subroutine aptvdic (au, av, bu, bv, np, tol, du, dv, dab, nerr)
ccbeg.
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c
c SUBROUTINE APTVDIC
c
c call aptvdic (au, av, bu, bv, np, tol, du, dv, dab, nerr)
c
c Version: aptvdic Updated 1990 November 26 10:00.
c aptvdic Originated 1989 December 29 15:50.
c
c Author: Arthur L. Edwards, LLNL, L-298, Telephone (925) 422-4123.
c
c
c Purpose: To find, for each of the np sets of input data, the 2-D vector
c d = (du, dv) from point a = (au, av) to point b = (bu, bv),
c and its magnitude dab, the distance from "a" to "b", all in the
c uv plane. Directions u, v and w are orthogonal.
c Any component of vector "d" less than the estimated error in
c its calculation, based on tol, will be truncated to zero.
c Flag nerr indicates any input error.
c
c With no truncation, (du, dv) = (bu, bv) - (au, av),
c and distance dab = sqrt (du**2 + dv**2).
c
c Input: au, av, bu, bv, np, tol.
c
c Output: du, dv, dab, nerr.
c
c Glossary:
c
c au, av Input The u and v coordinates of point "a". Size np.
c The w coordinates are zero. Directions u, v and w
c are orthogonal.
c
c bu, bv Input The u and v coordinates of point "b". Size np.
c The w coordinates are zero.
c
c dab Output Distance between points "a" and "b", equal to
c the length of 2-D vector d = (du, dv). May be
c truncated to zero, if less than the estimated error
c in its calculation. See tol. Size np.
c
c du, dv Output The u and v components of 2-D vector "d". Size np.
c The w coordinates are zero.
c May be truncated to zero, if less than the estimated
c numerical error in their calculation based on tol.
c
c nerr Output Indicates an input error, if not 0.
c 1 if np is not positive.
c
c np Input The size of arrays au, av, bu, bv, dab, du, dv.
c
c tol Input Numerical tolerance limit. Used to truncate
c the components of 2-D vector d = (du, dv).
c On Cray computers, recommend 1.e-5 to 1.e-11.
c
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ccend.
c.... Dimensioned arguments.
c---- Coordinate u of point "a".
dimension au (1)
c---- Coordinate v of point "a".
dimension av (1)
c---- Coordinate u of point "b".
dimension bu (1)
c---- Coordinate v of point "b".
dimension bv (1)
c---- the distance from "a" to "b".
dimension dab (1)
c---- Component u of vector "d".
dimension du (1)
c---- Component v of vector "d".
dimension dv (1)
c.... Local variables.
c---- Estimated error in du.
common /laptvdic/ duerr
c---- Estimated error in dv.
common /laptvdic/ dverr
c---- Index in "a", "b", "d", dab.
common /laptvdic/ n
cbugc***DEBUG begins.
cbug 9901 format (/ 'aptvdic finding distance between points:' /
cbug & (i3,' au,av= ',1p2e22.14 /
cbug & ' bu,bv= ',1p2e22.14))
cbug write ( 3, 9901) (n, au(n), av(n), bu(n), bv(n), n = 1, np)
cbugc***DEBUG ends.
c.... Initialize.
nerr = 0
c.... Test for input errors.
if (np .le. 0) then
nerr = 1
go to 210
endif
c.... Find the components of the distance vectors.
c---- Loop over points or vectors.
do 110 n = 1, np
du(n) = bu(n) - au(n)
dv(n) = bv(n) - av(n)
c---- End of loop over points or vectors.
110 continue
c.... See if the truncation error option is to be used.
c---- Test and adjust du, dv.
if (tol .gt. 0.0) then
c---- Loop over points or vectors.
do 120 n = 1, np
duerr = tol * (abs (au(n)) + abs (bu(n)))
if (abs (du(n)) .lt. duerr) then
du(n) = 0.0
endif
dverr = tol * (abs (av(n)) + abs (bv(n)))
if (abs (dv(n)) .lt. dverr) then
dv(n) = 0.0
endif
c---- End of loop over points or vectors.
120 continue
c---- Tested tol.
endif
c.... Find the magnitudes of the distance vectors.
c---- Loop over points or vectors.
do 130 n = 1, np
dab(n) = sqrt (du(n)**2 + dv(n)**2)
c---- End of loop over points or vectors.
130 continue
cbugc***DEBUG begins.
cbug 9902 format (/ 'aptvdic results:' /
cbug & (i3,' du,dv,dab=',1p3e22.14))
cbug write ( 3, 9902) (n, du(n), dv(n), dab(n), n = 1, np)
cbugc***DEBUG ends.
210 return
c.... End of subroutine aptvdic. (+1 line.)
end
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