68 lines
1.9 KiB
Fortran
68 lines
1.9 KiB
Fortran
REAL FUNCTION SCNRM2F( N, X, INCX )
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* .. Scalar Arguments ..
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INTEGER INCX, N
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* .. Array Arguments ..
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COMPLEX X( * )
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* ..
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*
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* SCNRM2 returns the euclidean norm of a vector via the function
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* name, so that
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*
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* SCNRM2 := sqrt( conjg( x' )*x )
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*
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*
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*
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* -- This version written on 25-October-1982.
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* Modified on 14-October-1993 to inline the call to CLASSQ.
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* Sven Hammarling, Nag Ltd.
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*
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*
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* .. Parameters ..
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REAL ONE , ZERO
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PARAMETER ( ONE = 1.0E+0, ZERO = 0.0E+0 )
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* .. Local Scalars ..
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INTEGER IX
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REAL NORM, SCALE, SSQ, TEMP
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* .. Intrinsic Functions ..
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INTRINSIC ABS, AIMAG, REAL, SQRT
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* ..
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* .. Executable Statements ..
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IF( N.LT.1 .OR. INCX.LT.1 )THEN
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NORM = ZERO
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ELSE
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SCALE = ZERO
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SSQ = ONE
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* The following loop is equivalent to this call to the LAPACK
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* auxiliary routine:
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* CALL CLASSQ( N, X, INCX, SCALE, SSQ )
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*
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DO 10, IX = 1, 1 + ( N - 1 )*INCX, INCX
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IF( REAL( X( IX ) ).NE.ZERO )THEN
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TEMP = ABS( REAL( X( IX ) ) )
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IF( SCALE.LT.TEMP )THEN
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SSQ = ONE + SSQ*( SCALE/TEMP )**2
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SCALE = TEMP
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ELSE
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SSQ = SSQ + ( TEMP/SCALE )**2
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END IF
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END IF
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IF( AIMAG( X( IX ) ).NE.ZERO )THEN
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TEMP = ABS( AIMAG( X( IX ) ) )
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IF( SCALE.LT.TEMP )THEN
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SSQ = ONE + SSQ*( SCALE/TEMP )**2
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SCALE = TEMP
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ELSE
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SSQ = SSQ + ( TEMP/SCALE )**2
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END IF
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END IF
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10 CONTINUE
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NORM = SCALE * SQRT( SSQ )
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END IF
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*
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SCNRM2F = NORM
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RETURN
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*
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* End of SCNRM2.
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*
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END
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