Speed-up happens before by using pandas logical operations.

    """

    check if a happens-before b in the trace

    """

    l = len(df[a])

    # check whether a and b occur in the same thread. If so, a and b cannot be

    # concurrent.

    ta = _get_thread_for_event(config, a)

    cname_a = str(a)[:-2] + "_C"

    cname_b = str(b)[:-2] + "_C"

    if (ta == tb and ta != None and tb != None):

        for i in range(l):

            tsa = df[a].iloc[i]

            tsb = df[b].iloc[i]

            if tsa > tsb:

        tg = df[a] > df[b]

        if tg.any():

            return False

            csa = df[cname_a].iloc[i]

            csb = df[cname_b].iloc[i]

            if tsa == tsb and csa > csb and csb != 0:

                return False

        return True

        df2 = df[df[a] == df[b]]

        return not ((df2[cname_a] > df2[cname_b]) & df2[cname_b] != 0).any()

    # since a and b occur in different threads, we cannot compare cyclestamps.

    # If in doubt, a and b are concurrent.

    for i in range(l):

        if df[a].iloc[i] >= df[b].iloc[i]:

            return False

    return True

    return not (df[a] >= df[b]).any()

def _fast_happens_before(df, a, b, hb):

    """