# vDSP_zmmulD Performs an out-of-place multiplication of two double-precision complex matrices. ``` extern void vDSP_zmmulD(const DSPDoubleSplitComplex *__A, vDSP_Stride __IA, const DSPDoubleSplitComplex *__B, vDSP_Stride __IB, const DSPDoubleSplitComplex *__C, vDSP_Stride __IC, vDSP_Length __M, vDSP_Length __N, vDSP_Length __P); ``` ## Parameters `__A` The `M` x `P` left-hand side input matrix. `__IA` The distance between the elements in the left-hand side input matrix. `__B` The `P` x `N` right-hand side input matrix. `__IB` The distance between the elements in the right-hand side input matrix. `__C` The `M` x `N` output matrix. `__IC` The distance between the elements in the output matrix. `__M` The number of rows in matrices `A` and `C`. `__N` The number of columns in matrices `B` and `C`. `__P` The number of columns in matrix `A` and the number of rows in matrix `B`. ## Discussion The following code multiplies the matrices `a` and `b`, and writes the result to matrix `c`: ```swift // [ 4+5i, // [ 1+2i, 2+3i, 3+4i ] * 5+6i, = [ -24+85i ] // 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)) let cImag = UnsafeMutableBufferPointer.allocate(capacity: Int(m * n)) var c = DSPDoubleSplitComplex(realp: cReal.baseAddress!, imagp: cImag.baseAddress!) vDSP_zmmulD(&a, 1, &b, 1, &c, 1, m, n, p) print(Array(cReal)) // Prints "[-24.0]". print(Array(cImag)) // Prints "[85.0]". ``` --- 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)