733 research outputs found

    GPUVerify: A Verifier for GPU Kernels

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    We present a technique for verifying race- and divergence-freedom of GPU kernels that are written in mainstream ker-nel programming languages such as OpenCL and CUDA. Our approach is founded on a novel formal operational se-mantics for GPU programming termed synchronous, delayed visibility (SDV) semantics. The SDV semantics provides a precise definition of barrier divergence in GPU kernels and allows kernel verification to be reduced to analysis of a sequential program, thereby completely avoiding the need to reason about thread interleavings, and allowing existing modular techniques for program verification to be leveraged. We describe an efficient encoding for data race detection and propose a method for automatically inferring loop invari-ants required for verification. We have implemented these techniques as a practical verification tool, GPUVerify, which can be applied directly to OpenCL and CUDA source code. We evaluate GPUVerify with respect to a set of 163 kernels drawn from public and commercial sources. Our evaluation demonstrates that GPUVerify is capable of efficient, auto-matic verification of a large number of real-world kernels

    Symbolic crosschecking of data-parallel floating-point code

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    Engineering a static verification tool for GPU kernels

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    We report on practical experiences over the last 2.5 years related to the engineering of GPUVerify, a static verification tool for OpenCL and CUDA GPU kernels, plotting the progress of GPUVerify from a prototype to a fully functional and relatively efficient analysis tool. Our hope is that this experience report will serve the verification community by helping to inform future tooling efforts. © 2014 Springer International Publishing

    Doctor of Philosophy

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    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

    Fast and Precise Symbolic Analysis of Concurrency Bugs in Device Drivers

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    © 2015 IEEE.Concurrency errors, such as data races, make device drivers notoriously hard to develop and debug without automated tool support. We present Whoop, a new automated approach that statically analyzes drivers for data races. Whoop is empowered by symbolic pairwise lockset analysis, a novel analysis that can soundly detect all potential races in a driver. Our analysis avoids reasoning about thread interleavings and thus scales well. Exploiting the race-freedom guarantees provided by Whoop, we achieve a sound partial-order reduction that significantly accelerates Corral, an industrial-strength bug-finder for concurrent programs. Using the combination of Whoop and Corral, we analyzed 16 drivers from the Linux 4.0 kernel, achieving 1.5 - 20× speedups over standalone Corral

    The design and implementation of a verification technique for GPU Kernels

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    We present a technique for the formal verification of GPU kernels, addressing two classes of correctness properties: data races and barrier divergence. Our approach is founded on a novel formal operational semantics for GPU kernels termed synchronous, delayed visibility (SDV) semantics, which captures the execution of a GPU kernel by multiple groups of threads. The SDV semantics provides operational definitions for barrier divergence and for both inter- and intra-group data races. We build on the semantics to develop a method for reducing the task of verifying a massively parallel GPU kernel to that of verifying a sequential program. This completely avoids the need to reason about thread interleavings, and allows existing techniques for sequential program verification to be leveraged. We describe an efficient encoding of data race detection and propose a method for automatically inferring the loop invariants that are required for verification. We have implemented these techniques as a practical verification tool, GPUVerify, that can be applied directly to OpenCL and CUDA source code. We evaluate GPUVerify with respect to a set of 162 kernels drawn from public and commercial sources. Our evaluation demonstrates that GPUVerify is capable of efficient, automatic verification of a large number of real-world kernels

    Scalable SMT-based verification of GPU kernel functions

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