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Small backports from paper

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Théophile Bastian 2024-06-20 17:56:52 +02:00
parent 59de13b1d1
commit ef62c3b7e5
2 changed files with 17 additions and 21 deletions
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2
manuscrit/60_staticdeps/35_rob_proof.tex
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@ -59,7 +59,7 @@ $(i_q)_{q\in Q_p}$ are the \uops{} obtained from the decoding of $I_p$.
\begin{lemma}[Distance of in-flight \uops{}]
For any pair of instructions $(I_p,I_{p'})$, and two corresponding \uops{},
$(i_q,i_{q'})$ such that q \in Q_p, q' \in Q_{p'}$,
$(i_q,i_{q'})$ such that $q \in Q_p, q' \in Q_{p'}$,
\[
\operatorname{inflight}(i_q) \wedge \operatorname{inflight}(i_{q'}) \Rightarrow \distance{I_p}{I_{p'}}<R
\]

36
manuscrit/60_staticdeps/50_eval.tex
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@ -28,7 +28,6 @@ benchmarks, making the analysis more convenient.
In practice, benchmarks from \cesasme{} are roughly of the following form:
\begin{lstlisting}[language=C]
/* Initialize A, B, C here */
for(int measure=0; measure < NUM_MEASURES; ++measure) {
measure_start();
for(int repeat=0; repeat < NUM_REPEATS; ++repeat) {
@ -41,7 +40,7 @@ for(int measure=0; measure < NUM_MEASURES; ++measure) {
\end{lstlisting}
While this is sensible for conducting throughput measures, it also introduces
unwanted dependencies \todo{explain why}. If, for instance, the kernel consists in
unwanted dependencies. If, for instance, the kernel consists in
$A[i] = C\times{}A[i] + B[i]$, implemented by\\
\begin{minipage}{0.95\linewidth}
\begin{lstlisting}[language={[x86masm]Assembler}]
@ -100,8 +99,9 @@ source and destination program counters are not in the same basic block are
discarded, as \staticdeps{} cannot detect them by construction.
For each of the considered basic blocks, we run our static analysis,
\staticdeps{}. We discard the $\Delta{}k$ parameter, as our dynamic analysis does
not report an equivalent parameter, but only a pair of program counters.
\staticdeps{}. We discard the $\Delta{}k$ parameter --~how many loop iterations
the dependency spans~--, as our dynamic analysis does not report an equivalent
parameter, but only a pair of program counters.
Dynamic dependencies from \depsim{} are converted to
\emph{periodic dependencies} in the sense of \staticdeps{} as described in
@ -281,25 +281,21 @@ the corresponding box-plots in \autoref{fig:staticdeps_uica_cesasme_boxplot}.
\medskip{}
The full dataset \uicadeps{} row is extremely close, on every metric, to the
pruned, \uica{}-only row. On this basis, we argue that \staticdeps{}' addition
to \uica{} is very conclusive: the hints provided by \staticdeps{} are
We deduce two things from this experiment.
First, the full dataset \uicadeps{} row is extremely close, on every metric, to
the pruned, \uica{}-only row. On this basis, we argue that \staticdeps{}'
addition to \uica{} is very conclusive: the hints provided by \staticdeps{} are
sufficient to make \uica{}'s results as good on the full dataset as they were
before on a dataset pruned of precisely the kind of dependencies we aim to
detect. Furthermore, \uica{} and \uicadeps{}' results on the pruned dataset are
extremely close: this further supports the accuracy of \staticdeps{}.
detect. Thus, at least on workloads similar to Polybench, \staticdeps{} is able
to resolve the issue of memory-carried dependencies for \uica{}'s throughput
analysis.
\medskip{}
While the results obtained against \depsim{} in
\autoref{ssec:staticdeps_eval_depsim} above were reasonable, they were not
excellent either, and showed that many kind of dependencies were still missed
by \staticdeps{}. However, our evaluation on \cesasme{} by enriching \uica{}
shows that, at least on the workload considered, the dependencies that actually
matter from a performance debugging point of view are properly found.
This, however, might not be true for other kinds of applications that would
require a dependencies analysis.
Furthermore, \uica{} and \uicadeps{}' results on the pruned dataset are
extremely close. From this, we argue that \staticdeps{} does not introduce
false positives when no dependency should be found; its addition to \uica{}
does not negatively impact its accuracy whenever it is not relevant.
\subsection{Analysis speed}