Parameters
        ----------
        valid : 1D bool array
            Validity mask.

        Returns
        -------
        int array
            Array so that (`valid_array` being a compressed array
            based on a `masked_array` with mask ~*valid*):

            - For all i with valid[i] = True:
              valid_array[renum[i]] = masked_array[i]
            - For all i with valid[i] = False:
              renum[i] = -1 (invalid value)
        r+