---
title: "SparseMultiplyAdd(_:_:_:_:)"
framework: accelerate
role: symbol
role_heading: Function
path: "accelerate/sparsemultiplyadd(_:_:_:_:)-8n6xy"
---

# SparseMultiplyAdd(_:_:_:_:)

Performs the multiply operation y += alpha * Ax on a vector of single-precision, floating-point values.

## Declaration

```swift
func SparseMultiplyAdd(_ alpha: Float, _ A: SparseMatrix_Float, _ x: DenseVector_Float, _ y: DenseVector_Float)
```

## Parameters

- `alpha`: The scalar value alpha in y += alpha * Ax.
- `A`: The sparse matrix A in y += Ax.
- `x`: The dense vector x in y += Ax.
- `y`: The dense vector y in y += Ax.

## Discussion

Discussion Use this function to multiply a scalar by a sparse matrix, then by a dense vector, and accumulate the result. The following equation is an example of a matrix-vector multiplication where the matrix is sparse:

Call SparseMultiplyAdd(_:_:_:_:) 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: [Float] = [1.0, 4.0, 13.0, 16.0]

/// The _A_ in _y+=Ax_. let A = SparseConvertFromCoordinate(rowCount, columnCount,                                     blockCount, blockSize,                                     SparseAttributes_t(),                                     rowIndices, columnIndices,                                     data) defer {     SparseCleanup(A) }

/// The values for _x_ in _y+=Ax_. var xValues: [Float] = [10.0, -1.0, -1.0, 10.0]

var yValues: [Float] = [1.0, 1.0, 1.0, 1.0]

let alpha: Float = 2.0

/// The values for _y_ in _y+=Ax_. yValues.withUnsafeMutableBufferPointer { yValuesPtr in          xValues.withUnsafeMutableBufferPointer { xValuesPtr in         /// The _x_ in _y+=Ax_.         let x = DenseVector_Float(count: 4,                                   data: xValuesPtr.baseAddress!)                  /// The _y_ in _y+=Ax_.         let y = DenseVector_Float(count: 4,                                   data: yValuesPtr.baseAddress!)                  SparseMultiplyAdd(alpha, A, x, y)     } }

/// On return, `yValues` contains: ///      `[ 281.0, 1.0, 1.0, 401.0 ]`

## See Also

### Multiply-add functions

- [SparseMultiplyAdd(_:_:_:)](accelerate/sparsemultiplyadd(_:_:_:)-7iuo9.md)
- [SparseMultiplyAdd(_:_:_:)](accelerate/sparsemultiplyadd(_:_:_:)-ineu.md)
- [SparseMultiplyAdd(_:_:_:_:)](accelerate/sparsemultiplyadd(_:_:_:_:)-3oa6n.md)