GNU Backgammon F.A.Q.

This file documents the most frequently asked questions. Source are the newsgroup rec.games.backgammon, the gnubg-mailinglist and the bulletin board of Kit Woolseys online magazine GammOnLine.

Copyright © 2002 Achim Mueller.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".

1. General questions
2. How to install
3. Starting gnubg
4. Playing backgammon
5. Settings
6. Analysing
7. Databases
8. Abbreviations
9. GNU Free Documentation License

Table of Contents

1. General questions

1.1 What is GNU Backgammon?
1.2 What operating systems are supported?
1.3 Where do I get it?
1.4 What do I have to pay for GNU Backgammon?
1.5 This GNU stuff sounds interesting.
1.6 I want to learn more about backgammon.
1.7 Though I really read all the documentation I still have questions.
1.8 I want to make a few proposals. I have new ideas.
1.9 This F.A.Q. is full of typos and in bad English.

2. How to install

2.1 Where do I find an installable version for my operating system?
2.2 Do I need some other software to run GNU Backgammon?
2.3 I want to install a newer version.
2.4 I would like to compile it from the source code.
2.5 What software do I need for compiling under GNU/Linux?
2.6 What software do I need for compiling under MS Windows?
2.7 It does not compile.

3. Starting gnubg

3.1 I get an error message when starting.
3.2 GNU Backgammon complains about missing files.
3.3 Starting from the WinXP menu she plays like a beginner.
3.4 My screen mixes up while starting GNU Backgammon.
3.5 I only get a command-line interface. Where is the nice Board
3.6 When I restart GNU Backgammon all my settings are gone.
3.7 I do not need this graphical stuff. Where is the terminal for commands?

4. Playing backgammon

4.1 What is the difference of a new game or match or session?
4.2 What the heck is a beaver in Backgammon?
4.3 How do I move the checkers?
4.4 Why am I allowed to place more than 5 checkers on a spot?
4.5 GNU Backgammon plays poorly.
4.6 GNU Backgammon is to strong for me.
4.7 I think the bot is cheating. She always gets good dice.

5. Settings

5.1 Where can I change the name of the human player?
5.2 How do I change the colours?
5.3 How do I stop the annoying beeps?"
5.4 What are "Plies?"
5.5 What is "noise?"
5.6 What is "reduced evaluation?"

6. Analysing

6.1 What are these funny letters at the right bottom?
6.2 How do I set up a position manually?
6.3 Which formats must I use to import positions?
6.4 Which formats must I use to import matches?
6.5 How can I switch the players sides?
6.6 What does "!" and "?" mean?
6.7 How is the error rate determined?

7. Databases

7.1 What is the `Database' menu for?
7.2 "There are no target evaluations in the database to train from."
7.3 What is `Train with TD(0)'?

8. Abbreviations

8.1 "gwc"?
8.2 "mwc"?
8.3 "dp"?
8.4 "tg"?

9. GNU Free Documentation License

A.0 ADDENDUM: How to use this License for your documents

1. General questions

1.1 What is GNU Backgammon?
1.2 What operating systems are supported?
1.3 Where do I get it?
1.4 What do I have to pay for GNU Backgammon?
1.5 This GNU stuff sounds interesting.
1.6 I want to learn more about backgammon.
1.7 Though I really read all the documentation I still have questions.
1.8 I want to make a few proposals. I have new ideas.
1.9 This F.A.Q. is full of typos and in bad English.

1.1 What is GNU Backgammon?

GNU Backgammon (gnubg) is for playing and analysing backgammon positions, games and matches. It's based on a neural network. Though it already plays on a very high level, it's still work in progress. You may play GNU Backgammon using the command line or a graphical interface (based on GTK+).

1.2 What operating systems are supported?

Currently GNU Backgammon is actually designed for GNU/Linux. It also compiles and (hopefully) runs under *BSD, IRIX, Solaris and True64 Unix. Last but not least there are frequently binaries for MS Windows and MS DOS. Porting to MacOS is planned but not yet released. When you successfully port GNU Backgammon to other operating systems you are welcome to give us a note at bug-gnubg@gnu.org.

1.3 Where do I get it?

The official website is http://www.gnu.org/software/gnubg/gnubg.html. You can get daily snapshots at ftp://alpha.gnu.org/gnu/gnubg/snapshots/. MS Windows binaries are available at http://home.online.no/%7Eoeysteij/. GNU/Linux-Rpm's are (hopefully) soon available at acepoint's home.

1.4 What do I have to pay for GNU Backgammon?

GNU Backgammon is Open Source Software and belongs to the GNU Project. You may download it for free. For more information see the GNU General Public License. But be aware that GNU Backgammon is not public domain software or shareware as you perhaps know from MS Windows.

1.5 This GNU stuff sounds interesting.

Take a look at the GNU's homepage.

1.6 I want to learn more about backgammon.

A good place to start is The Backgammon Galore. For an extensive link collection go to Gammon-links.

1.7 Though I really read all the documentation I still have questions.

Send an email to the gnubg-mailinglist. If it is a bug, be sure to include a reference of your operating system, the version of gnubg you use and possible error messages you get. Try to describe exactly what happens, before the error occurs.

1.8 I want to make a few proposals. I have new ideas.

You're welcome! Send an email with your suggestions to gnubg-mailinglist.

1.9 This F.A.Q. is full of typos and in bad English.

Probably you are right. But you are cordially invited to send corrections to acepoint@deltacity.net. And keep the following quote in mind ;-):

Documentation is like sex: when it is good, it is very, very good, and when it is bad, it is better than nothing.

[ Dick Brandon ]

2. How to install

2.1 Where do I find an installable version for my operating system?
2.2 Do I need some other software to run GNU Backgammon?
2.3 I want to install a newer version.
2.4 I would like to compile it from the source code.
2.5 What software do I need for compiling under GNU/Linux?
2.6 What software do I need for compiling under MS Windows?
2.7 It does not compile.

2.1 Where do I find an installable version for my operating system?

For MS Windows go to this place. GNU/Linux-Rpm's are (hopefully) soon available at acepoint's home.

2.2 Do I need some other software to run GNU Backgammon?

No. All stuff you need is included in the binaries.

2.3 I want to install a newer version.

If you are using a MS Windows operating system make a copy of either `.gnubgrc' or `.gnubgautorc' and `.gnubgmenurc'. You will find them either in `c:' or the home directory of your GNU Backgammon (for instance: `c:\program files\gnubg\'). After you have installed the new version, copy them back.

If you are working with GNU/Linux these files are probably in your home directory (`~/'). They won't be overwritten by installing a new version of GNU Backgammon. But it's always a good idea to have a backup of them.

2.4 I would like to compile it from the source code.

Good luck to you! Download the source code and make sure to read one of the following two items: 2.5 What software do I need for compiling under GNU/Linux?, 2.6 What software do I need for compiling under MS Windows?.

2.5 What software do I need for compiling under GNU/Linux?

Depending on the distribution you are working with:

• GNU Backgammon snapshots
• a "C-"compiler
• autoconf and automake
• xdevel (for the graphical interface)
• gtk+ >= 1.2 (for the graphical interface)
• gtk+-devel
• guile (optional, for invoking your own macros)
• guile-devel
• gdbm (optional, for using your own databases)
• gdbm-devel

Unpack the GNU Backgammon snapshots and follow the instructions of the file `INSTALL'.

2.6 What software do I need for compiling under MS Windows?

Nardy Pillards has published a fine instruction guide at http://users.skynet.be/bk228456/GNUBgW.htm. Go to this page and follow the steps shown there.

2.7 It does not compile.

Check that you have installed all necessary development packages. For

GNU/Linux:2.5 What software do I need for compiling under GNU/Linux?,

and for

MS Windows:2.6 What software do I need for compiling under MS Windows? should be listed all you probably want.

Look for warnings or errors during compiling. If you still don't get a clue, send a message to the gnubg-mailinglist.

3. Starting gnubg

3.1 I get an error message when starting.
3.2 GNU Backgammon complains about missing files.
3.3 Starting from the WinXP menu she plays like a beginner.
3.4 My screen mixes up while starting GNU Backgammon.
3.5 I only get a command-line interface. Where is the nice Board
3.6 When I restart GNU Backgammon all my settings are gone.
3.7 I do not need this graphical stuff. Where is the terminal for commands?

3.1 I get an error message when starting.

Well, your computer wants to communicate with you. Give him a chance and read (and try to understand) what he is telling you. Then read the next items carefully ....

3.2 GNU Backgammon complains about missing files.

GNU Backgammon is probably either missing the file `gnubg.weights' or `gnubg.bd'. `Gnubg.bd' is the bearoff database that gnubg uses to evaluate endgame positions.

The file `gnubg.weights' contains the trained neural net weights for most of gnubg's position evaluators. Like `gnubg.bd', it should be kept in either the current directory or the installed directory.

3.3 Starting from the WinXP menu she plays like a beginner.

Open the MS Windows menu and go to the entry of gnubg. Right-click with the mouse and choose `properties'. Check, if the `working path' is the same directory as the `*.exe'-file one line above. If not, adjust the working path.

3.4 My screen mixes up while starting GNU Backgammon.

Install the newest driver for your graphic card. Be sure that you have chosen at least a desktop resolution of 65535 (16 bit colour depth). If your card is a ATI Rage "somewhat" there still might be some problems with the graphical interface (GTK+)and MS Windows.

3.5 I only get a command-line interface. Where is the nice Board

Using MS Windows just click on the correct menu entry (`GNU Backgammon for windows'). If it still doesn't work, check whether `c:\[path-to-your-gnubg]\gnubg.exe' exists or not.

GNU/Linux users should check if GTK+ is installed.

3.6 When I restart GNU Backgammon all my settings are gone.

Did you save your settings (menu `Settings, Save settings') before? If you have just installed a newer version of GNU Backgammon go to 2.3 I want to install a newer version.

3.7 I do not need this graphical stuff. Where is the terminal for commands?

For GNU/Linux users: open a terminal and start gnubg with the option `-t'.

MS Windows users: Look for a file called `gnubg-no-gui.exe' in gnubg's directory or open the MS Windows menu `execute' and type `c:\[path-to-your-gnubg]\gnubg-no-gui.exe'. There is also a menu entry `GNU Backgammon Command Line Interface'.

4. Playing backgammon

4.1 What is the difference of a new game or match or session?
4.2 What the heck is a beaver in Backgammon?
4.3 How do I move the checkers?
4.4 Why am I allowed to place more than 5 checkers on a spot?
4.5 GNU Backgammon plays poorly.
4.6 GNU Backgammon is to strong for me.
4.7 I think the bot is cheating. She always gets good dice.

4.1 What is the difference of a new game or match or session?

When you start a new match you will be asked to play to a certain amount of points (for example: 7 points). The player who firstly reaches this amount wins the match.

Starting a new session means playing to an infinite amount. Be aware that the rules do slightly differ then. You may break this session at every point and save it.

If you choose to play a new game, GNU Backgammon will open the last saved match or session you quit. When there is no saved match or session you will start a new infinite session.

4.2 What the heck is a beaver in Backgammon?

A beaver is only allowed in a moneygame session. To beaver means redoubling (and keeping the cube) directly after your opponent doubled. For more information go to Backgammon Galore (Glossary).

4.3 How do I move the checkers?

The easiest way to move chequers is to "drag and drop." Put your mouse pointer to a chequer you want to move, press the left mouse button and drag the chequer to the desired point (hold down the button while dragging).

If you want to use mouse clicks you have to know, that the left mouse button is for the left die shown on your board. Right click your mouse for the right die.

For always getting the higher number on the left go to the menu `Settings, Appearance, General' and activate `Show higher die on left.'

4.4 Why am I allowed to place more than 5 checkers on a spot?

The official backgammon tournament rules allow to put all 15 chequers on a pip (spot). If you want to play with a maximum of 5 chequers, go to the menu `Settings' and activate the `Egyptian Rule.'

4.5 GNU Backgammon plays poorly.

Are you sure? If the answer is yes you should think about going to Monte Carlo this summer and win the Backgammon World Championship.

If this plan fails, check whether `gnubg.weights' is correctly installed. See also 3.2 GNU Backgammon complains about missing files.

4.6 GNU Backgammon is to strong for me.

Go to the menu `Settings, Players' and change the values of `Player 0'. There is also a set of predefined settings you may choose from.

4.7 I think the bot is cheating. She always gets good dice.

In the menu `Settings' you may choose between different random dice generator. If you still think GNU Backgammon is cheating, program your own dice generator or roll manually.

5. Settings

5.1 Where can I change the name of the human player?
5.2 How do I change the colours?
5.3 How do I stop the annoying beeps?"
5.4 What are "Plies?"
5.5 What is "noise?"
5.6 What is "reduced evaluation?"

5.1 Where can I change the name of the human player?

Go to the menu `Settings, Players ...' and click on `Player 1'. At the top there is a field to change the human players name.

5.2 How do I change the colours?

5.3 How do I stop the annoying beeps?"

Go to the menu `Settings, Appearance' and click on the card `General' at the right. Disable the option `Beep on illegal input'.

5.4 What are "Plies?"

A ply describes how far GNU Backgammon evaluates the position. "0-ply" means, GNU Backgammon estimates the worth of the position as it is. A "1-ply" evaluation looks one step deeper. GNU Backgammon also evaluates positions that may occur one roll further. "2-ply" is another roll further and so on.

The more plies you choose the more you strengthen GNU Backgammon. But keep in mind that it will also decrease her playing speed.

Note also that "0-ply" in GNU Backgammon is equivalent to the "1-ply" evaluation of Snowie.

5.5 What is "noise?"

Noise is nothing but kind of disturbing GNU Backgammons 0-ply evaluation. Rising the noise decreases her playing strength.

5.6 What is "reduced evaluation?"

Reduced searches only work with 2-ply evaluations and deeper. It somehow cuts the searching for candidates to increase speed.

6. Analysing

6.1 What are these funny letters at the right bottom?
6.2 How do I set up a position manually?
6.3 Which formats must I use to import positions?
6.4 Which formats must I use to import matches?
6.5 How can I switch the players sides?
6.6 What does "!" and "?" mean?
6.7 How is the error rate determined?

6.1 What are these funny letters at the right bottom?

You will find two small windows titled `Position' and `Match ID' at the bottom of the GNU Backgammon window. Here you may use the `position_id'- or `match_id'-format for setting up or copying positions.

An explanation of both formats will follow in GNU Backgammon's documentation (hopefully soon).

6.2 How do I set up a position manually?

Open a new game, match or session. If gnubg already rolls the dice, don't bother. Press `edit' and either type the position_id and press Enter at your keyboard. Or use the mouse to set up the chequers.

A mouse click at the border of the board empties the pip. A left (right) mouse click sets up a certain amount of chequers depending on where exactly on the pip you click. Set up the cube with a right mouse click on it.

At last go to the menu `Game, Set turn' and choose the player on roll. The dice will disappear then.

6.3 Which formats must I use to import positions?

Currently only `*.pos' by Jellyfish are supported.

6.4 Which formats must I use to import matches?

You may import `*.mat' by Jellyfish or `*.ssg' by Gamesgrid. Also supported is the oldmove format used on Fibs.

6.5 How can I switch the players sides?

Go to the menu `Game and click on Swap players'.

6.6 What does "!" and "?" mean?

After analysing a game or a match GNU Backgammon is able to do some comments on chequer play or cube decisions. Open the menu `Window, Game record' and you will see a list of the moves. If the actual move or cube decision differs from the best, GNU Backgammon will put a comment on it.

The default settings are:

+0.040 (very good):	Not in use yet
+0.020 (good):	Not in use yet
-0.040 (doubtful):	?!
-0.080 (bad):	?
-0.160 (very bad):	??

You may change these comment in the menu `Window, Annotation' choosing another comment for moves and/or double.

6.7 How is the error rate determined?

GNU Backgammon determines the players strength as follows: If a player has an average error (per move) of:

< 0.005 --->	Extra-terrestrial
< 0.010 --->	World class
< 0.015 --->	Expert
< 0.020 --->	Advanced
< 0.025 --->	Intermediate
< 0.030 --->	Novice
> 0.030 --->	Beginner

After analysing a game, match or session you can see the summary in the menu `Analyse, ... statistics'. Note that you can't change the ranges of these values.

7. Databases

7.1 What is the `Database' menu for?
7.2 "There are no target evaluations in the database to train from."
7.3 What is `Train with TD(0)'?

7.1 What is the `Database' menu for?

In the menu `Train, Generate database' GNU Backgammon will play against herself (0-ply with `gnubg.weights') generating a position database. This database will be automatically saved as `gnubg.gdbm' when you press the button `stop' at the left side.

After the database is generated you may use `Train, Rollout database' to do a 36-trial rollout of all positions. Then you may train `gnubg.weights' with the new evaluated positions using `Train, Train database'.

7.2 "There are no target evaluations in the database to train from."

You have forgotten to rollout the database before. See 7.1 What is the `Database' menu for?.

7.3 What is `Train with TD(0)'?

This will train the network by TD(0) using zero-knowledge self-play.

8. Abbreviations

8.1 "gwc"?
8.2 "mwc"?
8.3 "dp"?
8.4 "tg"?

8.1 "gwc"?

"gwc" is an abbreviation for game winning chances.

8.2 "mwc"?

"mwc" is an abbreviation for match winning chances.

8.3 "dp"?

In the menu `Analyse, Game/Match/Session statistics' you will see a window with some statistics. Near the bottom you'll see four lines beginning with `Missed ... and Wrong ...'. "dp" means "doubling point" and describes a situation in the game, where you probably should have doubled your opponent.

8.4 "tg"?

"tg" is an abbreviation for "too good". It points to a situation in the game, where you probably should have kept the cube (mostly because of huge gammon chances) rather than doubling out your opponent.

9. GNU Free Documentation License

Copyright © 2000 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

1. PREAMBLE

   The purpose of this License is to make a manual, textbook, or other written document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

   This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

   We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

2. APPLICABILITY AND DEFINITIONS

   This License applies to any manual or other work that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you".

   A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

   A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (For example, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

   The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License.

   The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License.

   A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, whose contents can be viewed and edited directly and straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup has been designed to thwart or discourage subsequent modification by readers is not Transparent. A copy that is not "Transparent" is called "Opaque".

   Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML designed for human modification. Opaque formats include PostScript, PDF, proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML produced by some word processors for output purposes only.

   The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

3. VERBATIM COPYING

   You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

   You may also lend copies, under the same conditions stated above, and you may publicly display copies.

4. COPYING IN QUANTITY

   If you publish printed copies of the Document numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

   If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

   If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a publicly-accessible computer-network location containing a complete Transparent copy of the Document, free of added material, which the general network-using public has access to download anonymously at no charge using public-standard network protocols. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

   It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

5. MODIFICATIONS

   You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

   1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.

   2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has less than five).

   3. State on the Title page the name of the publisher of the Modified Version, as the publisher.

   4. Preserve all the copyright notices of the Document.

   5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.

   6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.

   7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.

   8. Include an unaltered copy of this License.

   9. Preserve the section entitled "History", and its title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.

   10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.

   11. In any section entitled "Acknowledgments" or "Dedications", preserve the section's title, and preserve in the section all the substance and tone of each of the contributor acknowledgments and/or dedications given therein.

   12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.

   13. Delete any section entitled "Endorsements". Such a section may not be included in the Modified Version.

   14. Do not retitle any existing section as "Endorsements" or to conflict in title with any Invariant Section.

   If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

   You may add a section entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

   You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

   The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

6. COMBINING DOCUMENTS

   You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice.

   The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

   In the combination, you must combine any sections entitled "History" in the various original documents, forming one section entitled "History"; likewise combine any sections entitled "Acknowledgments", and any sections entitled "Dedications". You must delete all sections entitled "Endorsements."

7. COLLECTIONS OF DOCUMENTS

   You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

   You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

8. AGGREGATION WITH INDEPENDENT WORKS

   A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, does not as a whole count as a Modified Version of the Document, provided no compilation copyright is claimed for the compilation. Such a compilation is called an "aggregate", and this License does not apply to the other self-contained works thus compiled with the Document, on account of their being thus compiled, if they are not themselves derivative works of the Document.

   If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one quarter of the entire aggregate, the Document's Cover Texts may be placed on covers that surround only the Document within the aggregate. Otherwise they must appear on covers around the whole aggregate.

9. TRANSLATION

   Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License provided that you also include the original English version of this License. In case of a disagreement between the translation and the original English version of this License, the original English version will prevail.

10. TERMINATION

    You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

11. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

A.0 ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

Copyright (C) year your name. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being list their titles, with the Front-Cover Texts being list, and with the Back-Cover Texts being list. A copy of the license is included in the section entitled ``GNU Free Documentation License''.

If you have no Invariant Sections, write "with no Invariant Sections" instead of saying which ones are invariant. If you have no Front-Cover Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being list"; likewise for Back-Cover Texts.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.

About this document

• 1. Section One
• 1.1 Subsection One-One
• ...
• 1.2 Subsection One-Two
• 1.2.1 Subsubsection One-Two-One
• 1.2.2 Subsubsection One-Two-Two
• 1.2.3 Subsubsection One-Two-Three     <== Current Position
• 1.2.4 Subsubsection One-Two-Four
• 1.3 Subsection One-Three
• ...
• 1.4 Subsection One-Four