readme

主要应用于超大规模集成电路的布线算法

---------------------------------------

C-tree -- The construction of buffered Steiner trees for
          Difficult Instances

Author : Charles J. Alpert (IBM Austin Research Laboratory)
         C. N. Sze (Texas A&M University)
         Jiang Hu (Texas A&M University)

Copyright (c) 2003 
All rights reserved.

http://ece.tamu.edu/~cnsze/GSRC/ctree.html

Version : 1.0
Last updated : 2003 July 22
---------------------------------------

Important Notes 

    International Business Machines Corporation (IBM) holds the 
    patent (#6591411) of the C-tree techniques. Please refer to the patent
    page:

    <http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=6591411.WKU.&OS=PN/6591411&RS=PN/6591411>


NAME
    ctree - the C-tree implementation


SYNOPSIS

    ctree -i <input_file.net>
          [ -v ]
          [ -alpha <value> ]
          [ -beta <value> ]
          [ -clu_buf <res> <cap> <delay> ]
          [ -D <value> ]
          [ -o <output_file.net> ]
          [ -vg_buf <buffer.lib> ]

DESCRIPTION
    
    C-tree is a implementation for the construction of buffered Steiner trees
    which focus on the ``difficult instances'' which are characterized by a
    large number of sinks, large variation in sink criticalities nonuniform
    sink distribution, and varying polarity requirements.

PARAMETERS 

    [ -v ]
        verbose mode

    [ -alpha <value> ]
        set the parameter alpha in the equation of crit(). 
        This parameter is to control that how much amount of sinks will be
        treated as critical and all other non-critical sinks would have a
        similar value of crit().  
        Default = 2

    [ -beta <value> ]
        set the parameter beta in the equation of dist().
        This parameter is to balance the importance of spatial distance and
        temporal distance. A bigger beta value indicates that spatial distance
        is more important.
        Default = 0.65

    [ -clu_buf <res> <cap> <delay> ]
        set the buffer resistance, capacitance and intrinsic delay for the 
        achievable slack calculation in sink clustering step. Please note that
        this buffer information is not related to actual buffer insertion.

    [ -D <value> ]
        set the diameter threshold D which is used by the K-center heuristic.
        The heuristic is controlled by D -- we keep finding a new seed which
        is furthest from all other old seeds until the minimum distance from
        the new seed to all other old seeds is less than or equal to D. 
        Based on the distance equation, the maximum distance between two sinks 
        is 2 and so, if only one cluster is needed, set "-D 2".
        Default = 0.1

    -i <input_file.net>
        input file to ctree is a .net file which contains all the pin
        informations about the net as well as the technology parameter.
        see http://ece.tamu.edu/~cnsze/GSRC/ctree.html for more information.

    [ -o <output_file.out> ]
        if the output file is not specified, standard output will be used.
        ctree outputs the tree information (.out) including the physical
        location of all pins and Steiner points as well as their connections.
        It also outputs a (.log) log file which record the program activities,
        the CPU usage and the slack information.
        Default = result.out

    [ -vg_buf <buffer.lib> ]
        this option specifies the buffer library which is used by the final
        van Ginnekin style buffer insertion step.
        If the buffer library is not specified, the program will skip the
        buffer insertion step.

REFERENCE

    C. J. Alpert, M. Hrkic, J. Hu, A. B. Kahng, J. Lillis, B. Liu, S. T. Quay,
    S.  S. Sapatnekar, A. J. Sullivan, P. Villarrubia, ``Buffered Steiner
    trees for difficult instances'', IEEE Transactions on Computer-Aided
    Design of Integrated Circuits and Systems, Volume: 21 Issue: 1 , January
    2002, pp. 3-14

    http://ece.tamu.edu/~cnsze/GSRC/ctree.html