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DOUBLE PRECISION FUNCTION DNRM2(N,X,INCX)
* .. Scalar Arguments ..
INTEGER INCX,N
* ..
* .. Array Arguments ..
DOUBLE PRECISION X(*)
* ..
*
* Purpose
* =======
*
* DNRM2 returns the euclidean norm of a vector via the function
* name, so that
*
* DNRM2 := sqrt( x'*x )
*
*
* -- This version written on 25-October-1982.
* Modified on 14-October-1993 to inline the call to DLASSQ.
* Sven Hammarling, Nag Ltd.
*
*
* .. Parameters ..
DOUBLE PRECISION ONE,ZERO
PARAMETER (ONE=1.0D+0,ZERO=0.0D+0)
* ..
* .. Local Scalars ..
DOUBLE PRECISION ABSXI,NORM,SCALE,SSQ
INTEGER IX
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS,SQRT
* ..
IF (N.LT.1 .OR. INCX.LT.1) THEN
NORM = ZERO
ELSE IF (N.EQ.1) THEN
NORM = ABS(X(1))
ELSE
SCALE = ZERO
SSQ = ONE
* The following loop is equivalent to this call to the LAPACK
* auxiliary routine:
* CALL DLASSQ( N, X, INCX, SCALE, SSQ )
*
DO 10 IX = 1,1 + (N-1)*INCX,INCX
IF (X(IX).NE.ZERO) THEN
ABSXI = ABS(X(IX))
IF (SCALE.LT.ABSXI) THEN
SSQ = ONE + SSQ* (SCALE/ABSXI)**2
SCALE = ABSXI
ELSE
SSQ = SSQ + (ABSXI/SCALE)**2
END IF
END IF
10 CONTINUE
NORM = SCALE*SQRT(SSQ)
END IF
*
DNRM2 = NORM
RETURN
*
* End of DNRM2.
*
END
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