ngspice/FAQ

  Ngspice F.A.Q.Version 1.4
  Maintained by Paolo Nenzi <p.nenzi@ieee.org>
  Last update: 27-01-2004

  This document contains the Frequently Asked Questions (and Answers)
  for ngspice project.
  __________________________________________________________________________

  Table of Contents


  1. INTRODUCTION AND GENERAL INFORMATION
     1.1 What is ngspice?
     1.2 Why resurrecting Berkeley's Spice?
     1.3 What is the project's goal?
     1.4 What you are going to do?
     1.5 Legal issues
     1.6 What mailing lists exist for ngspice?
     1.7 Are the mailing lists archived anywhere?
     1.8 What newsgroups exist for ngspice?
     1.9 Where can I get a copy of ngspice?
     1.10 Where should I look on the World Wide Web for ngspice stuff?
     1.11 Where should I look on the World Wide Web for Spice documentation?

  2. DEVELOPMENT
     2.1 What is the current version?
     2.2 What are the latest features in the current release?
     2.3 What does it look like?
     2.4 Who are the authors of ngspice?
     2.5 How can I report a bug/request for a feature?
     2.6 How can I join the development?

  3. SOLUTIONS TO COMMON MISCELLANEOUS PROBLEMS
     3.1 What systems are supported?
     3.2 I get errors when I try to compile the source code, why?
     3.3 This document didn't answer my question. Where else can I look for
         an answer?

  4. ADMINISTRATIVE INFORMATION AND ACKNOWLEDGEMENTS
     4.1 Feedback
     4.2 Formats in which this FAQ is available
     4.3 Authorship and acknowledgements
     4.4 Disclaimer and Copyright


  ______________________________________________________________________

  1.  INTRODUCTION AND GENERAL INFORMATION



 1.1 What is ngspice?

  Ngspice is a mixed-level/mixed-signal circuit simulator based on three 
  open source software packages: Spice3f5, Cider1b1 and Xspice: 
  
  - Spice3 is the most famous and used circuit simulator. It was 
    developed University of California at Berkeley (UCB), by "a cast of 
    thousand" (as they say).
  
  - Cider is a mixed-level simulator that already includes Spice3f5 and 
    adds a device simulator to it: DSIM. Cider couples the circuit level 
    simulator to the device simulator to provide greater simulation 
    accuracy (at the expense of greater simulation time). Critical 
    devices can be described with technology parameters (numerical 
    models) and non critical ones with the original spice's compact 
    models.

  - Xspice is an extension to Spice3 that provides code modeling support 
    and simulation of digital components through an embedded event 
    driven algorithm.

  The NG prefix has lot of meanings: Next Generation, New Good, etc. 
  Choose or invent the one you prefer. The heart of the project is the 
  ngspice program.


 1.2 Why resurrecting Berkeley's Spice?
  
  Berkeley's Spice can be considered the father of most circuit
  simulators available today. It is an old but still good piece of
  software, it may not be the fastest or the most reliable but it's
  free, it's available in source code and most of the electrical
  simulators inherited it's syntax. On the more technical side, spice3
  uses good numerical algorithms (most commercial implementations have
  only strengthened them), implements most of the models for MOSFET
  submicron designs and has a powerful set of analyses. On the more
  "social" side, spice3 it's well introduced in the academic
  environment.

 
 1.3 What is the project's goal?

  The project goal evolved during project development, at first the
  final goal was to develop a reliable, fast and friendly circuit 
  simulator for mixed signal/mixed level simulation. During 
  development it become apparent that to reach the goal a complete
  rewrite of spice was needed. Since it was almost absurd to rewrite
  Spice and since a new simulator was already under development:
  ACS (Al's Circuit Simulator), now GNUCap (GNU Circuit Analysis
  package), the goal of nspice became less utopical: merge
  Spice3f5, Xspice and Cider into a mixed-signal/mixed-level simulator
  that can be used as a reliable engine.  


 1.4 What you are going to do?  

  We are going to develop a mixed-signal/mixed-level circuit simulation
  program integrating three different spice based simulators:
  Spice, Xspice and Cider.
  
  Xspice is a mixed-signal circuit simulator developed by GTRI (Georgia 
  Tech Research Institute) at Georgia Institute of Technology. Xspice
  was originally developed as an extension over Spice3c1. Xspice
  introduces code modeling and a digital simulator into ngspice.
  The "home site" of Xspice is: 
  
           http://users.ece.gatech.edu/~mrichard/Xspice/
  
  Cider is a mixed-level circuit and device simulator based on Spice3f5
  that couples a device simulator (DSIM) to Spice. More information can
  be found at:
  
        http://www-cad.eecs.berkeley.edu/Software/cider.html 
  
  The merging process is done in parallel with bug fixing and improvement
  of the three simulators. The improvements are concentrated into 6
  directions:
  
  
  + Compact models:  the improvements in compact models will address
    mainly the implementation of additional effects not available
    in the original code. Device specific improvements are documented
    on ngspice's documentation and in the DEVICE file in project's
    tarball.
    Improvements that affects all devices already implemented are:
    "dtemp" option to set instance's temperature relative to the circuit 
    one and "m" parallel multiplier to simulate an arbitrary number of
    instances of the same kind connected in parallel.
    
    Planned improvements are the development of a dynamic loading
    mechanism for compact models, to avoid loading in memory devices
    that are not needed, and SOAR (Safe Operating ARea) checks to 
    identify situations in which devices are used out of their
    safety areas.  
  
  
  + Simulator's analyses: this is a low priority area. Planned improvements
    include the implementation of parametric analyses, to analyse the
    behaviour of the circuit as a parameter changes. Parameter sweep,
    Monte Carlo and Worst Case fall in this category. Network analysis
    (double bipole parameters extraction) is another planned improvement.       
    
  
  + Numerical analysis code: the improvements within the numerical code
    must be done with extreme care. Planned improvements are, the 
    replacement of the Sparse library with the latest code Kenneth Kundert
    has released, available at:

               http://sourceforge.net/projects/sparse
   
   Other planned improvements, but with very low priority, includes the
   use SuperLU library as possible Sparse library replacement (the 
   library is available at http://crd.lbl.gov/~xiaoye/SuperLU) and the
   introduction of continuation metohds to aid DC convergence. 
  
  
  + Spice language: The language used to input the circuit to the simulator
    has been extended and now allows the user to input parametric values
    for components (the numparam library). This is an experimental feature 
    that will be improved in the future. Planned improvements includes the
    support for loading more than one circuit, netlist manipulation via
    command line (adding and removing instances) and the implementation
    of a command history using the libedit library, available at:
     
                 http://sourceforge.net/projects/libedit
    
  
  + Frontend: The design of a new spice frontend has not been successful
    and now is orphaned, since the is no interests and many free and
    commercial frontends are available. There is no planned improvement
    here.
    
  
  + Documentation: Commercial simulators come with very good manuals 
    containing tutorials, description of models equations, example of 
    use, suggestions, etc. Spice came with little documentation. The 
    Spice3f manual, available on the Internet has been used as the basis
    for the new manual. It will be constantly improved during ngspice 
    development and integrated with the documentation accompanying Xspice 
    and Cider. This is a very time consuming task and probably the 
    documentation will always be left slightly behind.
   

 1.5 Legal issues

  Ngspice merges three different simulators: spice and cider are covered
  with the "old" BSD license, Xspice by its own license. The ngspice 
  license will be then the BSD license. 
  
  Since the "old" BSD license is not compatible with the GPL library
  it is not possible to link the ngspice with GPL'ed code, as is
  written in:
  
             http://www.gnu.org/philosophy/bsd.html
   
  The group developing ngspice has written to Berkeley's copyright 
  holders asking to change the license to the new BSD, which has the 
  incompatibility removed, but without success. 
  
  Ngspice will not be released under GPL license and, no GPL code can be 
  linked into ngspice (as in the original Spice3f) without breaking GPL.


 1.6.  What mailing lists exist for ngspice?

  There are three mailing lists dedicated to the ngspice project. 
  
  Users mailing list: <ngspice-users@lists.sourceforge.net>
  This list is for ngspice users, examples, problems, bug reports
  and general discussion on ngspice can be sent here
  
  Developers mailing list: <ngspice-devel@lists.sourceforge.net>
  The list dedicated to ngspice development. Developers shold 
  subscribe here, to follow the program development. May be used
  to send patches, and technical discussion on ngspice. 
  
  Frontend mailing list: <ngspice-frontends@lists.sourceforge.net>
  Almost orphaned, this list should be used to discuss issues about 
  the realization of a graphical frontend to ngspice. 
  
  Send an empty message to the following addresses to get information 
  on subscription.  
  
  <ngspice-users-help@lists.sourceforge.net>

  <ngspice-devel-help@lists.sourceforge.net>

  <ngspice-frontends-help@lists.sourceforge.net>


 1.7.  Are the mailing lists archived anywhere ?

  Yes, the lists are archived. There are two places where to look for
  archives. The project started on the IEEE Central and South Italy
  web server and then moved to sourceforge. Sourceforge provides an
  archiving service that cam be accessed via the summary page:
  
                     http://sourceforge.net/projects/ngspice
  
  (look for the "Lists" link). Old messages from the pre-sourceforge 
  age are available at:
  
                    http://ngspice.sourceforge.net/lists.html    


 1.8.  What newsgroups exist for ngspice?

  There is no ngspice specific newsgroup. Anyway ngspice threads appear
  on newsgroups dedicated to circuit simulation and electronic design.
  An (incomplete) list is:
  
  sci.electronics.cad
  comp.lsi.cad 


 1.9.  Where can I get a copy of ngspice?

  You can download ngspice from:

                      http://sourceforge.net/projects/ngspice


 1.10.  Where should I look on the World Wide Web for ngspice stuff?

  Look at the official Ngpice Web Page:
  
                           http://ngspice.sourceforge.net


 1.11.  Where should I look on the World Wide Web for Spice documenta-
         tion?

  There are a lot of Internet sites that have information on spice, the
  best way is to point to your preferred search engine. Some interesting
  sites are:
  
  The Spice Home Page:
   http://bwrc.eecs.berkeley.edu/Classes/IcBook/SPICE/
  
  Xspice Page:
   http://users.ece.gatech.edu/~mrichard/Xspic

  Cider Page:
   http://www-cad.eecs.barkeley.edu/Software/cider.html
   
  Spice benchmarks:
   http://www.cbl.ncsu.edu/pub/Benchmark_dirs
    


  2.  DEVELOPMENT


 2.1.  What is the current version?

  The latest version released is: 
  
  * ngspice-rework-15 (released on 10/12/2001)
  
  The development version is:
  
  * ngspice-rework-15pre3 (released on 28/01/2004)


 2.2.  What are the latest features in the current release?

  New features:


    + Improved bipolar devices (Diode and bjt)
    + Improved BSIM3 and BSIM4
    + VBIC and HiSIM compact models
    + Cider and Xspice inclusion
    + More flexibility in net names
    + Parameter substitution in netlist

  Bug fixes:

    + Many memory leaks closed
    + Control language works as expected


 2.3.  What does it looks like?

  Ngspice, as the original Spice3 (and Xspice and Cider) is a command
  line simulator.


 2.4.  Who are the authors of ngspice?

  The development is open to anyone who wish to contribute. If the 
  original Spice3 was made with the contribution of "a cast of 
  thousand", ngspice can only increase that number. An incomplete
  list of contributor makes the "acknowledgements" page of ngspice
  documentation.  


 2.5.  How can I report a bug/request for a feature?

  The ngspice summary page (hosted on Sourceforge) has bug-reporting,
  feature-request and bugs trackers. You can use them or subscribe to
  mailing lists and post there. The latter is preferred since almost
  all developers/contributors read the lists but only a few of them
  use trackers.

 
 2.6.  How can I join the development?

  To join the development just code the feature you want to add and send
  your patch in the mailing list.  Before you start coding check the
  latest development release of ngspice from our CVS. It might be that
  your feature has already been implemented.
  
  There is no bureaucracy here.



  3.  SOLUTIONS TO COMMON MISCELLANEOUS PROBLEMS


 3.1.  What systems are supported?

  Ngspice is written in C, and uses some GNU extensions, then you need
  a GNU C compiler and a UNIX environment to compile it. Ngspice can
  be compiled under Windows using  the mingw or cigwin environment.
  
  In the future a compatibility table will be written.


 3.2.  I get errors when I try to compile the source code, why?
  
  This is a one-million-euros question :). 
  
  Write a mail to the user's list describing the problem and providing
  information on the type of hardware, the flavour of operating system.


 3.3.  This document didn't answer my question. Where else can I look
        for an answer?
	
  Read old messages from the mailing list archive, search the web site
  or read the docs.  Upgrade to the latest version of ngspice, many
  problems are fixed in the new versions.  If you still can't find an
  answer, post your question to the mailing lists.



  4.  ADMINISTRATIVE INFORMATION AND ACKNOWLEDGEMENTS


 4.1.  Feedback

  Send your comments about this F.A.Q. to:

  Paolo Nenzi <p.nenzi@ieee.org>.

  Send your comments about ngspice to:

  Paolo Nenzi <p.nenzi@ieee.org>.


 4.2.  Formats in which this FAQ is available

  This document is available only in ASCII format in the ngspice source
  package.


 4.3.  Authorship and acknowledgements

  Parts of the questions and answers are originate from Paolo Nenzi.


 4.4.  Disclaimer and Copyright

  This document is provided as is. The information in it is not
  warranted to be correct: you use it at your own risk.