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C/MEMBR ADD NAME=PYTHAG,SSI=0
c Copyright INRIA
double precision function pythag(a,b)
c!but
c pythag calcule (a**2+b**2)**(1/2), par une methode iterative
c!liste d'appel
c double precision function pythag(a,b)
c double precision a,b
c!
double precision a,b,dlamch
double precision p,q,r,s,t
c --------testing Nans
if (isanan(a).eq.1) then
pythag=a
return
endif
if (isanan(b).eq.1) then
pythag=b
return
endif
c --------testing Inf
if ( a.ge.dlamch('o').or.-a.ge.dlamch('o')) then
pythag = abs(a)
return
endif
if ( b.ge.dlamch('o').or.-b.ge.dlamch('o')) then
pythag = abs(b)
return
endif
c --------generic case
p = max(abs(a),abs(b))
q = min(abs(a),abs(b))
if (q .eq. 0.0d+0) go to 20
10 r = (q/p)**2
t = 4.0d+0 + r
if (t .eq. 4.0d+0) go to 20
s = r/t
p = p + 2.0d+0*p*s
q = q*s
go to 10
20 pythag = p
return
end
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