po.noneq[i1] = bs
	} else if bs.Test(i2) {
		// Already recorded
		return
	}
	bs.Set(i2)
	po.upushneq(i1, i2)
}

// CheckIntegrity verifies internal integrity of a poset. It is intended
// for debugging purposes.
func (po *poset) CheckIntegrity() {
	// Record which index is a constant
	constants := newBitset(int(po.lastidx + 1))
	for _, c := range po.constants {
		constants.Set(c)
	}