SparseMultiply(_:_:_:_:)
Performs the multiply operation Y = alpha * AX on a sparse matrix of double-precision, floating-point values.
Declaration
func SparseMultiply(_ alpha: Double, _ A: SparseMatrix_Double, _ X: DenseMatrix_Double, _ Y: DenseMatrix_Double)Parameters
- alpha:
The scalar value alpha in Y = alpha * AX.
- A:
The sparse matrix A in Y = AX.
- X:
The dense matrix X in Y = AX.
- Y:
The dense matrix Y in Y = AX.
Discussion
Use this function to multiply a scalar value by a sparse matrix, and then by a dense matrix. The following equation is an example of a scalar-matrix-matrix multiplication where the first matrix is sparse:
[Image]
Call SparseMultiply(_:_:_:_:)to calculate the result.
let rowCount = Int32(4)
let columnCount = Int32(4)
let blockCount = 4
let blockSize = UInt8(1)
let rowIndices: [Int32] = [0, 3, 0, 3]
let columnIndices: [Int32] = [0, 0, 3, 3]
let data = [1.0, 4.0, 13.0, 16.0]
/// The _A_ in _Y = alpha * AX_.
let A = SparseConvertFromCoordinate(rowCount, columnCount,
blockCount, blockSize,
SparseAttributes_t(),
rowIndices, columnIndices,
data)
defer {
SparseCleanup(A)
}
/// The values for _X_ in _Y = alpha * AX_.
var xValues = [10.0, -1.0, -1.0, 10.0,
100.0, -1.0, -1.0, 100.0]
let alpha = 2.0
/// The values for _Y_ in _Y = alpha * AX_.
let yValues = [Double](unsafeUninitializedCapacity: xValues.count) {
resultBuffer, count in
xValues.withUnsafeMutableBufferPointer { denseMatrixPtr in
/// The _X_ in _Y = alpha * AX_.
let X = DenseMatrix_Double(rowCount: 4,
columnCount: 2,
columnStride: 4,
attributes: SparseAttributes_t(),
data: denseMatrixPtr.baseAddress!)
/// The _Y_ in _Y = alpha * AX_.
let Y = DenseMatrix_Double(rowCount: 4,
columnCount: 2,
columnStride: 4,
attributes: SparseAttributes_t(),
data: resultBuffer.baseAddress!)
SparseMultiply(alpha, A, X, Y)
}
count = xValues.count
}
// On return, `yValues` contains:
// `[ 280.0, 0.0, 0.0, 400.0,
// 2800.0, 0.0, 0.0, 4000.0]`