- 24.
- If
**FACT**= 'N', the matrix is factored as , where is a unit lower bidiagonal matrix and is a diagonal matrix. The factorization can also be regarded as having the form , where . - 25.
- If the leading minor of order of is not positive definite, then the routine returns with . Otherwise, the factored form of is used to estimate the condition number of . If the reciprocal of the condition number is less than machine precision, , where is the order of , is returned as a warning. However, the routine still goes on to solve for . Iterative refinement is applied to improve the computed solution.
- 26.
**LA_PTSVX**also optionally computes, for each solution vector , the estimated forward error bound and the componentwise relative backward error.

Susan Blackford 2001-08-19