wehub-resource-sync
90 lines
2.9 KiB
C#
90 lines
2.9 KiB
C#
// Copyright (c) Microsoft. All rights reserved.
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using Microsoft.SemanticKernel;
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using Microsoft.SemanticKernel.ChatCompletion;
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namespace ChatCompletion;
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/// <summary>
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/// Implementation of <see cref="IChatHistoryReducer"/> which trim to the specified max token count.
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/// </summary>
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/// <remarks>
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/// This reducer requires that the ChatMessageContent.MetaData contains a TokenCount property.
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/// </remarks>
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public sealed class ChatHistoryMaxTokensReducer : IChatHistoryReducer
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{
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private readonly int _maxTokenCount;
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/// <summary>
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/// Creates a new instance of <see cref="ChatHistoryMaxTokensReducer"/>.
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/// </summary>
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/// <param name="maxTokenCount">Max token count to send to the model.</param>
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public ChatHistoryMaxTokensReducer(int maxTokenCount)
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{
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if (maxTokenCount <= 0)
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{
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throw new ArgumentException("Maximum token count must be greater than zero.", nameof(maxTokenCount));
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}
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this._maxTokenCount = maxTokenCount;
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}
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/// <inheritdoc/>
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public Task<IEnumerable<ChatMessageContent>?> ReduceAsync(IReadOnlyList<ChatMessageContent> chatHistory, CancellationToken cancellationToken = default)
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{
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var systemMessage = chatHistory.GetSystemMessage();
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var truncationIndex = ComputeTruncationIndex(chatHistory, systemMessage);
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IEnumerable<ChatMessageContent>? truncatedHistory = null;
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if (truncationIndex > 0)
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{
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truncatedHistory = chatHistory.Extract(truncationIndex, systemMessage: systemMessage);
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}
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return Task.FromResult<IEnumerable<ChatMessageContent>?>(truncatedHistory);
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}
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#region private
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/// <summary>
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/// Compute the index truncation where truncation should begin using the current truncation threshold.
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/// </summary>
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/// <param name="chatHistory">Chat history to be truncated.</param>
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/// <param name="systemMessage">The system message</param>
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private int ComputeTruncationIndex(IReadOnlyList<ChatMessageContent> chatHistory, ChatMessageContent? systemMessage)
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{
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var truncationIndex = -1;
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var totalTokenCount = (int)(systemMessage?.Metadata?["TokenCount"] ?? 0);
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for (int i = chatHistory.Count - 1; i >= 0; i--)
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{
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truncationIndex = i;
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var tokenCount = (int)(chatHistory[i].Metadata?["TokenCount"] ?? 0);
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if (tokenCount + totalTokenCount > this._maxTokenCount)
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{
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break;
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}
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totalTokenCount += tokenCount;
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}
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// Skip function related content
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while (truncationIndex < chatHistory.Count)
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{
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if (chatHistory[truncationIndex].Items.Any(i => i is FunctionCallContent or FunctionResultContent))
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{
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truncationIndex++;
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}
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else
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{
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break;
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}
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}
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return truncationIndex;
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}
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#endregion
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}
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