Message Passing Interface (MPI) is a standard library interface for writing parallel programs. The MPI specification is broadly used for solving engineering and scientific problems on parallel computers, and MPICH2 is a popular MPI implementation developed at Argonne National Laboratory. The scalability of MPI implementations is very important for building high performance parallel computing applications. The initial TCP (Transmission Control Protocol) network module developed for Nemesis communication sub-system in the MPICH2 library, however, was not scalable in how it established connections: pairwise connections between all of an application's processes were established during the initialization of the application (the library call to MPI_Init), regardless of whether the connections were eventually needed or not. In this work, we have developed a new TCP network module for Nemesis that establishes connections on-demand. The on-demand connection establishment scheme is designed to improve the scalability of the TCP network module in MPICH2 library, aiming to reduce the initialization time and the use of operating system resources of MPI applications. Our performance benchmark results show that MPI_Init in the on-demand connection establishment scheme becomes a fast constant time operation, and the additional cost of establishing connections later is negligible. The on-demand connection establishment between two processes, especially when two processes attempt to connect to each other simultaneously, is a complex task due to race-conditions and thus prone to hard-to-reproduce defects. To assure ourselves of the correctness of the TCP network module, we modeled its design using the SPIN model checker, and verified safety and liveness properties stated as Linear Temporal Logic claims.

In view of Bluetooth?s growing popularity a lot of research is being done to improve the performance of Bluetooth. Most of the research being performed prerequisites that a connection has already been made. Due to the frequency hopping spread spectrum used by Bluetooth the connection establishment is not as easy as it seams. Two processes have been derived to bridge the frequency discrepancies between devices, inquiry and page. In this thesis, we study the inquiry and page processes and the time it takes to complete a connection with no, one or two voice channels present at the initiating device. We have found the times to complete the processes to be lengthy at best, unreasonably long if there is voice traffic present. Through optimisation, we have decreased the mean time to connect. We propose some changes to the default values of a few time outs and variables, which yields a substantial improvement in performance, especially in the case when there is voice traffic present. The changes are in the software only, no changes in hardware are necessary. After a connection is made a client may want to start using the services of the device it is connected to. This is another topic of this thesis. Bluetooth does not provide means of accessing a service, only discovering it. Thus, there is the need for higher-level protocols for accessing services. We have investigated some of the service discovery protocols currently available. / Med tanke på Bluetooth-teknikens växande popularitet bedrivs mycket forskning för att förbättra Bluetooth-teknikens prestanda. Den mesta delen av forskningen förutsätter att en uppkoppling redan skett. På grund av frekvenshoppningstekniken som används i Bluetooth är detta inte så lätt som det låter. För att överkomma frekvensskillnaden mellan enheter används två processer, inquiry och page. I denna uppsats studerar vi inquiry- och page-processerna och studerar tiden det tar att slutföra en uppkoppling med ingen, en eller två tal-kanaler redan uppkopplade. Vi har funnit att tiden det tar är i bästa fall lång, om det finns tal-kanaler uppkopplade är tidsåtgången oacceptabel. Genom optimering av en del variabler och time-outs har vi lyckats reducera uppkopplingstiden, speciellt i fallet med tal-kanaler redan uppkopplade. Våra föreslagna ändringar är endast i mjukvaran, inga hårdvaruändringar är nödvändiga. Efter att uppkopplingen är slutförd kommer användaren att vilja börja använda de tjänster som erbjuds. Detta är en annan del av uppsatsen. Bluetooth-tekniken tillhandahåller inte något sätt att tillgodogöra sig tjänster, bara att upptäcka dem. Därför behövs det protokoll för att lösa detta. Vi har undersökt en del av de så kallade "service discovery"-protokoll som finns tillgängliga idag