SPEC CPU2000 Benchmark Description File
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Benchmark Name:
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181.mcf
Benchmark Author:
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Dr. Andreas Loebel
Konrad-Zuse-Zentrum Berlin (ZIB)
Takustr. 7
D-14195 Berlin, Germany
E-mail: loebel@zib.de
Phone: +49 (0)30 841 85 - 239
Fax: - 269
Secretary: - 208
Benchmark Program General Category:
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Combinatorial optimization / Single-depot vehicle scheduling
Benchmark Description:
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A benchmark derived from a program used for single-depot vehicle scheduling in
public mass transportation. The program is written in C, the benchmark version
uses almost exclusively integer arithmetic.
The program is designed for the solution of single-depot vehicle scheduling
(sub-)problems occurring in the planning process of public transportation
companies. It considers one single depot and a homogeneous vehicle fleet. Based
on a line plan and service frequenciesd, so-called timetabled trips with fixed
departure/arrival locations and times are derived. Each of this timetabled trip
has to be serviced by exactly one vehicle. The links between these trips are
so-called dead-head trips. In addition, there are pull-out and pull-in trips for
leaving and entering the depot.
Cost coefficients are given for all dead-head, pull-out, and pull-in trips. It
is the task to schedule all timetabled trips to so-called blocks such that the
number of necessary vehicles is as small as possible and, subordinate, the
operational costs among all minimal fleet solutions are minimized.
For simplification in the benchmark test, we assume that each pull-out and
pull-in trip is defined implicitly with a duration of 15 minutes and a cost
coefficient of 15.
For the considered single-depot case, the problem can be formulated as a
large-scale minimum-cost flow problem that we solve with a network simplex
algorithm accelerated with a column generation. The core of the benchmark
181.mcf is the network simplex code "MCF Version 1.2 -- A network simplex
implementation", For this benchmark, MCF is embedded in the column generation
process.
The network simplex algorithm is a specialized version of the well known simplex
algorithm for network flow problems. The linear algebra of the general algorithm
is replaced by simple network operations such as finding cycles or modifying
spanning trees that can be performed very quickly. The main work of our network
simplex implementation is pointer and integer arithmetic.
Input Description:
-----------------
The input file contains line by line
- the number of timetabled and dead-head trips (first line),
- for each timetabled trip its starting and ending time,
- for each dead-head trip its starting and ending timetabled trip and its cost.
Worst case execution time is pseudo-polynomial in the number timetabled
and dead-head trips and in the amount of the maximal cost coefficient.
The expected execution time, however, is in the order of a low-order polynomial.
The benchmark requires about 100 and 190 megabyte for a 32 and a 64 bit
architecture, respectively.
Output Description:
------------------
The benchmark writes to two output files, inp.out and mcf.out. inp.out contains
log information and a checksum, mcf.out contains check output values describing
an optimal schedule computed by the program.
Programming Language:
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ANSI C, mathematical library (libm) required.
Known portability issues:
------------------------
The header source file "prototyp.h", which is (indirectly) required by all
modules, contains the lines
#ifndef _PROTO_
#if defined(__STDC__) || defined(__cplusplus) || defined(WANT_STDC_PROTO)
#define _PROTO_( args ) args
#else
#define _PROTO_( args )
#endif
#endif
All C functions (subroutines) are defined in the original program with and
without function prototypes, e.g.:
/* function defined externally: */
extern long suspend_impl _PROTO_(( network_t *, cost_t, long ));
/* function defined in this module: */
#ifdef _PROTO_
long resize_prob( network_t *net )
#else
long resize_prob( net )
network_t *net;
#endif
In the SPEC version, -DWANT_STDC_PROTO is set as a required compilation flag in
the master Makefile 181.mcf/src/Makefile. This has the effect that all
compilers, predefining __STDC__ or not, use ANSI C prototyping. This is intended
for reasons of compatibility and standard adherence.
Other information, WWW Resources:
--------------------------------
Background information about the vehicle scheduling problem can be found in the
author's Ph.D. thesis "Optimal Vehicle scheduling in public transit", which is
available via WWW at the author's homepage www.zib.de/loebel or at
ftp://ftp.zib.de/pub/zib-publications/books/Loebel.disser.ps.
The work horse in the benchmark 181.mcf is the code "MCF Version 1.2 -- A
network simplex implementation", which is available for academic use free of
charge via WWW at www.zib.de.
An excellent text book about the network simplex algorithm and network flow in
general is Ahuja, Magnanti, and Orlin: "Network Flows: Theory, Algorithms, and
Applications", Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1993.