
+        f.readline()
+        lines = takewhile(lambda x: not x.startswith("--------"), f.readlines())
+        for line in lines:
+            yield SbsEntry.from_line(line)
+
+
+class FSTState:
+    def __init__(self):
+        self.state: int = 0
+        self.vocabulary: OrderedDict = OrderedDict({"<eps>": 0})
+        self.unique_id: int = 0
+
+    def update_vocabulary(self, word):
+        """If `word` isn't in `self.vocabulary` add it
+        with it's own unique id."""
+        if word not in self.vocabulary:
+            self.vocabulary[word] = len(self.vocabulary)
+
+    def get_uid(self):
+        """Return the `self.unique_id` and increment it
+        by one."""
+        current_uid = self.unique_id
+        self.unique_id += 1
+        return current_uid
+
+
+def init_args():
+    parser = ArgumentParser(description="SBS to FST")
+    parser.add_argument("sbs_file", type=Path, help="The input SBS file")
+    parser.add_argument("fst_file", type=Path, help="The output FST file")
+    parser.add_argument(
+        "--left",
+        type=str,
+        default="LEFT",
+        help="Label for the left column. This label will be given to "
+        "words that occur on the left (reference) side of the SBS "
+        "during an ERR.",
+    )
+    parser.add_argument(
+        "--right",
+        type=str,
+        default="RIGHT",
+        help="Label for the right column. This label will be given to "
+        "words that occur on the right (hypothesis) side of the SBS "
+        "during an ERR.",
+    )
+    parser.add_argument(
+        "--gold",
+        type=str,
+        default="GOLD",
+        help="Label for the gold column. This is for words that both "
+        "transcripts agree upon in the SBS.",
+    )
+    parser.add_argument(
+        "--tag",
+        action="store_true",
+        help="If set, the script will add extra tagging information",
+    )
+    return parser.parse_args()
+
+
+def prepare_IO(
+    input: Path,
+    output: Path,
+):
+    """Determines if the input is a directory or file and prepares output accordingly"""
+    input_files = []
+    output_files = []
+    if input.is_dir():
+        output.mkdir(parents=True, exist_ok=True)
+        for file in input.glob("**/*.txt"):
+            input_files.append(file)
+            output_files.append(output / file.stem)
+    else:
+        input_files = [input]
+        output_files = [output]
+    return input_files, output_files
+
+
+def _to_fst_line(state1, state2, arc, weight: float=0):
+    return f"{state1} {state2} {arc} {arc} {weight}"
+
+
+def flush_span(
+    span: List[str], state: int, *, tag: Optional[str] = None, branch_factor: int = 0
+) -> Tuple[List[str], int]:
+    """Flush the span by generating the relevant fst lines. If `tag`
+    is set add surrounding fst lines to correspond to the tag.
+    `branch_factor` can also be set to increase the initial transition
+    from the tag state to the first span state (SHOULD ONLY BE USED IN
+    COMBINATION WITH `tag`).
+    The primary use of the `branch_factor` is for the right side during
+    a disagreement -- you want the first right-side arc to go from the same
+    start as the left-side to a new state that isn't used by the left side
+    at all. So by specifying the `branch_factor` you can "skip" states.
+    In the context of a disagreement, the left-side will have 0 `branch_factor`
+    while the right-side must have a `branch_factor` the size of left-side
+    length.
+    """
+    if len(span) == 0:
+        return [], state
+
+    span_state = state + branch_factor + 1
+    if tag:
+        fst_lines = [_to_fst_line(state, span_state, tag)]
+    else:
+        fst_lines = [_to_fst_line(state, span_state, span[0])]
+        span = span[1:]
+
+    for token in span:
+        fst_lines.append(_to_fst_line(span_state, span_state + 1, token))
+        span_state += 1
+
+    if tag:
+        fst_lines.append(_to_fst_line(span_state, span_state + 1, tag))
+        span_state += 1
+    return fst_lines, span_state
+
+
+def agreement_flush(
+    gold_span: List[str], fst_state: FSTState, *, tag: bool = False, gold: Optional[str] = None
+) -> List[str]:
+    """Flush "gold" spans when both sides of the sbs agree and update the FSTState.
+    If `tag` is True, adds a unique tag around the span using `gold` to label.
+    """
+    gold_tag = None
+    if tag:
+        gold_tag = f"___MULTIREF:{fst_state.get_uid()}_{gold}___"
+        fst_state.update_vocabulary(gold_tag)
+
+    gold_fst_lines, new_state = flush_span(gold_span, fst_state.state, tag=gold_tag)
+    fst_state.state = new_state
+
+    return gold_fst_lines
+
+
+def disagreement_flush(
+    left_span: List[str],
+    right_span: List[str],
+    fst_state: FSTState,
+    *,
+    tag: bool = False,
+    left: Optional[str] = None,
+    right: Optional[str] = None,
+) -> List[str]:
+    """Flush the left and right spans when transcripts disagree and update the FSTState.
+    If `tag` is True, adds a unique tag around the left span using `left` to label and
+    around the right span using `right` to label.
+    """
+    fst_lines = []
+
+    left_tag = None
+    if tag:
+        left_tag = f"___MULTIREF:{fst_state.get_uid()}_{left}___"
+        fst_state.update_vocabulary(left_tag)
+
+    left_fst_lines, left_end_state = flush_span(left_span, fst_state.state, tag=left_tag)
+    fst_lines.extend(left_fst_lines)
+
+    right_tag = None
+    if tag:
+        right_tag = f"___MULTIREF:{fst_state.get_uid()}_{right}___"
+        fst_state.update_vocabulary(right_tag)
+
+    right_fst_lines, right_end_state = flush_span(
+        right_span, fst_state.state, tag=right_tag, branch_factor=len(left_fst_lines)
+    )
+    fst_lines.extend(right_fst_lines)
+
+    max_end_state = max(left_end_state, right_end_state)
+    # We have to return both paths back to same state to progress
+    fst_lines.append(_to_fst_line(left_end_state, max_end_state + 1, "<eps>"))
+    fst_lines.append(_to_fst_line(right_end_state, max_end_state + 1, "<eps>"))
+
+    fst_state.state = max_end_state + 1
+
+    return fst_lines
+
+
+def sbs2fst(
+    sbs_file: Path,
+    *,
+    tag: bool = False,
+    gold: Optional[str] = None,
+    left: Optional[str] = None,
+    right: Optional[str] = None,
+) -> Tuple[List[str], Dict[str, int]]:
+    """Given an `sbs_file` create the equivalent fst object.
+    Optionally you can include tags by setting `tag` to true. These will be distinguished by the
+    tag labels provided in `gold` (agreements), `left` (words on the reference side of the sbs not in hypothesis),
+    and `right` (words on the hypothesis side of the sbs not in reference).
+    """
+    sbs = load_from_file(sbs_file)
+
+    fst_state = FSTState()
+    fst_lines = []
+
+    left_span = []
+    right_span = []
+    gold_span = []
+    for row_idx, row in enumerate(sbs):
+        ref_word = "<eps>" if row.ref_word == "<ins>" else row.ref_word
+        hyp_word = "<eps>" if row.hyp_word == "<del>" else row.hyp_word
+
+        fst_state.update_vocabulary(ref_word)
+        fst_state.update_vocabulary(hyp_word)
+
+        if row.ref_word == row.hyp_word:
+            # First flush the left & right spans to empty any disagreements
+            if len(left_span) > 0 or len(right_span) > 0:
+                disagreement_fst_lines = disagreement_flush(
+                    left_span, right_span, fst_state, tag=tag, left=left, right=right
+                )
+                fst_lines.extend(disagreement_fst_lines)
+                left_span = []
+                right_span = []
+            gold_span.append(row.ref_word)
+        else:
+            # First flush the gold span to empty any agreements
+            if len(gold_span) > 0:
+                gold_fst_lines = agreement_flush(gold_span, fst_state, tag=tag, gold=gold)
+                fst_lines.extend(gold_fst_lines)
+                gold_span = []
+
+            if ref_word != "<eps>":
+                left_span.append(ref_word)
+            if hyp_word != "<eps>":
+                right_span.append(hyp_word)
+
+    # Flush the spans that have infomration. It'll only be a gold or a disagreement. Not both
+    if len(gold_span) > 0:
+        gold_fst_lines = agreement_flush(gold_span, fst_state, tag=tag, gold=gold)
+        fst_lines.extend(gold_fst_lines)
+    elif len(left_span) > 0 or len(right_span) > 0:
+        disagreement_fst_lines = disagreement_flush(
+            left_span, right_span, fst_state, tag=tag, left=left, right=right
+        )
+        fst_lines.extend(disagreement_fst_lines)
+
+    fst_lines.append(f"{fst_state.state}")
+
+    return fst_lines, fst_state.vocabulary
+
+
+def main(
+    sbs_file: Path,
+    fst_file: Path,
+    tag: bool = False,
+    gold: Optional[str] = None,
+    left: Optional[str] = None,
+    right: Optional[str] = None,
+):
+    for inpath, outpath in zip(*prepare_IO(sbs_file, fst_file)):
+        fst_lines, vocabulary = sbs2fst(inpath, tag=tag, gold=gold, left=left, right=right)
+
+        with open(f"{outpath}.fst", "w") as fstfile:
+            fstfile.write("\n".join(fst_lines))
+
+        with open(f"{outpath}.txt", "w") as fstfile:
+            for key, value in vocabulary.items():
+                fstfile.write(f"{key} {value}\n")
+
+
+if __name__ == "__main__":
+    args = init_args()
+    main(**vars(args))