def idd_snorm(m, n, matvect, matvec, its=<NUM_LIT:20>):
snorm, v = _id.idd_snorm(m, n, matvect, matvec, its)<EOL>return snorm<EOL>
Estimate spectral norm of a real matrix by the randomized power method.

:param m:
    Matrix row dimension.
:type m: int
:param n:
    Matrix column dimension.
:type n: int
:param matvect:
    Function to apply the matrix transpose to a vector, with call signature
    `y = matvect(x)`, where `x` and `y` are the input and output vectors,
    respectively.
:type matvect: function
:param matvec:
    Function to apply the matrix to a vector, with call signature
    `y = matvec(x)`, where `x` and `y` are the input and output vectors,
    respectively.
:type matvec: function
:param its:
    Number of power method iterations.
:type its: int

:return:
    Spectral norm estimate.
:rtype: float