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# vDSP_vsbsmD

Calculates the double-precision element-wise product of the difference of two vectors and a scalar value, using the specified stride.

```
extern void vDSP_vsbsmD(const double *__A, vDSP_Stride __IA, const double *__B, vDSP_Stride __IB, const double *__C, double *__D, vDSP_Stride __ID, vDSP_Length __N);
```

## Parameters

`__A`

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

`__IA`

The distance between the elements in the input vector `A`.

`__B`

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

`__IB`

The distance between the elements in the input vector `B`.

`__C`

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

`__D`

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

`__ID`

The distance between the elements in the output vector `D`.

`__N`

The number of elements that the function processes.

## 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-4387352@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 = 5
    
    let d = [Double](unsafeUninitializedCapacity: count) {
        buffer, initializedCount in
        
        vDSP_vsbsmD(a, stride,
                    b, stride,
                    [c],
                    buffer.baseAddress!, stride,
                    vDSP_Length(count))
        
        initializedCount = count
    }
    
    // Prints "[-45.0, -90.0, -135.0, -180.0, -225.0]".
    print(d)
```

---

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