<!--
{
  "availability" : [
    "iOS: 16.4.0 -",
    "iPadOS: 16.4.0 -",
    "macCatalyst: 16.4.0 -",
    "macOS: 13.3.0 -",
    "tvOS: 16.4.0 -",
    "visionOS: 1.0.0 -",
    "watchOS: 9.4.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "Accelerate",
  "identifier" : "/documentation/Accelerate/cblas_izamax(_:_:_:)",
  "metadataVersion" : "0.1.0",
  "role" : "Function",
  "symbol" : {
    "kind" : "Function",
    "modules" : [
      "Accelerate"
    ],
    "preciseIdentifier" : "c:@F@cblas_izamax"
  },
  "title" : "cblas_izamax(_:_:_:)"
}
-->

# cblas_izamax(_:_:_:)

Returns the index of the element with the largest absolute value in a vector (double-precision complex).

```
func cblas_izamax(_ N: __LAPACK_int, _ X: OpaquePointer?, _ INCX: __LAPACK_int) -> __LAPACK_int
```

## Parameters

`N`

Number of elements in the vector.

`X`

The vector.

`INCX`

Stride within `X`. For example, if `incX` is 7, every 7th element is used.

## Return Value

Returns an index in the range 0..N-1 corresponding with the element with the largest absolute value.

## Discussion

> Important:
> Apple provides the BLAS and LAPACK libraries under the Accelerate framework to be in line with LAPACK 3.9.1. Starting with iOS 26, iPadOS 26, macOS 26, tvOS 26, visionOS 26, and watchOS 26, the libraries are in line with LAPACK 3.12.0. These new interfaces provide additional functionality, as well as a new ILP64 interface. To use the new interfaces, define `ACCELERATE_NEW_LAPACK` before including the Accelerate or vecLib headers. For ILP64 interfaces, also define `ACCELERATE_LAPACK_ILP64`. For Swift projects, specify `ACCELERATE_NEW_LAPACK=1` and `ACCELERATE_LAPACK_ILP64=1` as preprocessor macros in Xcode build settings under Apple Clang - Preprocessing > Preprocessor Macros.

---

Copyright &copy; 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)