Just imagine, how the processor would execute a typical spin-wait loop: 1 Spin_Lock: 2 CMP lockvar, 0 ; Check if lock is free 3 JE Get_Lock 4 JMP Spin_Lock 5 Get_Lock: After a few iterations the branch predictor will predict that the conditional branch (3) will never be taken and the pipeline will fill with … Read more
A stateless system can be seen as a box [black? ;)] where at any point in time the value of the output(s) depends only on the value of the input(s) [after a certain processing time] A stateful system instead can be seen as a box where at any point in time the value of the … Read more
Blocking communication is done using MPI_Send() and MPI_Recv(). These functions do not return (i.e., they block) until the communication is finished. Simplifying somewhat, this means that the buffer passed to MPI_Send() can be reused, either because MPI saved it somewhere, or because it has been received by the destination. Similarly, MPI_Recv() returns when the receive … Read more
The documentation says srun is used to submit a job for execution in real time while sbatch is used to submit a job script for later execution. They both accept practically the same set of parameters. The main difference is that srun is interactive and blocking (you get the result in your terminal and you … Read more
If your threads don’t do I/O, synchronization, etc., and there’s nothing else running, 1 thread per core will get you the best performance. However that very likely not the case. Adding more threads usually helps, but after some point, they cause some performance degradation. Not long ago, I was doing performance testing on a 2 … Read more