Doctor of Philosophy

dissertationGraphics processing units (GPUs) are highly parallel processors that are now commonly used in the acceleration of a wide range of computationally intensive tasks. GPU programs often suffer from data races and deadlocks, necessitating systematic testing. Conventional GPU debuggers are ineffective at finding and root-causing races since they detect errors with respect to the specific platform and inputs as well as thread schedules. The recent formal and semiformal analysis based tools have improved the situation much, but they still have some problems. Our research goal is to aply scalable formal analysis to refrain from platform constraints and exploit all relevant inputs and thread schedules for GPU programs. To achieve this objective, we create a novel symbolic analysis, test and test case generator tailored for C++ GPU programs, the entire framework consisting of three stages: GKLEE, GKLEEp, and SESA. Moreover, my thesis not only presents that our framework is capable of uncovering many concurrency errors effectively in real-world CUDA programs such as latest CUDA SDK kernels, Parboil and LoneStarGPU benchmarks, but also demonstrates a high degree of test automation is achievable in the space of GPU programs through SMT-based symbolic execution, picking representative executions through thread abstraction, and combined static and dynamic analysis

Parameterized Verification of GPU Kernel Programs

Abstract—We present an automated symbolic verifier for checking the functional correctness of GPGPU kernels parametrically, for an arbitrary number of threads. Our tool PUGpara checks the functional equivalence of a kernel and its optimized versions, helping debug errors introduced during memory coalescing and bank conflict elimination related optimizations. Key features of our work include: (1) a symbolic method to encode a comparative assertion across two kernel versions, and (2) techniques to overcome SMT solver restrictions through overapproximations, yielding an efficient bug-hunting method