subroutine aptvaxb (ax, ay, az, bx, by, bz, np, tol, & cx, cy, cz, vlen, nerr) ccbeg. cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc c c SUBROUTINE APTVAXB c c call aptvaxb (ax, ay, az, bx, by, bz, np, tol, c & cx, cy, cz, vlen, nerr) c c Version: aptvaxb Updated 1990 November 26 10:00. c aptvaxb 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 c = (cx, cy, cz) of the np vector c pairs a = (ax, ay, az) and b = (bx, by, bz), and the magnitudes c vlen of the vectors "c". Any components of vector "c" less than c the estimated error in their calculation, based on tol, will be c truncated to zero. c Flag nerr indicates any input error. c c With no truncation, c cx = ay * bz - az * by c cy = az * bx - ax * bz c cz = ax * by - ay * bx. c c Input: ax, ay, az, bx, by, bz, np, tol. c c Output: cx, cy, cz, vlen, nerr. c c Glossary: c c ax,ay,az Input The x, y, z components of input vector "a". Size np. c c bx,by,bz Input The x, y, z components of input vector "b". Size np. c c cx,cy,cz Output The x, y, z components of output vector "c". Size np. c Vector (cross) product of vectors "a" and "b". 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 ax, ay, az, bx, by, bz, cx, cy, cz. c c tol Input Numerical tolerance limit. c On Cray computers, recommend 1.e-5 to 1.e-11. c c vlen Output Magnitude of the vector product "c". Size np. c cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc ccend. c.... Dimensioned arguments. c---- Component x of input vector "a". dimension ax (1) c---- Component y of input vector "a". dimension ay (1) c---- Component z of input vector "a". dimension az (1) c---- Component x of input vector "b". dimension bx (1) c---- Component y of input vector "b". dimension by (1) c---- Component z of input vector "b". dimension bz (1) c---- Component x of output vector "c". dimension cx (1) c---- Component y of output vector "c". dimension cy (1) c---- Component z of output vector "c". dimension cz (1) c---- Magnitude of vector "c". dimension vlen (1) c.... Local variables. c---- Index, 1 to np. common /laptvaxb/ n c---- Estimated error in cx. common /laptvaxb/ cxerr c---- Estimated error in cy. common /laptvaxb/ cyerr c---- Estimated error in cz. common /laptvaxb/ czerr cbugc***DEBUG begins. cbug 9901 format (/ 'aptvaxb finding vector product of vectors:' / cbug & (i3,' ax,ay,az=',1p3e22.14 / cbug & ' bx,by,bz=',1p3e22.14)) cbug write ( 3, 9901) (n, ax(n), ay(n), az(n), bx(n), by(n), bz(n), cbug & 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 cx(n) = ay(n) * bz(n) - az(n) * by(n) cy(n) = az(n) * bx(n) - ax(n) * bz(n) cz(n) = ax(n) * by(n) - ay(n) * bx(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 cxerr = 2.0 * tol * (abs (ay(n) * bz(n)) + & abs (az(n) * by(n))) if (abs (cx(n)) .lt. cxerr) then cx(n) = 0.0 endif cyerr = 2.0 * tol * (abs (az(n) * bx(n)) + & abs (ax(n) * bz(n))) if (abs (cy(n)) .lt. cyerr) then cy(n) = 0.0 endif czerr = 2.0 * tol * (abs (ax(n) * by(n)) + & abs (ay(n) * bx(n))) if (abs (cz(n)) .lt. czerr) then cz(n) = 0.0 endif c---- End of loop over vectors. 120 continue c---- Tested tol. endif c---- Loop over vectors. do 130 n = 1, np vlen(n) = sqrt (cx(n)**2 + cy(n)**2 + cz(n)**2) c---- End of loop over vectors. 130 continue cbugc***DEBUG begins. cbug 9902 format (/ 'aptvaxb results:' / cbug & (i3,' vlen= ',1pe22.14 / cbug & ' cx,cy,cz=',1p3e22.14)) cbug write ( 3, 9902) (n, vlen(n), cx(n), cy(n), cz(n), cbug & n = 1, np) cbugc***DEBUG ends. 210 return c.... End of subroutine aptvaxb. (+1 line.) end UCRL-WEB-209832