```      SUBROUTINE SLARNV( IDIST, ISEED, N, X )
*
*  -- LAPACK auxiliary routine (version 3.1) --
*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
*     November 2006
*
*     .. Scalar Arguments ..
INTEGER            IDIST, N
*     ..
*     .. Array Arguments ..
INTEGER            ISEED( 4 )
REAL               X( * )
*     ..
*
*  Purpose
*  =======
*
*  SLARNV returns a vector of n random real numbers from a uniform or
*  normal distribution.
*
*  Arguments
*  =========
*
*  IDIST   (input) INTEGER
*          Specifies the distribution of the random numbers:
*          = 1:  uniform (0,1)
*          = 2:  uniform (-1,1)
*          = 3:  normal (0,1)
*
*  ISEED   (input/output) INTEGER array, dimension (4)
*          On entry, the seed of the random number generator; the array
*          elements must be between 0 and 4095, and ISEED(4) must be
*          odd.
*          On exit, the seed is updated.
*
*  N       (input) INTEGER
*          The number of random numbers to be generated.
*
*  X       (output) REAL array, dimension (N)
*          The generated random numbers.
*
*  Further Details
*  ===============
*
*  This routine calls the auxiliary routine SLARUV to generate random
*  real numbers from a uniform (0,1) distribution, in batches of up to
*  128 using vectorisable code. The Box-Muller method is used to
*  transform numbers from a uniform to a normal distribution.
*
*  =====================================================================
*
*     .. Parameters ..
REAL               ONE, TWO
PARAMETER          ( ONE = 1.0E+0, TWO = 2.0E+0 )
INTEGER            LV
PARAMETER          ( LV = 128 )
REAL               TWOPI
PARAMETER          ( TWOPI = 6.2831853071795864769252867663E+0 )
*     ..
*     .. Local Scalars ..
INTEGER            I, IL, IL2, IV
*     ..
*     .. Local Arrays ..
REAL               U( LV )
*     ..
*     .. Intrinsic Functions ..
INTRINSIC          COS, LOG, MIN, SQRT
*     ..
*     .. External Subroutines ..
EXTERNAL           SLARUV
*     ..
*     .. Executable Statements ..
*
DO 40 IV = 1, N, LV / 2
IL = MIN( LV / 2, N-IV+1 )
IF( IDIST.EQ.3 ) THEN
IL2 = 2*IL
ELSE
IL2 = IL
END IF
*
*        Call SLARUV to generate IL2 numbers from a uniform (0,1)
*        distribution (IL2 <= LV)
*
CALL SLARUV( ISEED, IL2, U )
*
IF( IDIST.EQ.1 ) THEN
*
*           Copy generated numbers
*
DO 10 I = 1, IL
X( IV+I-1 ) = U( I )
10       CONTINUE
ELSE IF( IDIST.EQ.2 ) THEN
*
*           Convert generated numbers to uniform (-1,1) distribution
*
DO 20 I = 1, IL
X( IV+I-1 ) = TWO*U( I ) - ONE
20       CONTINUE
ELSE IF( IDIST.EQ.3 ) THEN
*
*           Convert generated numbers to normal (0,1) distribution
*
DO 30 I = 1, IL
X( IV+I-1 ) = SQRT( -TWO*LOG( U( 2*I-1 ) ) )*
\$                       COS( TWOPI*U( 2*I ) )
30       CONTINUE
END IF
40 CONTINUE
RETURN
*
*     End of SLARNV
*
END

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