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Write a fitted vectorizer out without blocking the caller.

public Task SaveAsync(Stream destination, CancellationToken cancellationToken = default)

Parameters — destination is a writable stream, left open. cancellationToken cancels the write.

Returns — Task, completing when the vectorizer has been written.

Exceptions — InvalidOperationException when nothing has been fitted yet, or when the idf weights make a base64 block within two mebibytes of the most the JSON writer holds in one buffer, from 201,129,984 weights. ArgumentException, the JSON writer's own, as 0.7.0 raised it, when a vocabulary term, the token pattern or a stop word is beyond what the writer can write. InvalidDataException when an idf weight is not finite. All are refused before anything is written (#1617, #1618, #1646). NotSupportedException, the stream's own, when it cannot be written to, raised by the write once the artifact is composed, as 0.7.0 raised it. 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. OperationCanceledException when cancelled.

Example — the round trip, asynchronously.

using Lodestar.Text.Vectorization;

static async Task<string> RoundTripAsync()
{
    var tv = new TfidfVectorizer();
    tv.Fit(["the cat eats", "the dog eats"]);

    using var buffer = new MemoryStream();
    await tv.SaveAsync(buffer);
    buffer.Position = 0;

    TfidfVectorizer restored = await TfidfVectorizer.LoadAsync(buffer);
    return restored.GetFeatureNames()[0];
}

string first = RoundTripAsync().GetAwaiter().GetResult();  // => cat

The GetAwaiter().GetResult() is only what lets a synchronous example drive an async one; in async code the call is simply await.

Remarks — as with CountVectorizer.SaveAsync there is no string path overload: opening the file with useAsync: true is the caller's decision, and hiding it here would hide whether the asynchrony reaches the disk.

Applies to — net10.0, netstandard2.0.

See also — TfidfVectorizer.Save, TfidfVectorizer.LoadAsync.