LWORK Query

If in doubt about the amount of workspace to supply to an LAPACK routine, the user may choose to supply LWORK=-1 and use the returned value in WORK(1) as the correct value for LWORK. Setting LWORK=-1 does not invoke an error message from XERBLA and is defined as a global query.

The routines xGEESX and xGGESX are the only exceptions to this rule. For these routines, the value of LWORK is dependent upon the dimension of the invariant subspace (SDIM), and is not known on entry to the routine.