utils.py 文件源码

def nullspace(A, eps=1e-15):
    u, s, vh = sp.linalg.svd(A,full_matrices=1,compute_uv=1)
    # Pad so that we get the nullspace of a wide matrix. 
    N = A.shape[1]
    K = s.shape[0]
    if K < N:
        s[K+1:N] = 0
        s2 = np.zeros((N))
        s2[0:K] = s
        s = s2
    null_mask = (s <= eps)
    null_space = sp.compress(null_mask, vh, axis=0)
    return sp.transpose(null_space)

# return smallest singular vector of A (or the nullspace if A is 2x3)