'uses exact solution for log of process'

def exactprocess(self, xzero, nobs, ddt=1.0, nrepl=2):

    lnxzero = np.log(xzero)
    lnx = super(self.__class__, self).exactprocess(xzero, nobs, ddt=ddt, nrepl=nrepl)
    return np.exp(lnx)
