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HashingVectorizer.Save

Write the options out, which is all there is to write.

public void Save(Stream destination)
public void Save(string path)

Parameters — destination is a writable stream, left open for the caller to dispose; path is a file to create or overwrite.

Exceptions — ArgumentException, the JSON writer's own, as 0.7.0 raised it, when the token pattern or a stop word is beyond what the writer can write. InvalidDataException when MinDf or MaxDf is not finite, which the constructor does not refuse. Both are refused before a byte is written: once the writer has accepted the stream, or once the file is open (#1618, #1622, #1646). ArgumentException too when the stream cannot be written to, refused before the options' strings are checked (#1641). IndexOutOfRangeException, the writer's own as well, for a string whose escaped form passes its buffer, as 0.7.0 raised it. ArgumentNullException for a null stream or path. IOException from the stream or file system.

Example — a round trip that carries the settings and nothing else.

using Lodestar.Text.Vectorization;

var hv = new HashingVectorizer(new HashingVectorizerOptions { NumFeatures = 16 });

using var buffer = new MemoryStream();
hv.Save(buffer);
buffer.Position = 0;

HashingVectorizer restored = HashingVectorizer.Load(buffer);
int columns = restored.NumFeatures;  // => 16

Remarks — there is no fit to save, so this writes the options alone, and unlike its counterparts it never throws for being unfitted — there is no such state.

Whether it is worth saving at all is a fair question, and the answer is that it keeps the three vectorizers interchangeable: code that persists a fitted model works unchanged when the model is this one. The file is small.

The write is not bounded the way a load is. A stop-word list past a default of ArtifactLoadOptions — a word over 1024 characters, more than a million words — saves, and loads only with that bound raised.

Applies to — net10.0, netstandard2.0.

See also — HashingVectorizer.Load, HashingVectorizer.SaveAsync.