Select default sparse direct solver to be used.
useUmfpack : bool, optional
Use UMFPACK over SuperLU. Has effect only if scikits.umfpack is installed. Default: True
The default sparse solver is umfpack when available (scikits.umfpack is installed). This can be changed by passing useUmfpack = False, which then causes the always present SuperLU based solver to be used.
Umfpack requires a CSR/CSC matrix to have sorted column/row indices. If sure that the matrix fulfills this, pass assumeSortedIndices=True to gain some speed.