# vDSP_zmms Subtracts a single-precision complex matrix from the product of two single-precision complex matrices. ``` extern void vDSP_zmms(const DSPSplitComplex *__A, vDSP_Stride __IA, const DSPSplitComplex *__B, vDSP_Stride __IB, const DSPSplitComplex *__C, vDSP_Stride __IC, const DSPSplitComplex *__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 The following code subtracts the matrix `c` from the product of matrices `a` and `b`, and writes the result to matrix `d`: ```swift /// 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.allocate(capacity: Int(m * p)) _ = aReal.initialize(from: [1, 2, 3]) let aImag = UnsafeMutableBufferPointer.allocate(capacity: Int(m * p)) _ = aImag.initialize(from: [2, 3, 4]) var a = DSPDoubleSplitComplex(realp: aReal.baseAddress!, imagp: aImag.baseAddress!) // `p` rows x `n` columns. let bReal = UnsafeMutableBufferPointer.allocate(capacity: Int(p * n)) _ = bReal.initialize(from: [4, 5, 6]) let bImag = UnsafeMutableBufferPointer.allocate(capacity: Int(p * n)) _ = bImag.initialize(from: [5, 6, 7]) var b = DSPDoubleSplitComplex(realp: bReal.baseAddress!, imagp: bImag.baseAddress!) // `m` rows x `n` columns. let cReal = UnsafeMutableBufferPointer.allocate(capacity: Int(m * n)) _ = cReal.initialize(from: [4]) let cImag = UnsafeMutableBufferPointer.allocate(capacity: Int(m * n)) _ = cImag.initialize(from: [5]) var c = DSPDoubleSplitComplex(realp: cReal.baseAddress!, imagp: cImag.baseAddress!) // `m` rows x `n` columns. let dReal = UnsafeMutableBufferPointer.allocate(capacity: Int(m * n)) let dImag = UnsafeMutableBufferPointer.allocate(capacity: Int(m * n)) var d = DSPDoubleSplitComplex(realp: dReal.baseAddress!, imagp: dImag.baseAddress!) vDSP_zmmsD(&a, 1, &b, 1, &c, 1, &d, 1, m, n, p) print(Array(dReal)) // Prints "[-28.0]". print(Array(dImag)) // Prints "[80.0]". ``` --- Copyright © 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)