---
name: "zlargv"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/zlargv/3lapack"
---

# zlargv(3lapack)

generates a vector of complex plane rotations with real cosines, determined by elements of the complex vectors x and y

## NAME

ZLARGV - generates a vector of complex plane rotations with real cosines, determined by elements of the complex vectors x and y

## SYNOPSIS

- SUBROUTINE ZLARGV(

  N, X, INCX, Y, INCY, C, INCC )

- INTEGER

  INCC, INCX, INCY, N

- DOUBLE

  PRECISION C( \* )

- COMPLEX\*16

  X( \* ), Y( \* )

## PURPOSE

ZLARGV generates a vector of complex plane rotations with real cosines, determined by elements of the complex vectors x and y. For i = 1,2,...,n\
\
    (        c(i)   s(i) ) ( x(i) ) = ( r(i) )\
\
    ( -conjg(s(i))  c(i) ) ( y(i) ) = (   0  )\
\
    where c(i)\*\*2 + ABS(s(i))\*\*2 = 1\
 The following conventions are used (these are the same as in ZLARTG, but differ from the BLAS1 routine ZROTG):\
\
    If y(i)=0, then c(i)=1 and s(i)=0.\
\
    If x(i)=0, then c(i)=0 and s(i) is chosen so that r(i) is real.

## ARGUMENTS

- N (input) INTEGER

  The number of plane rotations to be generated.

- X (input/output) COMPLEX\*16 array, dimension (1+(N-1)\*INCX)

  On entry, the vector x. On exit, x(i) is overwritten by r(i), for i = 1,...,n.

- INCX (input) INTEGER

  The increment between elements of X. INCX \> 0.

- Y (input/output) COMPLEX\*16 array, dimension (1+(N-1)\*INCY)

  On entry, the vector y. On exit, the sines of the plane rotations.

- INCY (input) INTEGER

  The increment between elements of Y. INCY \> 0.

- C (output) DOUBLE PRECISION array, dimension (1+(N-1)\*INCC)

  The cosines of the plane rotations.

- INCC (input) INTEGER

  The increment between elements of C. INCC \> 0.

## FURTHER DETAILS

6-6-96 - Modified with a new algorithm by W. Kahan and J. Demmel This version has a few statements commented out for thread safety (machine parameters are computed on each entry). 10 feb 03, SJH.