Solves the set of n linearequations Ax = b. (LUBKSB must be used with the procedure LUDCMP to do this.)
The LU decomposition of a matrix, created by LUDCMP. Parameter a is not modified by calling this procedure.index
A vector, created by LUDCMP, containing the row permutations effected by the partial pivoting.b
On input, b contains the vector on the right-hand side of the equation. Must be of data type FLOAT; other data types will cause incorrect output.
On output, b is replaced by the solution, vector x.
Function INNER_PROD, v1, v2 IF N_ELEMENTS(v1) NE 3 THEN goto, error1 IF N_ELEMENTS(v2) NE 3 THEN goto, error1 sum = 0.0 FOR i=0, 2 DO BEGIN
sum = sum + v1(i) * v2(i)
END RETURN, sum error1:
PRINT, 'vectors not 3d'
RETURN, 0
END arr = FINDGEN(3, 3) arr(*, 0) = [1.0, -1.0, 3.0] arr(*, 1) = [2.0, 1.0, 3.0] arr(*, 2) = [3.0, 3.0, 1.0]
rightvec = [3.0, 0.0, 6.0]
PRINT, ' '
PRINT, 'solving system '
PRINT, arr, ' * [x,y,z] = ', rightvec
PRINT, ' '
PRINT, ' '
tarr = arr
rvec = rightvec
LUDCMP, tarr, index, b
LUBKSB, tarr, index, rvec
PRINT, '... solution for ', rightvec,' $
is ', rvec
s1 = rvec
PRINT, ' '
PRINT, ' '
PRINT, INNER_PROD(arr(0,*), s1)
PRINT, INNER_PROD(arr(1,*), s1)
PRINT, INNER_PROD(arr(2,*), s1)
PRINT, ' '
PRINT, ' '
END
