'Initialize the data structures needed for the VSIDS heuristic.'

def _vsids_init(self):

    self.lit_heap = []
    self.lit_scores = {}
    for var in range(1, len(self.variable_set)):
        self.lit_scores[var] = float((- self.occurrence_count[var]))
        self.lit_scores[(- var)] = float((- self.occurrence_count[(- var)]))
        heappush(self.lit_heap, (self.lit_scores[var], var))
        heappush(self.lit_heap, (self.lit_scores[(- var)], (- var)))
