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*DECK PYTHAG
REAL FUNCTION PYTHAG (A, B)
C***BEGIN PROLOGUE PYTHAG
C***SUBSIDIARY
C***PURPOSE Compute the complex square root of a complex number without
C destructive overflow or underflow.
C***LIBRARY SLATEC
C***TYPE SINGLE PRECISION (PYTHAG-S)
C***AUTHOR (UNKNOWN)
C***DESCRIPTION
C
C Finds sqrt(A**2+B**2) without overflow or destructive underflow
C
C***SEE ALSO EISDOC
C***ROUTINES CALLED (NONE)
C***REVISION HISTORY (YYMMDD)
C 811101 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900402 Added TYPE section. (WRB)
C***END PROLOGUE PYTHAG
REAL A,B
C
REAL P,Q,R,S,T
C***FIRST EXECUTABLE STATEMENT PYTHAG
P = MAX(ABS(A),ABS(B))
Q = MIN(ABS(A),ABS(B))
IF (Q .EQ. 0.0E0) GO TO 20
10 CONTINUE
R = (Q/P)**2
T = 4.0E0 + R
IF (T .EQ. 4.0E0) GO TO 20
S = R/T
P = P + 2.0E0*P*S
Q = Q*S
GO TO 10
20 PYTHAG = P
RETURN
END
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