void PushInvList(int index)
{
var ilist = this.invindex[index];
var ipos = pos[index];
if (ipos < ilist.Count) {
// Console.WriteLine ("n: {0}, ipos: {1}", ilist.Count, ipos);
int key = ilist[ipos] >> this.lsd_block;
this.pqueue_array[key].Push (index);
}
}