1,711 research outputs found
A Verified Certificate Checker for Finite-Precision Error Bounds in Coq and HOL4
Being able to soundly estimate roundoff errors of finite-precision
computations is important for many applications in embedded systems and
scientific computing. Due to the discrepancy between continuous reals and
discrete finite-precision values, automated static analysis tools are highly
valuable to estimate roundoff errors. The results, however, are only as correct
as the implementations of the static analysis tools. This paper presents a
formally verified and modular tool which fully automatically checks the
correctness of finite-precision roundoff error bounds encoded in a certificate.
We present implementations of certificate generation and checking for both Coq
and HOL4 and evaluate it on a number of examples from the literature. The
experiments use both in-logic evaluation of Coq and HOL4, and execution of
extracted code outside of the logics: we benchmark Coq extracted unverified
OCaml code and a CakeML-generated verified binary
Simple and Effective Type Check Removal through Lazy Basic Block Versioning
Dynamically typed programming languages such as JavaScript and Python defer
type checking to run time. In order to maximize performance, dynamic language
VM implementations must attempt to eliminate redundant dynamic type checks.
However, type inference analyses are often costly and involve tradeoffs between
compilation time and resulting precision. This has lead to the creation of
increasingly complex multi-tiered VM architectures.
This paper introduces lazy basic block versioning, a simple JIT compilation
technique which effectively removes redundant type checks from critical code
paths. This novel approach lazily generates type-specialized versions of basic
blocks on-the-fly while propagating context-dependent type information. This
does not require the use of costly program analyses, is not restricted by the
precision limitations of traditional type analyses and avoids the
implementation complexity of speculative optimization techniques.
We have implemented intraprocedural lazy basic block versioning in a
JavaScript JIT compiler. This approach is compared with a classical flow-based
type analysis. Lazy basic block versioning performs as well or better on all
benchmarks. On average, 71% of type tests are eliminated, yielding speedups of
up to 50%. We also show that our implementation generates more efficient
machine code than TraceMonkey, a tracing JIT compiler for JavaScript, on
several benchmarks. The combination of implementation simplicity, low
algorithmic complexity and good run time performance makes basic block
versioning attractive for baseline JIT compilers
Chaotic Compilation for Encrypted Computing: Obfuscation but Not in Name
An `obfuscation' for encrypted computing is quantified exactly here, leading
to an argument that security against polynomial-time attacks has been achieved
for user data via the deliberately `chaotic' compilation required for security
properties in that environment. Encrypted computing is the emerging science and
technology of processors that take encrypted inputs to encrypted outputs via
encrypted intermediate values (at nearly conventional speeds). The aim is to
make user data in general-purpose computing secure against the operator and
operating system as potential adversaries. A stumbling block has always been
that memory addresses are data and good encryption means the encrypted value
varies randomly, and that makes hitting any target in memory problematic
without address decryption, yet decryption anywhere on the memory path would
open up many easily exploitable vulnerabilities. This paper `solves (chaotic)
compilation' for processors without address decryption, covering all of ANSI C
while satisfying the required security properties and opening up the field for
the standard software tool-chain and infrastructure. That produces the argument
referred to above, which may also hold without encryption.Comment: 31 pages. Version update adds "Chaotic" in title and throughout
paper, and recasts abstract and Intro and other sections of the text for
better access by cryptologists. To the same end it introduces the polynomial
time defense argument explicitly in the final section, having now set that
denouement out in the abstract and intr
Cryptanalysis of a family of self-synchronizing chaotic stream ciphers
Unimodal maps have been broadly used as a base of new encryption strategies.
Recently, a stream cipher has been proposed in the literature, whose keystream
is basically a symbolic sequence of the (one-parameter) logistic map or of the
tent map. In the present work a thorough analysis of the keystream is made
which reveals the existence of some serious security problemsComment: 10 pages, 6 figure
An interface between single assignment C and vector Pascal
This dissertation contains an overview of the research I’ve been doing over in Glasgow University, which is mainly a project of developing an interface between two array programming languages, Single Assignment C and Vector Pascal, to combine them together by using the Vector Pascal code generator for Single Assignment C.
Single Assignment C provides support for multi-threading but it doesn’t contain any utilization of SIMD technology, and Vector Pascal implements array operations with the help of SIMD instruction sets of modern general processors. Thus my hypothesis is that this combination will let the program enjoy higher run-time performance compared to the one which is only compiled by using Single Assignment C’s compiler.
This dissertation explains the detail of designing and implementing this interface between these two languages; and the system to manipulate the three parts, i.e. the interface and the two languages’ compilers together to make them work automatically. The interface is generally developed based on traversal over Syntax Tree and involves works of vectorization and loop unrolling.
Meanwhile, a benchmark testing system to validate my hypothesis is created and introduced in this dissertation too, which is accompanied with the testing results and analysis
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