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Théophile Bastian 2017-08-24 15:10:07 +02:00
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@ -98,3 +98,10 @@
publisher={IEEE}
}
@misc{sysdig_cpu,
author={Théophile Bastian and Noémie Cartier and Nathanaël Courant},
title={``Système digital'' project},
howpublished={\url{https://github.com/tobast/sysdig-full/}},
year=2016
}

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\usepackage{enumerate}
\usepackage{caption}
\usepackage{algorithmicx}
%\usepgfplotslibrary{external}
%\tikzexternalize
\usepackage[backend=biber,style=trad-alpha]{biblatex}
\usepackage[left=2cm,right=2cm,top=2cm,bottom=2cm]{geometry}
@ -21,6 +24,8 @@
\usepackage{../common/internship}
\usepackage{../common/math}
\usepackage{pgfplots}
\bibliography{../common/refs}
\title{Pattern-matching and substitution in electronic circuits}
@ -574,7 +579,84 @@ many times in the haystack. This simple check saved a lot of time.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Performance}
\todo{}
In this section, all the measures were made on a computer with an Intel
i7-3770 CPU (3.40GHz) and 8\,GB of RAM\@. % chktex 8
\subsection{Small processor}
The example I used widely during my project to test my program and check its
efficiency periodically was a small processor designed one year earlier as a
school project~\cite{sysdig_cpu}. The processor implements a large subset of
ARM, was conceived as a few hierarchized modules (ALU, registers, opcode
decoder, \ldots) but was flattened as a plain netlist when generated from its
python code, so I first had to patch its generator code to make its hierarchy
apparent.
The processor, in the end, has around 2000 leaf gates (but works at word level)
and 240 hierarchy groups. \qtodo{Tell us more!}
\paragraph{Signature.} First, the time required to sign the whole circuit with
different levels of signature (\ie{} the order of signature computed for every
part of the circuit). In practice, we never compute high order signatures for a
whole circuit, as signature of subgroups are always computed by default at the
order $2$, unless this particular group needs a more accurate signature.
The measures were made for 100 consecutive runs of the program (then averaged
for a single run) and measured by the command \texttt{time}.
\begin{center}
\begin{tikzpicture}
\begin{axis}[
title={Signature time of the processor for different levels
of signature},
xlabel={Level of signature},
ylabel={Time (ms)},
xmin=0, xmax=16,
ymin=0, ymax=300,
legend pos=north west,
ymajorgrids=true,
grid style=dashed,
]
\addplot[
color=blue,
mark=square,
]
coordinates {
(2,105.4)
(3,122.6)
(4,140.1)
(5,155.4)
(6,171.2)
(7,183.9)
(8,198.3)
(9,211.2)
(10,224.3)
(11,236.7)
(12,248.5)
(13,259.3)
(14,271.7)
(15,281.4)
};
\legend{-O3}
\end{axis}
\end{tikzpicture}
\end{center}
\paragraph{Equality.} To test the circuit group equality, a small piece of
code takes a circuit, scrambles it as much as possible
--- without altering its structure ---, \eg{} by renaming randomly its parts,
by randomly changing the order of the circuits and groups, \ldots The circuit
is then matched with its unaltered counterpart.
For the processor described above, it takes about \textbf{477\,ms} to
prove it equal to its scrambled version, and then the other way around. Yet,
the memoized results (essentially the signatures) are kept for the second one,
considerably speeding it up: the same program proving only one way takes about
\textbf{475\,ms}. \todo{explain why}
\subsection{Corner cases}