<!--
{
  "availability" : [
    "iOS: 4.0.0 -",
    "iPadOS: 4.0.0 -",
    "macCatalyst: 13.1.0 -",
    "macOS: 10.2.0 -",
    "tvOS: -",
    "visionOS: 1.0.0 -",
    "watchOS: 2.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "Accelerate",
  "identifier" : "/documentation/Accelerate/vDSP_vmulD",
  "metadataVersion" : "0.1.0",
  "role" : "Function",
  "symbol" : {
    "kind" : "Function",
    "modules" : [
      "Accelerate"
    ],
    "preciseIdentifier" : "c:@F@vDSP_vmulD"
  },
  "title" : "vDSP_vmulD"
}
-->

# vDSP_vmulD

Calculates the double-precision element-wise product of two vectors, using the specified stride.

```
extern void vDSP_vmulD(const double *__A, vDSP_Stride __IA, const double *__B, vDSP_Stride __IB, double *__C, vDSP_Stride __IC, vDSP_Length __N);
```

## Parameters

`__A`

The first input vector, `A`.

`__IA`

The distance between the elements in the first input vector.

`__B`

The second input vector, `B`.

`__IB`

The distance between the elements in the second input vector.

`__C`

The output vector, `C`.

`__IC`

The distance between the elements in the output vector.

`__N`

The number of elements that the function processes.

## Discussion

This function calculates the products of the first `N` elements of input vectors `A` and `B`, and writes the result to output vector `C`.

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

![A diagram showing the operation of this function. There are three rows. The top row represents the input vectors, A and B, with three boxes of each. The middle row represents the operation as three boxes with multiplication signs. The bottom row represents the output vector C as three boxes. The diagram has connecting lines from the input vectors to the operation, and from the operation to the output vectors.](images/com.apple.accelerate/media-4336910@2x.png)

The following code shows an example of using this function:

```swift
    let stride = 1
    let count = 5
    
    let a: [Double] = [ 1,  2,  3,  4,  5]
    let b: [Double] = [10, 20, 30, 40, 50]
    
    let c = [Double](unsafeUninitializedCapacity: count) {
        buffer, initializedCount in
        
        vDSP_vmulD(a, stride,
                   b, stride,
                   buffer.baseAddress!, stride,
                   vDSP_Length(count))
        
        initializedCount = count
    }
    
    // Prints "[10.0, 40.0, 90.0, 160.0, 250.0]".
    print(c)
```

---

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)