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Diffstat (limited to '2.3-1/src/fortran/blas/dnrm2.f')
| -rw-r--r-- | 2.3-1/src/fortran/blas/dnrm2.f | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/2.3-1/src/fortran/blas/dnrm2.f b/2.3-1/src/fortran/blas/dnrm2.f new file mode 100644 index 00000000..119d0477 --- /dev/null +++ b/2.3-1/src/fortran/blas/dnrm2.f @@ -0,0 +1,60 @@ + DOUBLE PRECISION FUNCTION DNRM2 ( N, X, INCX ) +* .. Scalar Arguments .. + INTEGER INCX, N +* .. Array Arguments .. + DOUBLE PRECISION X( * ) +* .. +* +* 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 .. + INTEGER IX + DOUBLE PRECISION ABSXI, NORM, SCALE, SSQ +* .. Intrinsic Functions .. + INTRINSIC ABS, SQRT +* .. +* .. Executable Statements .. + 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 |