JAVAFO PAIRING ENGINE ADVANCED USER MANUAL
JaVaFo is both a stand‑alone program (provided that a java virtual machine exist to execute it) and an archive (.jar) that can be used by a program written in the java programming language.
This manual describes both possibilities.
In the following chapters, it will be described how it is possible for an external program to integrate the JaVaFo Pairing Engine in order to use it to prepare pairings according to the FIDE (Dutch) Swiss System (see section C.04.3 from FIDE Handbook).
Albeit JaVaFo supports many input formats (and other ones could be easily added), the most practical way to input data to JaVaFo is using the TRF(x), where TRF (also called TRF16 to distinguish it from the TRF06 used in the past), is the official FIDE Tournament Report File defined in the FIDE handbook (see), and the (x) stands for some extensions that have to be introduced in such format to make it useful for exchanging data between different programs. To be clearly understood by JaVaFo, it is recommended that such file is written using the UTF8 encoding.
The extensions to the TRF16 are partly made by adding some new codes (which are alphabetic in order to be completely different by the current numeric codes defined for the format), partly by allowing writing in the TRF something that is not normally found in a TRF, partly by interpreting some data contained in it.
A TRF is normally used only to generate data at the end of the tournament. The first extension is to allow the TRF to be generated also during the tournament. This partial TRF is fed to JaVaFo as its input.
It is important to note that the field called Points in the TRF16 definition (position 8184) contains the correct number of points that each player got, because that number is tentatively used to infer the scoring point system used (i.e. the classic 1, ½, 0 or another one, like 3, 1, 0; or even weirder ones ‑ for the complete list of values that JaVaFo tries to infer, see the scoringpoint parameters in the section Reducing randomness by way of a (RTG) configuration file ‑ scoringpoint parameters).
The partial TRF contains information regarding the rounds that have already been played. However it says nothing regarding the current round (i.e. the one that should be paired). The most important thing is to tell JaVaFo which players should be paired or, which is the same, which players will not play that round.
If everybody plays in the current round, the partial TRF is enough. Otherwise, if somebody is missing, there are two notcontrasting ways to pass this piece of information to the pairing engine.
The first one consists in inserting into the proper columns for the current round the result code that is normally used for absent players, i.e. "0000 Z".
For the sake of clarity, it is also possible to use the codes that will be present in the final TRF16 (i.e. "0000 H", for half‑point‑byes or "0000 F" for the deprecated fullpointbyes), but, in these cases, also the field Points (position 81‑84, see above) must be updated.
Blank codes are obviously ignored in this instance, as each present player is identified by the absence of a result code.
As said in the introduction regarding input data, some alphabetic codes were added in order to transmit additional information to the pairing engine. Some of them are not essential (and will be shown in a following chapter), but one is: the pairing engine must know the total number of rounds in the tournament in order to know if the current round is the last one.
This is obtained by means of the following new alphabetic code:
where number is the number of rounds of the competition.
In the linked file, there is an example of the TRF(x) used to pair the fifth round of the XX Open Internacional de Gros which includes everything said above regarding the TRF extensions.
According to what was discussed before, it should be pretty evident that the players 22, 26 and 43 will not play the fifth round (look at the field Points for the player 43, though).
Although, the title of this chapter is "JaVaFo as a standalone program", this terminology is highly simplicistic. In reality, JaVaFo is an executable java archive (jar), and here is described how to invoke a similar element.
First of all, a Java Virtual Machine (JVM) is needed. The beauty of this is that the operating system (O.S.) in use is not important. JaVaFo can run on any O.S. provided that a Java Virtual Machine exist in it. Be java the command to activate it.
Then the pairing engine itself, javafo.jar, is needed. The latest version of the jar can always be downloaded from the following web‑site:
You can also find previous versions of javafo.jar replacing current with 1.0, 1.1, 1.2 and so on. Be aware, though, that the releases until 1.4 do not follow the specification of this manual, but are tied to ancient versions of the Dutch Rules.
The downloaded jar archive can be stored anywhere in the file system. Be JVF_DIR the pathname of the folder where javafo.jar has been downloaded.
The first test to see if both the JVM and the pairing engine work is to write in a command prompt:
java ea jar JVF_DIR\javafo.jar (or)
java ea jar JVF_DIR/javafo.jar
depending on the O.S. in use. The first line works for Windows. From here on, only the Windows commands are mentioned. Moreover, for the full command java ea jar JVF_DIR/javafo.jar, the string javafo is used, as if a file named javafo.bat exists somewhere in a PATH directory and contains the statement:
If everything is properly set up, the above command should produce the following output (or something similar, more up‑to‑date):
JaVaFo (rrweb.org/javafo) ‑ Rel. 2.1 (Build 2952)
After checking that the pairing engine is ready, a TRF16 file can be input to it (a TRF06 will still work, but the output is not completely trustful). Even this file can be placed anywhere in the file system. Be TRF_DIR the pathname of the folder where the file trn.trfx is located (trn.trfx is just a mnemonic name; dummy.foo is an equally valid name).
It should be also decided where the pairing engine output goes. Be OUT_DIR\outfile.txt the pathname of said output file (as above, this file can be called in any way). Be aware that no warning is issued if the file pre‑exists before invoking javafo.jar.
From the same command prompt mentioned above, the following command line is needed to produce the pairings for the current round:
javafo TRF_DIR\trn.trfx p OUT_DIR\outfile.txt
The meaning of the most useful options will be described in a following chapter. But the above command is the most generic way to invoke the javafo.jar pairing engine. If OUT_DIR\ is the same than TRF_DIR\, then OUT_DIR can be dropped, so that
javafo TRF_DIR\trn.trfx ‑p outfile.txt
generates outfile.txt in TRF_DIR. If TRF_DIR is the current directory (i.e. "."), TRF_DIR\ can be dropped.
When invoked as shown in the previous command, the output is the file outfile.txt. The structure of this file is very simple:
 the first line reports the number of generated pairs (be P)
 from the second to the (P+1)th line, each line contains a pair for the current round. Such pair is made using the pairingid(s) of the players, i.e. the id(s) that are defined in the 001 line of the TRF(x). The first element of the pair gets white, the second one black. If the number of players to be paired in the round is odd, one of the pairs is formed by the id of the player that gets the pairingallocatedbye, followed by 0.
The TRF sample shown above will produce the following output:
If something goes wrong the output file is not generated. Something is usually displayed on standard output or standard error, but it may be quite difficult to interpret.
The most common cause for an error is a malformed TRF(x). However, if the TRF(x) is totally correct, than an error must have occurred in the pairing engine. This may occasionally happen, but it is a very unlikely event (although not an impossible one, of course).
What was presented in the previous chapters covers the majority of the situations that can happen in a tournament. Sometimes, however, something may happen that requires some extra care.
In Unusual info extensions, it has already been shown a way to register the players that are not going to be paired in a round. An alternative way is to use the extension code XXZ, the format of which is:
where the pairing‑id(s) following XXZ are intuitively the ones of the players that will miss the round to be paired.
There can be multiple XXZ records.
JaVaFo identifies players with two numbers, the playerid and the positionalid.
The first one is obvious and it is the one that is associated with the 001 record in the TRF(x). The second one is implicitly given by the position of the players in the TRF(x). Albeit this is not mandatory, players are normally inserted into the TRF(x) in accordance with their pairing‑id, so that the two sets of data (pairingid(s) and positionalid(s)) are basically coincident.
They may differ, though, and sometimes for good reasons. For instance, please give a look at the linked file, which is a modified version of the previous sample: the players with a local rating (0 for FIDE) are placed at the end of the list.
The positional‑id is 1 for Mirzoev, 6 for Lakunza (player‑id: 7), 29 for Aizpurua (player‑id: 32), 42 for Abalia (player‑id: 42), 48 for Gorrochategui (player‑id: 6) and so on.
JaVaFo computes the pairings using the pairingid(s). Beware: JaVaFo uses the pairingid(s), not the ratings, as specified by the FIDE (Dutch) rule A.2.b. This is a programming choice that cannot be modified.
However, the calling program is not forced to follow the same logics. If it desires that the rating be prevalent, it has two alternatives:
[a] before calling JaVaFo, redefine the pairingid(s) in such a way that increasing pairingid(s) are assigned to players with decreasing rating (which, by the way, is the most standard situation)
[b] insert players in the TRF(x) in order of rating and tell JaVaFo to use the positionalid(s) (also called rankingid(s)) instead of the pairingid(s)
The first choice is the recommended one. However, in order to let the calling program use the second alternative, JaVaFo provides the extension code:
The 'C' in XXC stands for configuration. The word rank tells JaVaFo to use the positionalid(s) in order to produce the pairings. The output file still contains the pairingid(s).
If the "XXC rank" clause is added to the file shown in the Ranked TRF(x) Sample, JaVaFo will return the following output:
which is different by the previous one (differences highlighted in red).
Although the rule for pairing the first round is very simple and therefore the calling program can generate it directly, it is recommended to use JaVaFo also to generate the first round.
The only information to pass to the pairing engine is the initial‑colour, as defined in the section E of the FIDE (Dutch) Rules. There are three possibilities:
[c] let JaVaFo make the choice (i.e. random)
The latter choice is the default. Beware that it is a semirandom choice: to compute it, JaVaFo uses the hash of some data taken from the TRF(x); this means that repeating the process with the same TRF(x) will give the same result each time. Therefore, in order to use the JaVaFo random choice, the calling program needs doing nothing.
Otherwise, to force the choice [a], the TRF(x) must contain a line
To force the choice [b], the TRF(x) must contain a line
Please note that the XXC code is cumulative, so it is followed by all the configuration choices made by the calling program. For instance:
XXC rank black1
is a valid extension line and combines what was described in the previous and in the current chapters.
The standard way to have accelerated rounds is to assign fictitious points to some players. How to assign such points depends on various methods and only one of them has been codified in the FIDE Handbook (see). Hence, this is not a matter of discussion here (on the other hand, see Baku Acceleration Method, below).
However, JaVaFo can be informed of the fictitious points that are assigned to each player, using the extension code XXA.
The format for this code is
XXA NNNN pp.p pp.p ...
= XXA starts at column 1
= NNNN (player's id ‑ same as in 001) starts at column 5
= pp.p (fictitious points) starts at column 10+5*(r1), where r is the round in which the fictitious points must be added
It is mandatory to keep the full record of the fictitious points assigned round by round, because this record is used to determine the floaters history of each player (actually, if pairing for round X, it is enough to maintain the fictitious points history from the rounds from X3 to the current one ‑ but it seems simpler, also from a pairingchecking standpoint, to keep the full history).
Here is an example from a real tournament where seven accelerated rounds were used:
Upon request, JaVaFo can pair the current round by applying the Baku Acceleration Method (see C.04.5.1 in the FIDE Handbook). In order to do so, JaVaFo should be invoked using the option ‑b.
Beware that JaVaFo applies the
Sometimes some players are to be prevented from meeting each other. JaVaFo can be directed to fulfill this need by means of the extension code XXP.
The format of this code is:
All the players mentioned in the list will not be paired against each other.
There is no limit on how many times a player can be part of a XXP list. So, for instance, if games between members of two groups of players cannot happen (for instance, assume that <13, 78, 102> and <68, 111> be these two groups), the following list of XXP extension codes should be generated:
XXP 13 68
XXP 13 111
XXP 78 68
XXP 78 111
XXP 102 68
XXP 102 111
Upon request, JaVaFo can generate a check‑list, i.e. a file that summarizes the situation after the pairing, with the following contents (taken from the previous TRF(x) sample):
In order to produce the check‑list, JaVaFo should be invoked using the option ‑l, optionally followed by the name of the file which to put the check‑list in. If such name is missing, JaVaFo will produce the file trn.list, provided that ‑l follow the input file name.
For instance, this works:
javafo TRF_DIR\trn.trfx ‑p OUT_DIR\outfile.txt ‑l
and this works too:
javafo TRF_DIR\trn.trfx ‑p OUT_DIR\outfile.txt ‑l ANY_DIR\outfile.list
As usual, if ANY_DIR is omitted, outfile.list is produced in the TRF_DIR.
As mentioned above, the simple command javafo will print the release version and build on the standard output.
If an input filename is specified, this information is not output unless the ‑r option is used.
JaVaFo can also be used to check the correctness of a TRF produced by other software: the command line:
javafo TRF_DIR\trn.trfx ‑c
will produce on standard output something similar to what is shown below (related to the tournament described by the TRF(x) Acceleration Sample), with obvious meaning:
In order to help an external pairing‑checker, JaVaFo can generate random or quasi‑random tournaments against which the external pairing‑checker can be tested.
The command line (in its simplest form):
javafo ‑g ‑o trn.trf
will generate in the current folder (any pathname like TEST_DIR\trn.trf can be specified, though) a file trn.trf, which is a TRF16 of a random tournament, with a random number of players (usually between 15 and 415), a random number of rounds (usually between 5 and 17) and game results that depend on the rating difference between the involved players, applying a formula elaborated by Otto Milvang (see here, Appendix A) that, in the long run, will distribute points based on what actually happens in rated tournaments.
In the same command line, the option ‑b (apply the
The most important utilization of this feature is to generate thousands of tournaments and then test them with the appropriate checker. Therefore it is advisable to use (on Windows) a statement like that:
@for /L %p IN (1000,1,5999) do @javafo ‑g ‑o test%p.trf
which will generate exactly 5000 random tournaments in the current folder.
The previously mentioned randomness in the generated files can be reduced in two alternative ways, using either a (RTG) configuration file or a model TRF.
A (RTG) configuration file is a property‑file where the following parameters (properties) may be defined (for the explanation of each single parameter, please look at the sample below):
An example of a (RTG) configuration file (with comments) is shown here:
In order to being used by the JaVaFo Random Tournament Generator, the (RTG) configuration file must be specified as a parameter to the ‑g option. Therefore, the full command line is:
javafo ‑g RTG_DIR\rtg.cfg ‑o TEST_DIR\trn.trf (or)
javafo ‑g RTG_DIR\rtg.cfg ‑b ‑o TEST_DIR\trn.trf
if there is the desire to apply, when feasible, the Baku Acceleration Method.
A model tournament is a normal input TRF file with meaningful player ratings, which serves as a model in order to define all the parameters mentioned above.
For instance, from the input file seen in the TRF(x) Acceleration Sample, the following values are automatically retrieved:
Note that the ratings parameters HighestRating, LowestRating, Groups and Separator are not considered, as the ratings are exactly the same as the ones present in the input model file, while the scoring‑points parameters are not shown as their value is equal to the corresponding default value.
As the model file is a standard input file, the command line to use it is:
javafo MODEL_DIR\model.trf ‑g ‑o TEST_DIR\trn.trf
It is also possible to add the option ‑b (apply
The square brackets [ ] represent something optional.
As an experimental tool, with versions 2.x, it is possible to include parts of JaVaFo in a Java project and have the possibility to directly interface JaVaFo as a pairing engine, a free pairing‑checker or a random‑tournament‑generator.
The first operation is to open javafo.jar (which is an archive that can be usually opened with the same tools that open .zip or .rar files) and extract the file main.jar. The latter is the file to be included in a Java project. It exposes a static class, JaVaFoApi, that contains the definition of a method that can be called to invoke, depending on the parameters, the pairing engine, the pairing checker or the random generator.
The aforementioned method is:
String JaVaFoApi.exec(int operation, Object... params);
that will execute the most common operations of JaVaFo (and a few others).
The first parameter (operation) may assume one of the following values:
Then the parameter list of JaVaFoApi.exec may contain the following parameters in any order (it is their Java type that identifies them):
String out = JaVaFoApi.exec(1301, inputStreamTRF, 6);
Return into out the TRF of a random‑generated‑tournament
String out = JaVaFoApi.exec(1210, 6, new FileInputStream("C:\jvfck\trnXDW.trf"));
Return into out the result of the verification of the 6th round of the tournament described by the TRF file C:\jvfck\trnXDW.trf.
String out = JaVaFoApi.exec(1110, outputStream, trf);
Return thru the outputStream output‑stream the post‑pairing check‑list for the tournament of which the TRF is contained in the trf string. In out it is returned null.
Note: it is possible to use the above operation to retrieve the pairing of the round, but it is not a very practical way to do it.
JaVaFoApi.exec(1000, "Hello World", inputStreamTRF, outputStream);
Return thru the outputStream output‑stream the pairings for the tournament of which the TRF has been read thru the inputStreamTRF input‑stream. The string "Hello World" is ignored.
Properties cfg = new Properties();
JaVaFoApi.exec(1300, cfg, new FileOutputStream("C:\jvfgen\trP289R9.trf");
Put into the file c:\jvfgen\trP289R9.trf the TRF of a random‑generated‑tournament with 289 players and 9 rounds.
 The idea of alphabetic codes comes from the author of the TRF, Christian Krause, chairman of the Systems of Pairings and Programs (SPP) FIDE Commission
 A property-file is a file where empty lines have no meaning and lines introduced by the symbol # contain a comment.
The meaningful lines have the format PropertyName=PropertyValue, which assigns to the named property (or parameter) the value specified by PropertyValue.