28 lines
635 B
FortranFixed
28 lines
635 B
FortranFixed
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subroutine srotgf(sa,sb,c,s)
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c
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c construct givens plane rotation.
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c jack dongarra, linpack, 3/11/78.
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c
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real sa,sb,c,s,roe,scale,r,z
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c
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roe = sb
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if( abs(sa) .gt. abs(sb) ) roe = sa
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scale = abs(sa) + abs(sb)
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if( scale .ne. 0.0 ) go to 10
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c = 1.0
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s = 0.0
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r = 0.0
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z = 0.0
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go to 20
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10 r = scale*sqrt((sa/scale)**2 + (sb/scale)**2)
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r = sign(1.0,roe)*r
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c = sa/r
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s = sb/r
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z = 1.0
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if( abs(sa) .gt. abs(sb) ) z = s
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if( abs(sb) .ge. abs(sa) .and. c .ne. 0.0 ) z = 1.0/c
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20 sa = r
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sb = z
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return
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end
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