Sarvani S. Vakkalanka

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A significant body of parallel programs are written using MPI [1]. Bugs in MPI programs arise due to many reasons, for example: (i) during manual optimizations that turn blocking sends/receives into their non-blocking counterparts, (ii) in the context of using wild-card communications (and the resulting non-determinism), and (iii) in programs that use(More)
This paper considers the problem of formal verification of MPI programs operating under a fixed test harness for safety properties without building verification models. In our approach, we directly model-check the MPI/C source code, executing its interleavings with the help of a verification scheduler. Unfortunately, the total feasible number of(More)
Dynamic verification methods are the natural choice for debugging real world programs when model extraction and maintenance are expensive. Message passing programs written using the MPI library fall under this category. Partial order reduction can be very effective for MPI programs because for each process, all its local computational steps, as well as many(More)
We examine the problem of formally verifying MPI programs for safety properties through an efficient dynamic (runtime) method in which the processes of a given MPI program are executed under the control of an interleaving scheduler. To ensure full coverage for given input test data, the algorithm must take into consideration MPI’s out-of-order completion(More)
Dynamic verification methods are the natural choice for formally verifying real world programs when model extraction and maintenance are expensive. Message passing programs written using the MPI library often fall under this category, especially when these programs have to be verified after being ported to new platforms and iteratively optimized. However,(More)
There is growing need to develop formal verification tools for Message Passing Interface (MPI) programs to eliminate bugs such as deadlocks and local assertion violations. Of all approaches, dynamic verification is most practical for MPI. Since the number of interleavings of concurrent programs grow exponentially, we devise a dynamic interleaving reduction(More)
We examine the unsolved problem of automatically and efficiently detecting functionally irrelevant barriers in MPI programs. A functionally irrelevant barrier is a set of MPI_Barrier calls, one per MPI process, such that their removal does not alter the overall MPI communication structure of the program. Static analysis methods are incapable of solving this(More)
Increasing the amount of buffering for MPI sends is an effective way to improve the performance of MPI programs. However, for programs containing non-deterministic operations, this can result in new deadlocks or other safety assertion violations. Previous work did not provide any characterization of the space of slack elastic programs: those for which(More)
We consider the problem of verifying MPI programs that use MPI_Probe and MPI_Iprobe. Conventional testing tools, known to be inadequate in general, are even more so for testing MPI programs containing MPI probes. A few reasons are: (i) use of the MPI_ANY_SOURCE argument can make MPI probes non-deterministic, allowing them to match multiple senders, (ii) an(More)
Overview: It is well known that the number of schedules (interleavings) of a concurrent program grows exponentially with the number of processes. Our previous work has demonstrated the advantages of an MPI-specific dynamic partial order reduction (DPOR, [5]) algorithm called POE in a tool called ISP [1,2,3] in dramatically reducing the number of(More)