def simple_reduce(self, rank):
        if self.collapsed is not None:
            return
        assert rank > 0
        while len(self.cs) > rank:
            del self.cs[0]
            del self.ds[0]
Reduce the rank of the matrix by dropping oldest vectors.
dataset/ETHPy150Open scipy/scipy/scipy/optimize/nonlin.py/LowRankMatrix.simple_reduce