<!--
{
  "availability" : [
    "iOS: 13.0.0 -",
    "iPadOS: 13.0.0 -",
    "macCatalyst: -",
    "macOS: 10.15.0 -",
    "tvOS: 13.0.0 -",
    "visionOS: -",
    "watchOS: 6.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "Accelerate",
  "identifier" : "/documentation/Accelerate/vDSP/multiply(subtraction:_:)-3gxn3",
  "metadataVersion" : "0.1.0",
  "role" : "Type Method",
  "symbol" : {
    "kind" : "Type Method",
    "modules" : [
      "Accelerate"
    ],
    "preciseIdentifier" : "s:10Accelerate4vDSPO8multiply11subtraction_SaySdGx1a_q_1bt_SdtAA0A6BufferRzAaIR_Sd7ElementRtzSdAJRt_r0_lFZ"
  },
  "title" : "multiply(subtraction:_:)"
}
-->

# multiply(subtraction:_:)

Returns the double-precision element-wise product of the difference of two vectors and a scalar value.

```
static func multiply<T, U>(subtraction: (a: T, b: U), _ scalar: Double) -> [Double] where T : AccelerateBuffer, U : AccelerateBuffer, T.Element == Double, U.Element == Double
```

## Parameters

`subtraction`

A tuple that contains the vectors `A` and `B` in `D = (A - B) * C`.

`scalar`

The input scalar value `C` in `D = (A - B) * C`.

## Return Value

The output vector `D` in `D = (A - B) * C`.

## Discussion

This function calculates the element-wise difference of vectors `A` and `B`, multiplies the difference by scalar value `C`, and writes the result to vector `D`.

```swift
 for (n = 0; n < N; ++n)
    D[n] = (A[n] - B[n]) * C;
```

![A diagram showing the operation of this function. There are four rows. The top row represents the input vectors, A and B, with three boxes of each. The second row frepresents the operation that subtracts B from A, with three boxes, as well as the input scalar C with one box. The third row represents the multiplication operation as three boxes. The bottom row represents the output vector D as three boxes. The diagram has connecting lines from the input vectors to the operations, and from the operations to the output vector.  ](images/com.apple.accelerate/media-4387351@2x.png)

The following code shows an example of using this function:

```swift
    let a: [Double] = [ 1,  2,  3,  4,  5]
    let b: [Double] = [10, 20, 30, 40, 50]
    let c: Double = 5
    
    let d = vDSP.multiply(subtraction: (a, b),
                          c)
    
    // Prints "[-45.0, -90.0, -135.0, -180.0, -225.0]".
    print(d)
```

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)