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Diffstat (limited to 'src/fortran/lapack/dlapy3.f')
| -rw-r--r-- | src/fortran/lapack/dlapy3.f | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/src/fortran/lapack/dlapy3.f b/src/fortran/lapack/dlapy3.f new file mode 100644 index 0000000..2b47bb4 --- /dev/null +++ b/src/fortran/lapack/dlapy3.f @@ -0,0 +1,56 @@ + DOUBLE PRECISION FUNCTION DLAPY3( X, Y, Z ) +* +* -- LAPACK auxiliary routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + DOUBLE PRECISION X, Y, Z +* .. +* +* Purpose +* ======= +* +* DLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause +* unnecessary overflow. +* +* Arguments +* ========= +* +* X (input) DOUBLE PRECISION +* Y (input) DOUBLE PRECISION +* Z (input) DOUBLE PRECISION +* X, Y and Z specify the values x, y and z. +* +* ===================================================================== +* +* .. Parameters .. + DOUBLE PRECISION ZERO + PARAMETER ( ZERO = 0.0D0 ) +* .. +* .. Local Scalars .. + DOUBLE PRECISION W, XABS, YABS, ZABS +* .. +* .. Intrinsic Functions .. + INTRINSIC ABS, MAX, SQRT +* .. +* .. Executable Statements .. +* + XABS = ABS( X ) + YABS = ABS( Y ) + ZABS = ABS( Z ) + W = MAX( XABS, YABS, ZABS ) + IF( W.EQ.ZERO ) THEN +* W can be zero for max(0,nan,0) +* adding all three entries together will make sure +* NaN will not disappear. + DLAPY3 = XABS + YABS + ZABS + ELSE + DLAPY3 = W*SQRT( ( XABS / W )**2+( YABS / W )**2+ + $ ( ZABS / W )**2 ) + END IF + RETURN +* +* End of DLAPY3 +* + END |