Blog 2: A continuation in the study of Anonymous Dynamic Distributed Computing without a Unique Leader

Since the last blog the progress that me and my professor have been making so far in strategizing ways of running our simulations in a faster way to collect as much data as possible.

Some of the methods we have discussed have mainly involved paralleling the section of code involved in matrix and vector multiplication in which an adjacency matrix is multiplied by a vector to give us our result in terms of rounds of phases for each node.

The work so far has been very intensive in not only understanding very deeply the Java library of multithreading but also the process of parallelism within a computer. How there is a significant difference between working with a sequential machine and a parallel machine and how the difference has a significant hinderance on the progress of the simulations. Because of that I have been studying very intensely fundamental operating systems concepts of context switching ,proper thread synchronization,  managing multiple processes within a single thread, fork-joins-pool methods etc.

This has lead to good personal experience by learning that theory and practice are two very different things. Theoretically with proper multithreading we were able to figure out that our work could be speed up from O(n^3)  computational time to O(lg(n)) computational time. To put that into perspective something something that takes 1000 days in O(n^3) could take only one day with O(lg(n)).That’s a difference of one day to nearly 3 years!However in practice by having more threads we are creating more work to be done with each thread with parallel programming and thus that could lead to the creation of more time if done recursively enough and especially if it exceeds the number of available cores we have which before used to be only 12 cores; no more than an average laptop!

For this reason we have been working intensely on speeding things up as much as possible in computational time and have been working with .slurm files so that we can tell that machine not only the files we want to run but also the commands and directives in terms of how long we want the simulations to run and how many tasks/CPU cores each task should run which I will add has been a very nice learning experience for myself running the batch commands on a very powerful school computer that is primarily done for research purposes.

Also I have learned to regularly meet with the professor as I do research and have first hand understood the dynamics of student-faculty research by communicating very clearly and promptly with my professor about issues or concerns with running the simulations or the amount of time that needs to be accounted for an all the meta-engineering tasks/problems that are involved with writing a theoretical paper.

For now we are both highly motivated to gather the data/run simulations and study it as much as possible now that we both know we currently have access to a  G.P.U machine with 3,840 cores available for our work we look forward for the work ahead and the research to come.


Blog 1: Polynomial Anonymous Dynamic Distributed Computing without a Unique Leader

The research between me and professor Miguel Mosteiro involves computing the number of nodes in an Anonymous Dynamic Network(A.D.N) without having just one unique leader. A anonymous Dynamic Network involves a network of nodes that do not have identifiers and where communication links between the nodes may change in arbitrarily and continuously over time.

Node anonymity in ADNs is motivated by expected applications of such communication infrastructure. For instance, in ad-hoc networks embedded in the Internet of Things, nodes may have to be deployed in a massive scale, and having unique identifiers may be impractical or inconvenient. Moreover, low node cost expectations may introduce uncertainty about the number of nodes that will effectively startup. Hence, the need of Counting.

The nodes in the network are divided into two categories of nodes. The network has a total of “n” nodes with a total of “l” black nodes that represent the nodes in the network that are known and a counted for. The other set of nodes are the white nodes for which their are “l -n” nodes. The nodes in the networks are to be run using two algorithms that are known as “Methodical Multi-Counting” or M.M.C and “Leaderless Methodical Multi-Counting” or L.M.M.C.The M.M.C algorithm uses a previously created Methodical Counting algorithm that was made in a previous paper by my professor but instead this algorithm is to implemented on multiple nodes in the network simultaneously while L.M.M.C uses the M.M.C algorithm as a subroutine while at the same time introducing an element of randomness as a Monte Carlo protocol.  These two methods are to be run in several hundred computer simulations to illustrate whether their is a change in the running time of Methodical counting when it is multi-leader and whether have a deterministic algorithm vs a non-deterministic algorithm could show any significant difference or improvement in running time.

So far our methods have been to code the many parallel threads for the L.M.M.C algorithm in which each black node to count the neighbors it’s attached to that are not counted for or aka white nodes in the network. Once all the nodes have been counted their are to be summed up once all threads are done computing. The code for M.M.C has been typed up pretty quickly and what’s left to do is to run simulations.

The simulations that will be run involve various types of graphs such as stars,trees,paths etc with varying sizes of n and varying sizes of black and white nodes. With running the two algorithms on varying types of graphs to demonstrate the impact of these algorithms and the subtlest changes that can be found when doing this research. We have come across the problem that even though we requested and received university computers that can run simulations with several multi-core processors which will help run the multiple threads in our network we still unfortunately keep seeing a sluggish and ungodly long amount of time for each individual simulation to be run. One simulation which had a network size of just 60 nodes took nearly 3 days for a deterministic algorithm to finish  and the simulations we are planning to run were ambitiously in the 100s.

As a result we are currently trying to devise ways in which we are to run not all the simulations in an incremental sense but types of comparable simulations that will allow the reader to still see the significance and impact of the work that was done. We are also noticing with the simulations that we run that their are local minima and maxima of optimization of counting these nodes such as the time for 20 nodes may be shorter than 10 let’s say. The work still continuing obviously and this possible relationship needs to be studied much more in depth. For now the work continues and hopefully will yield promising results for the time to come.