Hello,
I am sorry for the delayed reply, this email got lost during the
Finals week :-)
If you need help on how to make use of MPI_Test and MPI_Wait to complete
the non-blocking send and receive operations, please see:
http://www.cz3.nus.edu.sg/~yzchen/teach/cz3201/mpi4.html
Another good tutorial can be found at:
http://webct.ncsa.uiuc.edu:8900/public/MPI/
Hope this helps.
Prashanth Charapalli,
LAM/MPI Team.
->Date: Mon, 15 Dec 2003 15:19:42 +0700
->From: Arie Hintono <arie_h_at_[hidden]>
->Reply-To: General LAM/MPI mailing list <lam_at_[hidden]>
->To: lam_at_[hidden]
->Subject: LAM: Asking about the implementing branch and bound algorithm in
-> parallel
->
->I want to implement branch and bound algorithm in parallel, the
->illustration is like this:
->There are n processors, and a binary search tree. First, there is only one
->node in tree, and it is processed by the first processor, and then if
->branching, there will be two node in tree, the first one will proccessed by
->the same processor and the second one will be sent to the one of available
->processor, if there is no available processor then it will processed in the
->same processor, and so on.
->
->Also there are variable Z_optimal and Z_current, where Z_optimal is the
->lower bound of best solution and Z_current is the value of the current
->solution, and if one processor found new Z_Optimal, it should broadcast it
->to all processors.
->
->How can I check the status of all processor whether it's available or not
->depending on the number of the tree nodes they currently have, if the
->number of the node is 0 then it's available else it's not available. If the
->processor is available then one of the processor that have more than 1 node
->send 1 node to that processor. And the computation end if all processor are
->available (there is no active node in tree).
->
->What I think is: there is an array variable that keep the status of all
->processor and if one processor change it's status locally then it's should
->broadcast to all other processor.
->
->The algorithm is like this:
->
->Set proc_status[0]=1 and the other is set 0; // 0 = proc is available and 1
->= proc is not available
->while (not all proc available) {
-> if (numnode == 0) {
-> //Wait from other proc to send node;
-> if (receiving node) then set proc_status[my_rank]=1 and broadcast the
->proc_status;
-> }
-> else {
-> if (numnode > 1 and there is proc available) then send 1 node to the
->available proc;
-> doing computation;
-> if (Z_current >= Z_optimal) then prune the node;
-> else { // Z_current < Z_optimal
-> if (solution not integer) then branching;
-> else set Z_optimal=Z_current and broadcast Z_Optimal;
-> }
-> }
->}
->
->I have already try to use MPI_Bcast, it's not work because inside the loop,
->other processor didn't access it
->And also if I use the MPI_Send and MPI_Recv, but if there is no data send,
->than MPI_Recv will always waiting, and I want my program continue to work
->and not waiting if there is no updating data.
->I also try the MPI_Irecv and MPI_Test but I still confused how they work
->because when I use them sometime some processor receive it but more often
->no processors receive the value that already send by one processor. How to
->make sure that the data is received by processor and not lost ?
->
->How to implement the correct and efficient brodcast of proc_status and the
->Z_Optimal also the sending and receiving the node or is there better
->solution to my program?
->
->Thank you, and sorry if my English is bad and my question is too long.
->
->
->_______________________________________________
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->
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