subroutine aptvaxc (au, av, bu, bv, np, tol, cw, nerr) ccbeg. cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c SUBROUTINE APTVAXC c c call aptvaxc (au, av, bu, bv, np, tol, cw, nerr) c c Version: aptvaxc Updated 1990 November 26 10:00. c aptvaxc Originated 1989 November 2 14:10. c c Author: Arthur L. Edwards, LLNL, L-298, Telephone (925) 422-4123. c c c Purpose: To find the vector products cw of the np 2-D vector pairs c a = (au, av) and b = (bu, bv). Vectors a and b are in the uv c plane. The directions u, v, and w are orthogonal. Any values c of cw less than the estimated error in their calculation, based c on tol, will be truncated to zero. Flag nerr indicates any c input error. c c With no truncation, c cw = au * bv - av * bu. c c Input: au, av, bu, bv, np, tol. c c Output: cw, nerr. c c Glossary: c c au, av Input The u and v components of input vector "a". Size np. c The w components are zero. Directions u, v and w c are orthogonal. c c bu, bv Input The u and v components of input vector "b". Size np. c The w components are zero. c c cw Output The w component of output vector "c". Size np. c Vector (cross) product of vectors "a" and "b". c The u and v components are zero. c Equal to the area of the parallelogram with sides c "a" and "b". c Positive if the angle from "a" to "b", in the uv c plane, is in the range from zero to 180 degrees. c Truncated to zero if less than the estimated error in c their calculation. See tol. c c nerr Output Indicates an input error, if not 0. c 1 if np is not positive. c c np Input Size of arrays au, av, bu, bv, cw. c c tol Input Numerical tolerance limit. c On Cray computers, recommend 1.e-5 to 1.e-11. c cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc ccend. c.... Dimensioned arguments. c---- Component u of input vector "a". dimension au (1) c---- Component v of input vector "a". dimension av (1) c---- Component u of input vector "b". dimension bu (1) c---- Component v of input vector "b". dimension bv (1) c---- Component w of output vector "c". dimension cw (1) c.... Local variables. c---- Index, 1 to np. common /laptvaxc/ n c---- Estimated error in cw. common /laptvaxc/ cwerr cbugc***DEBUG begins. cbug 9901 format (/ 'aptvaxc finding vector product of vectors:' / 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 vector products. c---- Loop over vectors. do 110 n = 1, np cw(n) = au(n) * bv(n) - av(n) * bu(n) c---- End of loop over vectors. 110 continue c---- Truncate small components to zero. if (tol .gt. 0.0) then c---- Loop over vectors. do 120 n = 1, np cwerr = 2.0 * tol * (abs (au(n) * bv(n)) + & abs (av(n) * bu(n))) if (abs (cw(n)) .lt. cwerr) then cw(n) = 0.0 endif c---- End of loop over vectors. 120 continue c---- Tested tol. endif cbugc***DEBUG begins. cbug 9902 format (/ 'aptvaxc results:' / cbug & (i3,' cw= ',1pe22.14)) cbug write ( 3, 9902) (n, cw(n), n = 1, np) cbugc***DEBUG ends. 210 return c.... End of subroutine aptvaxc. (+1 line.) end UCRL-WEB-209832