arpack.py 文件源码

def _augmented_orthonormal_cols(x, k):
    # extract the shape of the x array
    n, m = x.shape
    # create the expanded array and copy x into it
    y = np.empty((n, m+k), dtype=x.dtype)
    y[:, :m] = x
    # do some modified gram schmidt to add k random orthonormal vectors
    for i in range(k):
        # sample a random initial vector
        v = np.random.randn(n)
        if np.iscomplexobj(x):
            v = v + 1j*np.random.randn(n)
        # subtract projections onto the existing unit length vectors
        for j in range(m+i):
            u = y[:, j]
            v -= (np.dot(v, u.conj()) / np.dot(u, u.conj())) * u
        # normalize v
        v /= np.sqrt(np.dot(v, v.conj()))
        # add v into the output array
        y[:, m+i] = v
    # return the expanded array
    return y