initial lots done

lots can run 1000 nodes splitting/merging now,
next step is to realize b/v

add lm_align_pos

when pos is not aligned to zero, it will goes exponentially, and easily fall into the minus axis, leading to bugs.

bugs

1. mergeSet is changed by peers, stockMergeSet is used to reserve

GNP: Global Network Positioning

http://www.cs.cmu.edu/~eugeneng/research/gnp/

To bridge the gap between the contradicting goals of performance optimization and scalability, we believe a promising approach is to attempt to predict the network distance (i.e., round-trip propagation and transmission delay, a relatively stable characteristic) between hosts, and use this as a first-order discriminating metric to greatly reduce or eliminate the need for on-demand network measurements. Therefore, the critical problem is to devise techniques that can predict network distance accurately, scalably, and in a timely fashion.

Global Network Positioning (GNP) is a solution designed to achieve these goals. The key idea is to represent the complex structure of the Internet by a simple geometric space (e.g. an N-dimensional Euclidean space). In this representation, each host in the Internet is characterized by its position in the geometric space with a set of geometric coordinates. If the representation is accurate, then the easily computable geometric distances between hosts in this geometric space can accurately approximate the Internet network distances, and no actual network measurements are required. In extensive Internet experiments, we have found that by using a 7-dimensional Euclidean space, in 90% of the cases, GNP can predict the Internet distances among a globally distributed set of hosts with less than 50% error. The accuracy is even higher when the hosts are restricted to within a single Autonomous System.

excerpt from http://en.wikipedia.org/wiki/Anycast

Anycast is a network addressing and routing scheme whereby data is routed to the "nearest" or "best" destination as viewed by the routing topology.

The term is intended to echo the terms unicast, broadcast and multicast.

• In unicast, there is a one-to-one association between network address and network endpoint: each destination address uniquely identifies a single receiver endpoint.
• In broadcast and multicast, there is a one-to-many association between network addresses and network endpoints: each destination address identifies a set of receiver endpoints, to which all information is replicated.
• In anycast, there is also a one-to-many association between network addresses and network endpoints: each destination address identifies a set of receiver endpoints, but only one of them is chosen at any given time to receive information from any given sender.

related conferences:
sigmod, icde, vldb, sigcomm, hotnets, iptps, dbisp2p, webdb

reader/writer

from http://cne.gmu.edu/modules/ipc/orange/readmon.html

  monitor ReadersWriters
   condition OKtoWrite, OKtoRead; 
   int ReaderCount = 0;
   Boolean busy = false;
  

 procedure StartRead()
 {
   if (busy)   // if database is not free, block
     OKtoRead.wait;
   ReaderCount++;                      // increment reader ReaderCount
   OKtoRead.signal();

 }

 procedure EndRead()
 {
    ReaderCount-- ;   // decrement reader ReaderCount
    if ( ReaderCount == 0 )
       OKtoWrite.signal();
 }


 procedure StartWrite()
 {
   if ( busy || ReaderCount != 0 )
      OKtoWrite.wait();
   busy = true;
 }

 procedure EndWrite()
 {
   busy = false;
   If (OKtoRead.Queue)
     OKtoRead.signal();
   else
     OKtoWrite.signal();
  }

 Reader()
 {
    while (TRUE)  // loop forever     
    {
       ReadersWriters.StartRead();
  readDatabase();   // call readDatabase function in monitor
       ReadersWriters.EndRead();
    }
 }

 Writer()
 {
    while (TRUE)  // loop forever
    {
 make_data(&info);  // create data to write
       ReaderWriters.StartWrite();
 writeDatabase();  // call writeDatabase function in monitor
       ReadersWriters.EndWrite();
    }
 }