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Krzysztof kuhy Rudnicki
ffa5dad02a
The 250-line cap applies to prose too, and the reports were the worst
offenders -- ENUME's projectA.tex alone was 1,876 lines. Each is now a
preamble plus one \input{} per section, which is how a long LaTeX document is
normally organised; not one byte of prose was rewritten.
"The PDF is unchanged" is checked by a script rather than by eye, because
hashing the PDF cannot work: pdflatex stamps a /CreationDate and an /ID into
every build, so two runs of the SAME source already differ. tex_fingerprint.sh
compares what a reader sees instead -- page count plus a hash of the extracted
text -- and it is stable across rebuilds of untouched sources, which is the
property that makes it usable as a gate.
It earned its keep immediately. Both ECOTE reports quote an example LaTeX
document inside an lstlisting block, so \end{document} appears in the middle
of the file; splitting on the FIRST one stranded everything after it. Same
page count, different text, caught automatically. EOPSY lab3 exposed a second
bug: a \section{} title that runs onto the next line.
Result: 19 .tex over the cap -> 1. The survivor,
ELAC/.../03-building-nfa-...tex, is 418 lines of consecutive tikz figures
with no subsection to split on and needs a hand-placed boundary.
Verified: 29 splits across two passes (section, then subsection for the
pieces still over), every one reporting `unchanged` from
scripts/tex_fingerprint.sh --check.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0172dj34FDpao6wsix8ZuCzE
61 lines
2.8 KiB
TeX
61 lines
2.8 KiB
TeX
\section{Introduction}
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\subsection{Page replacement algorithms}
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\paragraph{First in First out}
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What page replacament algorithm is being used? \\
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We use FIFO (First in First out) page replacement algorithm for those laboratories as indicated
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by the PageFault.java file line 18
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\begin{figure}[H]
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\caption{PageFault.java file}
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\begin{lstlisting}[language=Java]
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[...]
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public class PageFault {
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/**
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* The page replacement algorithm for the memory management sumulator.
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* This method gets called whenever a page needs to be replaced.
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* <p>
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* The page replacement algorithm included with the simulator is
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* FIFO (first-in first-out). A while or for loop should be used
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* to search through the current memory contents for a canidate
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* replacement page. In the case of FIFO the while loop is used
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* to find the proper page while making sure that virtPageNum is
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* not exceeded.
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[...]
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\end{lstlisting}
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\end{figure}
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All pages are stored in memory in a queue. Oldest page (First that came in) is
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in front of this queue. \\ When we need to replace the page we remove the page that
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is first in queue (so the one that came in as a first one, first in, first out)
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\\
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It is easy to explain and implement but in practical application it performs
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poorly. It is still used but usually we use modified version of it.
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\cite{Page Replacement Algorithms}
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\paragraph{Optimal Page Replacement}
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We replace pages which in the future will not be used for the longest time.
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This is purely theoretical algorithm. It is perfect but not doable in practice
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since operating systems can not know future requests. \\
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It is used as a benchmark against which we compare other algorithms.
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\cite{Page Replacement Algorithms}
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\paragraph{Least Recently Used}
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We replace page which was not used for the longest time. \\
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It is based on the idea that we will in future work on pages which we used
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heavily in the past. In theory its performance can be close to optimal one but
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in practice it is expensive to implement. \\
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Most expensive way of implementing this algorithm is using linked lists. Most
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recently used pages in front, least recently used in the back. Every time we
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reference memory we have to move elements in list which takes a lot of time. \\
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We can also use operating system counter \\
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This algorithm is often used in different cheaper modified versions.
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\cite{Page Replacement Algorithms}
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\cite{pageWiki}
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\subsection{Other}
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\paragraph{Memory Management Unit}
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Hardware unit which translates virtual memory to physical one.
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\cite{mmuWiki}
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\paragraph{Page fault}
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Exception raised when process wants to access page without preparations.
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Preparation consists of adding the mapping to process's virtual address space
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and/or loading page from a disk. MMU detects the fault but it is up to kernel
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and/or loading page from a disk.
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