---
title: vDSP_zmmsD
framework: accelerate
role: symbol
role_heading: Function
path: accelerate/vdsp_zmmsd
---

# vDSP_zmmsD

Subtracts a double-precision complex matrix from the product of two double-precision complex matrices.

## Declaration

```occ
extern void vDSP_zmmsD(const DSPDoubleSplitComplex *__A, vDSP_Stride __IA, const DSPDoubleSplitComplex *__B, vDSP_Stride __IB, const DSPDoubleSplitComplex *__C, vDSP_Stride __IC, const DSPDoubleSplitComplex *__D, vDSP_Stride __ID, vDSP_Length __M, vDSP_Length __N, vDSP_Length __P);
```

## Parameters

- `__A`: The single-precision complex M x P input matrix a in d = (a * b) - c.
- `__IA`: The distance between the elements in the matrix A.
- `__B`: The single-precision complex P x N input matrix b in d = (a * b) - c.
- `__IB`: The distance between the elements in the matrix B.
- `__C`: The single-precision complex M x N input matrix c in d = (a * b) - c.
- `__IC`: The distance between the elements in the matrix C.
- `__D`: The single-precision complex M x N output matrix d in d = (a * b) - c.
- `__ID`: The distance between the elements in the matrix D.
- `__M`: The number of rows in matrices A, C, and D.
- `__N`: The number of columns in matrix B, C, and D.
- `__P`: The number of columns in matrix A and the number of rows in matrix B.

## Discussion

Discussion The following code subtracts the matrix c from the product of matrices a and b, and writes the result to matrix d:     /// Compute the following:     /// ```     ///                        [ 4+5i,     /// [ 1+2i, 2+3i, 3+4i ] *   5+6i,  - [ 4+5i ] = [ -28+80i ]     ///                          6+7i ]     /// ```          let m: vDSP_Length = 1     let n: vDSP_Length = 1     let p: vDSP_Length = 3          // `m` rows x `p` columns.     let aReal = UnsafeMutableBufferPointer<Float>.allocate(capacity: Int(m * p))     _ = aReal.initialize(from: [1, 2, 3])          let aImag = UnsafeMutableBufferPointer<Float>.allocate(capacity: Int(m * p))     _ = aImag.initialize(from: [2, 3, 4])          var a = DSPSplitComplex(realp: aReal.baseAddress!,                             imagp: aImag.baseAddress!)          // `p` rows x `n` columns.     let bReal = UnsafeMutableBufferPointer<Float>.allocate(capacity: Int(p * n))     _ = bReal.initialize(from: [4, 5, 6])          let bImag = UnsafeMutableBufferPointer<Float>.allocate(capacity: Int(p * n))     _ = bImag.initialize(from: [5, 6, 7])          var b = DSPSplitComplex(realp: bReal.baseAddress!,                             imagp: bImag.baseAddress!)          // `m` rows x `n` columns.     let cReal = UnsafeMutableBufferPointer<Float>.allocate(capacity: Int(m * n))     _ = cReal.initialize(from: [4])          let cImag = UnsafeMutableBufferPointer<Float>.allocate(capacity: Int(m * n))     _ = cImag.initialize(from: [5])          var c = DSPSplitComplex(realp: cReal.baseAddress!,                             imagp: cImag.baseAddress!)          // `m` rows x `n` columns.     let dReal = UnsafeMutableBufferPointer<Float>.allocate(capacity: Int(m * n))     let dImag = UnsafeMutableBufferPointer<Float>.allocate(capacity: Int(m * n))          var d = DSPSplitComplex(realp: dReal.baseAddress!,                             imagp: dImag.baseAddress!)          vDSP_zmms(&a, 1,               &b, 1,               &c, 1,               &d, 1,               m, n, p)          print(Array(dReal)) // Prints "[-28.0]".     print(Array(dImag)) // Prints "[80.0]".

## See Also

### Multiplying and subtracting complex matrices

- [vDSP_zmms](accelerate/vdsp_zmms.md)
- [vDSP_zmsm](accelerate/vdsp_zmsm.md)
- [vDSP_zmsmD](accelerate/vdsp_zmsmd.md)