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# vDSP_vsmsb

Calculates the single-precision element-wise difference of the product of a vector and a scalar value, and a vector, using the specified stride.

```
extern void vDSP_vsmsb(const float *__A, vDSP_Stride __IA, const float *__B, const float *__C, vDSP_Stride __IC, float *__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 scalar value `B` in `D = (A * B) - C`.

`__C`

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

`__IC`

The distance between the elements in the input vector `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 product of vector `A` and scalar value `B`, subtracts vector `C` from the product, and writes the result to vector `D`.

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

![A diagram showing the operation of this function. There are four rows. The top row represents the input vector A with three boxes, and the scalar value B with one box. The second row represents the operation that multiplies A and B, with three boxes, as well as the input vector C with three boxes. The third row represents the subtraction 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-4387385@2x.png)

The following code shows an example of using this function:

```swift
    let stride = 1
    let count = 5
    
    let a: [Float] = [ 1,  2,  3,  4,  5]
    let b: Float = 10
    let c: [Float] = [ 5,  4,  3,  2,  1]
    
    let d = [Float](unsafeUninitializedCapacity: count) {
        buffer, initializedCount in
        
        vDSP_vsmsb(a, stride,
                   [b],
                   c, stride,
                   buffer.baseAddress!, stride,
                   vDSP_Length(count))
        
        initializedCount = count
    }
    
    // Prints "[5.0, 16.0, 27.0, 38.0, 49.0]".
    print(d)
```

---

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