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<HTML><HEAD><TITLE>Projects</TITLE></HEAD><BODY bgcolor="#FFFFFF"> <a href="../index.html" target="_top"><img src="../icons/usins.gif" alt="Logo" align=right></a><b>Data Structures and Algorithms with Object-Oriented Design Patterns in Python</b><br><A NAME="tex2html6143" HREF="page433.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="../icons/next_motif.gif"></A> <A NAME="tex2html6141" HREF="page415.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="../icons/up_motif.gif"></A> <A NAME="tex2html6137" HREF="page431.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="../icons/previous_motif.gif"></A> <A NAME="tex2html6145" HREF="page611.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="../icons/index_motif.gif"></A> <BR><HR><H1><A NAME="SECTION0013700000000000000000">Projects</A></H1><P><OL><LI> Devise and conduct a set of experiments to measure garbage collection overhead. For example, write a program that creates a specified number of garbage objects as quickly as possible. Determine the number of objects needed to trigger garbage collection. Measure the running time of your program when no garbage collection is performed and compare it to the running time observed when garbage collection is invoked.<LI> Python does not provide the means for accessing memory directly. Consequently, it is not possible to implement the Python heap in Python (without using native methods). Nevertheless, we can <em>simulate</em> a heap using a Python array of <tt>int</tt>s. Write a Python class that manages an array of <tt>int</tt>s. Your class should implement the following methods:<PRE>class Heap(object): def acquire(self, size): "(Heap, int) -> int" # ... def release(self, offset): "(Heap, int) -> None" # ... def __getitem__(self, offset): "(Heap, int) -> int" # ... def __setitem__(self, offset, value): "(Heap, int, int) -> None" # ...</PRE> The <tt>acquire</tt> method allocates a region of <tt>size</tt> consecutive <tt>int</tt>s in the array and returns the offset of the first <tt>int</tt> in the region. The <tt>release</tt> method release a region of <tt>int</tt>s at the specified offset which was obtained previously using <tt>acquire</tt>. The <tt>__getitem__</tt> and <tt>__setitem__</tt> methods access a value in the array at a given offset.<LI><A NAME="projectgarbageproject3"> </A> Using an array of <tt>int</tt>s simulate the <em>mark-and-sweep</em> garbage collection as follows: <OL><LI> Write a <tt>Handle</tt> class that contains the methods given below:<PRE>class Handle(Object): def getSize(self): "(Handle) -> int" # ... getReference(self, offset): "(Handle, int) -> Handle" # ... setReference(self, offset, handle): "(Handle, int, Handle) -> None" # ... def __getitem__(self, offset): "(Handle, int) -> int" # ... def __setitem__(self, offset, value): "(Handle, int, int) -> int" # ...</PRE> A handle refers to an object that contains either <tt>int</tt>s or other handles. The size of an object is total the number of <tt>int</tt>s and handles it contains. The various store and fetch methods are used to insert and remove items from the object to which this handle refers.<LI> Write a <tt>Heap</tt> class that contains the methods given below:<PRE>class Heap(object): def acquire(self, size): "(Heap, int) -> Handle" # ... def release (self, handle): "(Heap, Handle) -> None" # ... def collectGarbage(self): "(Heap) -> None" #</PRE> The <tt>acquire</tt> method allocates a handle and space in the heap for an object of the given size. The <tt>release</tt> method releases the given handle but does not reclaim the associated heap space. The <tt>collectGarbage</tt> method performs the actual garbage collection operation. </OL><LI> Using the approach described in Project <A HREF="page432.html#projectgarbageproject3"><IMG ALIGN=BOTTOM ALT="gif" SRC="../icons/cross_ref_motif.gif"></A>, implement a simulation of <em>mark-and-compact</em> garbage collection.<LI> Using the approach described in Project <A HREF="page432.html#projectgarbageproject3"><IMG ALIGN=BOTTOM ALT="gif" SRC="../icons/cross_ref_motif.gif"></A> implement a simulation of <em>reference-counting</em> garbage collection.</OL><P><HR><A NAME="tex2html6143" HREF="page433.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="../icons/next_motif.gif"></A> <A NAME="tex2html6141" HREF="page415.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="../icons/up_motif.gif"></A> <A NAME="tex2html6137" HREF="page431.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="../icons/previous_motif.gif"></A> <A NAME="tex2html6145" HREF="page611.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="../icons/index_motif.gif"></A> <P><ADDRESS><img src="../icons/bruno.gif" alt="Bruno" align=right><a href="../copyright.html">Copyright © 2003</a> by <a href="../signature.html">Bruno R. Preiss, P.Eng.</a> All rights reserved.</ADDRESS></BODY></HTML>⌨️ 快捷键说明
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