/// <inheritdoc/>
public bool TrySerializeAndSave(string filePath, object serializeableObject)
{
try
{
AtomicFileWriter.Write(
filePath,
(xmlStream) => {
XmlUtils.SerializeToXmlStream(serializeableObject, xmlStream, Encoding.UTF8);
});
return(true);
}
catch (Exception)
{
return(false);
}
}
/// <summary>
/// Construct an SPM model from data; that is, train one.
/// The input is passed as an IEnumerable or a ParallelQuery of lines of raw plain-text.
/// The model is returned as a binary blob (for later use in encoding/decoding).
/// Underneath, this uses the spm_train executable, which needs to store the model as a file. That location is
/// passed in as 'tempSPMModelPath'. These output files are temporary and local to this function, but
/// it is useful to keep them around for diagnostics and debugging; they are not (meant to be) used after this.
/// 'minPieceCount' allows to set a minimum observation count for word pieces. spm_train does not support this,
/// so we emulate/approximate it by running spm_train twice.
/// </summary>
public static SentencePieceModel Train <Enumerable>(Enumerable tokenStrings, string tempSPMModelPath,
SentencePieceTrainConfig spmParams, int minPieceCount, string spmBinDir)
where Enumerable : IEnumerable <string> // using template so we won't loose parallelism (is this needed?)
{
Sanity.Requires(tempSPMModelPath.EndsWith(spmModelExt), $"FactoredSegmenter SentencePiece model path must end in {spmModelExt}");
var modelPrefix = tempSPMModelPath.Substring(0, tempSPMModelPath.Length - spmModelExt.Length);
#if false // helper during debugging of final Training stage when models already exist
LoadSPMModelFiles(modelPrefix, out var spmModelBlob, out var spmVocab);
#else
// write the tokens to a temp file
var tempInputDataPath = modelPrefix + ".data";
Logger.WriteLine($"FactoredSegmenter: Writing to temp file {tempInputDataPath} for SPM training...");
AtomicFileWriter.Save(tempInputDataPath, tmpPath => File.WriteAllLines(tmpPath, tokenStrings, new UTF8Encoding()));
// atomic writing allows the impatient user to know when the writing has completed and spm_train has taken over
// invoke spm_train
SPMTrain(tempInputDataPath, modelPrefix, spmParams, spmBinDir, null);
// fetch the content of the generated .model and .vocab file into in-memory data structures
// After this, the spm_train-generated files are no longer used; and only kept for debugging purposes.
LoadSPMModelFiles(modelPrefix, out var spmModelBlob, out var spmVocab);
// enforce minimum piece-count constraint
if (minPieceCount > 1)
{
// encode the SPM training data and count each token's occurence
Logger.WriteLine($"FactoredSegmenter: Minimum-count constraint ({minPieceCount}), counting SPM tokens...");
var coder = new SentencePieceCoder(new SentencePieceCoderConfig {
SentencePieceModel = new SentencePieceModel(spmModelBlob)
});
var counts = CountEncodedTokens(tempInputDataPath, coder);
File.WriteAllLines(tempSPMModelPath + $".{spmVocab.Length}.counts", // save it for diagnostics only
from kvp in counts orderby - kvp.Value, kvp.Key select $"{kvp.Key}\t{kvp.Value}");
// count number of SPM vocab items that should be kept (above the threshold or single character which we always keep)
var spmVocabSet = new HashSet <string>(spmVocab);
int adjustedVocabSize = counts.Count(kvp => spmVocabSet.Contains(kvp.Key) && (kvp.Key.Length == 1 || kvp.Value >= minPieceCount));
// if there are units below the threshold, reduce the SPM vocab size and retrain
if (adjustedVocabSize < spmVocab.Length)
{
Logger.WriteLine($"FactoredSegmenter: Only {adjustedVocabSize} out of {spmVocab.Length} sentence pieces have {minPieceCount} or more observations." +
$" Retraining SPM model with reduced vocabSize {adjustedVocabSize}");
// invoke spm_train a second time
SPMTrain(tempInputDataPath, modelPrefix, spmParams, spmBinDir, adjustedVocabSize);
LoadSPMModelFiles(modelPrefix, out spmModelBlob, out spmVocab); // reload the new model
}
// count once again for diagnostics only
Logger.WriteLine($"FactoredSegmenter: Re-counting SPM tokens after reduction to {adjustedVocabSize}...");
coder = new SentencePieceCoder(new SentencePieceCoderConfig {
SentencePieceModel = new SentencePieceModel(spmModelBlob)
});
counts = counts = CountEncodedTokens(tempInputDataPath, coder);
File.WriteAllLines(tempSPMModelPath + $".{adjustedVocabSize}.counts", // save for diagnostics only
from kvp in counts orderby - kvp.Value, kvp.Key select $"{kvp.Key}\t{kvp.Value}");
}
// delete the temp file --except if it failed, so user can double-check what's going on
// commented out temporarily to aid debugging
//File.Delete(tempPath);
#endif
return(new SentencePieceModel(spmModelBlob));
}
