---
title: "cblas_drotmg(_:_:_:_:_:)"
framework: accelerate
role: symbol
role_heading: Function
path: "accelerate/cblas_drotmg(_:_:_:_:_:)"
---

# cblas_drotmg(_:_:_:_:_:)

Generates a modified Givens rotation matrix.

## Declaration

```swift
func cblas_drotmg(_ D1: UnsafeMutablePointer<Double>, _ D2: UnsafeMutablePointer<Double>, _ B1: UnsafeMutablePointer<Double>, _ B2: Double, _ P: UnsafeMutablePointer<Double>)
```

## Parameters

- `D1`: Scaling factor D1.
- `D2`: Scaling factor D2.
- `B1`: Scaling factor B1.
- `B2`: Scaling factor B2.
- `P`: A 5-element vector: -2.0: matrix H contains the identity matrix. -1.0: matrix H is identical to matrix SH (defined by the remaining values in the vector). 0.0: H[1,2] and H[2,1] are obtained from matrix SH. The remaining values are both 1.0. 1.0: H[1,1] and H[2,2] are obtained from matrix SH. H[1,2] is 1.0. H[2,1] is -1.0.

## Discussion

Discussion The resulting matrix zeroes the second component of the vector (sqrt(D1)*B1, sqrt(SD2)*B2). 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.

## See Also

### Double-precision float matrix functions

- [cblas_dasum(_:_:_:)](accelerate/cblas_dasum(_:_:_:).md)
- [cblas_daxpy(_:_:_:_:_:_:)](accelerate/cblas_daxpy(_:_:_:_:_:_:).md)
- [cblas_dcopy(_:_:_:_:_:)](accelerate/cblas_dcopy(_:_:_:_:_:).md)
- [cblas_dgbmv(_:_:_:_:_:_:_:_:_:_:_:_:_:_:)](accelerate/cblas_dgbmv(_:_:_:_:_:_:_:_:_:_:_:_:_:_:).md)
- [cblas_dgemm(_:_:_:_:_:_:_:_:_:_:_:_:_:_:)](accelerate/cblas_dgemm(_:_:_:_:_:_:_:_:_:_:_:_:_:_:).md)
- [cblas_dgemv(_:_:_:_:_:_:_:_:_:_:_:_:)](accelerate/cblas_dgemv(_:_:_:_:_:_:_:_:_:_:_:_:).md)
- [cblas_dger(_:_:_:_:_:_:_:_:_:_:)](accelerate/cblas_dger(_:_:_:_:_:_:_:_:_:_:).md)
- [cblas_dnrm2(_:_:_:)](accelerate/cblas_dnrm2(_:_:_:).md)
- [cblas_drot(_:_:_:_:_:_:_:)](accelerate/cblas_drot(_:_:_:_:_:_:_:).md)
- [cblas_drotg(_:_:_:_:)](accelerate/cblas_drotg(_:_:_:_:).md)
- [cblas_drotm(_:_:_:_:_:_:)](accelerate/cblas_drotm(_:_:_:_:_:_:).md)
- [cblas_dsbmv(_:_:_:_:_:_:_:_:_:_:_:_:)](accelerate/cblas_dsbmv(_:_:_:_:_:_:_:_:_:_:_:_:).md)
- [cblas_dscal(_:_:_:_:)](accelerate/cblas_dscal(_:_:_:_:).md)
- [cblas_dspmv(_:_:_:_:_:_:_:_:_:_:)](accelerate/cblas_dspmv(_:_:_:_:_:_:_:_:_:_:).md)
- [cblas_dspr(_:_:_:_:_:_:_:)](accelerate/cblas_dspr(_:_:_:_:_:_:_:).md)