It has an upper band width mu and a lower band width ml . On Return agb is the transformed matrix A of order n , containing the results of the factorization. Notes ipvt is not a permutation vector in the strict sense. It is used to record column interchanges in L due to partial pivoting and to improve performance. The entire lda by n array specified for agb must remain unchanged between calls to the factorization and solve subroutines.
L is a unit lower triangular band matrix.
U is an upper triangular band matrix. This factorization can then be used by SGBS or DGBS, respectively, to solve the system of equations. Error Conditions Resource Errors Unable to allocate internal work area. Computational Errors Matrix A is singular. The return code is set to 1.