psis.py 文件源码

def sumlogs(x, axis=None, out=None):
    """Sum of vector where numbers are represented by their logarithms.

    Calculates np.log(np.sum(np.exp(x), axis=axis)) in such a fashion that it
    works even when elements have large magnitude.

    """
    maxx = x.max(axis=axis, keepdims=True)
    xnorm = x - maxx
    np.exp(xnorm, out=xnorm)
    out = np.sum(xnorm, axis=axis, out=out)
    if isinstance(out, np.ndarray):
        np.log(out, out=out)
    else:
        out = np.log(out)
    out += np.squeeze(maxx)
    return out