WDpbsv WDposv WDptsv WDsysv

WDptsv() Function WDptsv ( N As  Long, D As  Variant, E As  Variant, B As  Variant, Optional Nrhs As  Long = 1  ) Solution to system of linear equations AX = B for a symmetric positive definite tridiagonal matrix Purpose WDptsv computes the solution to a real system of linear equations A * X = B, where A is an N x N symmetric positive definite tridiagonal matrix, and X and B are N x Nrhs matrices. A is factored as A = L*D*L^T, and the factored form of A is then used to solve the system of equations. Returns N+2 x Nrhs Column 1 Column 2 . . . Column Nrhs Rows 1 to N Solution matrix X Row N+1 Reciprocal condition number 0 . . . 0 Row N+2 Return code 0 . . . 0 Return code. = 0: Successful exit. = i > 0: The leading minor of order i of A is not positive definite, so the factorization could not be completed, and the solution has not been computed. Parameters [in] N Number of linear equations, i.e., order of the matrix A. (N >= 1) [in] D (N) Diagonal elements of the N x N coefficient matrix A. [in] E (N-1) Subdiagonal elements of the N x N coefficient matrix A. [in] B (N x Nrhs) N x Nrhs right hand side matrix B. [in] Nrhs (Optional) Number of columns of right hand side matrix B. (Nrhs >= 1) (default = 1) Reference LAPACK Example Solve the system of linear equations Ax = B and estimate the reciprocal of the condition number (RCond) of A, where A is symmetric positive definite tridiagonal matrix and ( 2.58 -0.99 0 ) ( -1.1850 ) A = ( -0.99 0.69 -0.03 ), B = ( 0.1410 ) ( 0 -0.03 0.18 ) ( 0.1614 )