  We introduce a simplified version of the steady-state ab initio laser theory
for calculating the effects of mode competition in continuous wave lasers using
the passive cavity resonances. This new theory harnesses widely available
numerical methods that can efficiently calculate the passive cavity resonances,
with negligible additional computational overhead. Using this theory, we
demonstrate that the pump profile of the laser cavity can be optimized both for
highly multi-mode and single-mode emission. An open source implementation of
this method has been made available.
