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Updates the kvcache func in TextDecoder to work with Swift6 #289

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Updates the kvcache func in TextDecoder to work with Swift6 #289

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82 changes: 43 additions & 39 deletions Sources/WhisperKit/Core/TextDecoder.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -308,45 +308,49 @@ public extension TextDecoding {
return kvCache
}

static func updateKVCache(keyTensor: MLMultiArray, keySlice: MLMultiArray,
valueTensor: MLMultiArray, valueSlice: MLMultiArray,
insertAtIndex index: Int)
{
let tensorShape = keyTensor.shape.map { $0.intValue }
let sliceShape = keySlice.shape.map { $0.intValue }
let sliceStrides = keySlice.strides.map { $0.intValue } // same for val
let bytesPerSample = MemoryLayout<FloatType>.size

keyTensor.withUnsafeMutableBytes { keyTensorPointer, keyTargetStrides in
keySlice.withUnsafeBytes { keySlicePointer in
valueTensor.withUnsafeMutableBytes { valueTensorPointer, valueTargetStrides in
valueSlice.withUnsafeBytes { valueSlicePointer in
// Assuming batch size is always 1
DispatchQueue.concurrentPerform(iterations: tensorShape[1]) { j in
// Slice size is 3 for prefill and 1 for decode loops
for k in 0..<sliceShape[3] {
// Equivalent to:
// `tensor[0, j, 0, k + index] = slice[0, j, 0, k + index]`
let keyDestIndex = j * keyTargetStrides[1] + (index + k) * keyTargetStrides[3]
let keyDest = keyTensorPointer.baseAddress! + keyDestIndex * bytesPerSample

let keySliceIndex = j * sliceStrides[1] + k * sliceStrides[3]
let keySlice = keySlicePointer.baseAddress! + keySliceIndex * bytesPerSample
memcpy(keyDest, keySlice, bytesPerSample)

let valDestIndex = j * valueTargetStrides[1] + (index + k) * valueTargetStrides[3]
let valDest = valueTensorPointer.baseAddress! + valDestIndex * bytesPerSample

let valSliceIndex = j * sliceStrides[1] + k * sliceStrides[3]
let valSlice = valueSlicePointer.baseAddress! + valSliceIndex * bytesPerSample
memcpy(valDest, valSlice, bytesPerSample)
}
}
}
}
}
}
}
static func updateKVCache(keyTensor: MLMultiArray, keySlice: MLMultiArray,
valueTensor: MLMultiArray, valueSlice: MLMultiArray,
insertAtIndex index: Int)
{
let tensorShape = keyTensor.shape.map { $0.intValue }
let sliceShape = keySlice.shape.map { $0.intValue }

// Create flat arrays for safe concurrent access
var keyData = [FloatType](repeating: 0, count: keyTensor.count)
var valueData = [FloatType](repeating: 0, count: valueTensor.count)

// Get current tensor data
memcpy(&keyData, keyTensor.dataPointer, keyTensor.count * MemoryLayout<FloatType>.size)
memcpy(&valueData, valueTensor.dataPointer, valueTensor.count * MemoryLayout<FloatType>.size)

// Calculate dimensions for index mapping
let seqLength = tensorShape[3]
let hiddenDim = tensorShape[1]

// Concurrent processing across hidden dimension
DispatchQueue.concurrentPerform(iterations: hiddenDim) { j in
for k in 0..<sliceShape[3] {
// Calculate linear indices
let targetSeqPos = index + k
guard targetSeqPos < seqLength else { continue }

// Map 4D indices [0, j, 0, index+k] to linear index
let flatKeyIndex = j * seqLength + targetSeqPos
let flatSliceIndex = j * sliceShape[3] + k

// Copy from slice to tensor
let sliceKeyPtr = keySlice.dataPointer.assumingMemoryBound(to: FloatType.self)
let sliceValuePtr = valueSlice.dataPointer.assumingMemoryBound(to: FloatType.self)

keyData[flatKeyIndex] = sliceKeyPtr[flatSliceIndex]
valueData[flatKeyIndex] = sliceValuePtr[flatSliceIndex]
}
}

// Copy data back to tensors
memcpy(keyTensor.dataPointer, &keyData, keyTensor.count * MemoryLayout<FloatType>.size)
memcpy(valueTensor.dataPointer, &valueData, valueTensor.count * MemoryLayout<FloatType>.size)
}

static func updateAlignmentWeights(
alignmentTensor: MLMultiArray,
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