5,119 research outputs found
Modeling and visualizing networked multi-core embedded software energy consumption
In this report we present a network-level multi-core energy model and a
software development process workflow that allows software developers to
estimate the energy consumption of multi-core embedded programs. This work
focuses on a high performance, cache-less and timing predictable embedded
processor architecture, XS1. Prior modelling work is improved to increase
accuracy, then extended to be parametric with respect to voltage and frequency
scaling (VFS) and then integrated into a larger scale model of a network of
interconnected cores. The modelling is supported by enhancements to an open
source instruction set simulator to provide the first network timing aware
simulations of the target architecture. Simulation based modelling techniques
are combined with methods of results presentation to demonstrate how such work
can be integrated into a software developer's workflow, enabling the developer
to make informed, energy aware coding decisions. A set of single-,
multi-threaded and multi-core benchmarks are used to exercise and evaluate the
models and provide use case examples for how results can be presented and
interpreted. The models all yield accuracy within an average +/-5 % error
margin
Static analysis of energy consumption for LLVM IR programs
Energy models can be constructed by characterizing the energy consumed by
executing each instruction in a processor's instruction set. This can be used
to determine how much energy is required to execute a sequence of assembly
instructions, without the need to instrument or measure hardware.
However, statically analyzing low-level program structures is hard, and the
gap between the high-level program structure and the low-level energy models
needs to be bridged. We have developed techniques for performing a static
analysis on the intermediate compiler representations of a program.
Specifically, we target LLVM IR, a representation used by modern compilers,
including Clang. Using these techniques we can automatically infer an estimate
of the energy consumed when running a function under different platforms, using
different compilers.
One of the challenges in doing so is that of determining an energy cost of
executing LLVM IR program segments, for which we have developed two different
approaches. When this information is used in conjunction with our analysis, we
are able to infer energy formulae that characterize the energy consumption for
a particular program. This approach can be applied to any languages targeting
the LLVM toolchain, including C and XC or architectures such as ARM Cortex-M or
XMOS xCORE, with a focus towards embedded platforms. Our techniques are
validated on these platforms by comparing the static analysis results to the
physical measurements taken from the hardware. Static energy consumption
estimation enables energy-aware software development, without requiring
hardware knowledge
Producing Scheduling that Causes Concurrent Programs to Fail
A noise maker is a tool that seeds a concurrent program with conditional synchronization primitives (such as yield()) for the purpose of increasing the likelihood that a bug manifest itself. This work explores the theory and practice of choosing where in the program to induce such thread switches at runtime. We introduce a novel fault model that classifies locations as .good., .neutral., or .bad,. based on the effect of a thread switch at the location. Using the model we explore the terms in which efficient search for real-life concurrent bugs can be carried out. We accordingly justify the use of probabilistic algorithms for this search and gain a deeper insight of the work done so far on noise-making. We validate our approach by experimenting with a set of programs taken from publicly available multi-threaded benchmark. Our empirical evidence demonstrates that real-life behavior is similar to what our model predicts
Computing for Perturbative QCD - A Snowmass White Paper
We present a study on high-performance computing and large-scale distributed
computing for perturbative QCD calculations.Comment: 21 pages, 5 table
Symbolic Partial-Order Execution for Testing Multi-Threaded Programs
We describe a technique for systematic testing of multi-threaded programs. We
combine Quasi-Optimal Partial-Order Reduction, a state-of-the-art technique
that tackles path explosion due to interleaving non-determinism, with symbolic
execution to handle data non-determinism. Our technique iteratively and
exhaustively finds all executions of the program. It represents program
executions using partial orders and finds the next execution using an
underlying unfolding semantics. We avoid the exploration of redundant program
traces using cutoff events. We implemented our technique as an extension of
KLEE and evaluated it on a set of large multi-threaded C programs. Our
experiments found several previously undiscovered bugs and undefined behaviors
in memcached and GNU sort, showing that the new method is capable of finding
bugs in industrial-size benchmarks.Comment: Extended version of a paper presented at CAV'2
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