CASPP_LAB/traces/README

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# CS:APP Malloc Lab
# Traces
#
# Copyright (c) 2002, R. Bryant and D. O'Hallaron, All rights reserved.
# May not be used, modified, or copied without permission.
#
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This directory contains traces of allocate and free requests that are
used by the test harness to evaluate the student malloc packages.

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1. Files
*********

*.rep		Original traces
*-bal.rep	Balanced versions of the original traces
gen_XXX.pl	Perl script that generates *.rep	
checktrace.pl	Checks trace for consistency and outputs a balanced version
Makefile	Generates traces

Note: A "balanced" trace has a matching free request for each allocate
request.

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2. Building the traces
**********************
To rebuild the traces from scratch, type 

	unix> make

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3. Trace file format
********************

A trace file is an ASCII file. It begins with a 4-line header:

<sugg_heapsize>   /* suggested heap size (unused) */
<num_ids>         /* number of request id's */
<num_ops>         /* number of requests (operations) */
<weight>          /* weight for this trace (unused) */

The header is followed by num_ops text lines. Each line denotes either
an allocate [a], reallocate [r], or free [f] request. The <alloc_id>
is an integer that uniquely identifies an allocate or reallocate
request.

a <id> <bytes>  /* ptr_<id> = malloc(<bytes>) */
r <id> <bytes>  /* realloc(ptr_<id>, <bytes>) */ 
f <id>          /* free(ptr_<id>) */

For example, the following trace file:

<beginning of file>
20000
3
8
1
a 0 512
a 1 128
r 0 640
a 2 128
f 1
r 0 768
f 0
f 2
<end of file>

is balanced. It has a recommended heap size of 20000 bytes (ignored),
three distinct request ids (0, 1, and 2), eight different requests
(one per line), and a weight of 1 (ignored).

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4. Description of traces
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* short{1,2}-bal.rep

Tiny synthetic tracefiles for debugging

* {amptjp,cccp,cp-decl,expr}-bal.rep

Traces generated from real programs.

* {binary,binary2}-bal.rep

The allocation pattern is to alternatively allocate a small-sized
chunk of memory and a large-sized chunk. The small-sized chunks
(either 16 or 64 ) are deliberately set to be power of 2 while the
large-size chunks (either 112 or 448) are not a power of 2. Defeats
buddy algorithms. However, a simple-minded algorithm might prevail in
this scenario because a first-fit scheme will be good enough.

* coalescing-bal.rep

Repeatedly allocate two equal-sized chunks (4095 in size) and release
them, and then immediately allocate and free a chunk twice as big
(8190). This tests if the students' algorithm ever really releases
memory and does coalescing. The size is chosen to give advantage to
tree-based or segrated fits algorithms where there is no header or
footer overhead.

* {random,random2}-bal.rep
	
Random allocate and free requesets that simply test the correctness
and robustness of the algorithm.


* {realloc,realloc2}-bal.rep
	
Reallocate previously allocated blocks interleaved by other allocation
request. The purpose is to test whether a certain amount of internal
fragments are allocated or not. Naive realloc implementations that
always realloc a brand new block will suffer.