Ogame probabilistic battle engine
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Ogame Probabilistic Battle Engine
live: http://opbe.altervista.org
2moons running opbe: http://testopbe.altervista.org

Require PHP >= 5.3


  1. Introduction
  2. Quick start
  3. Accuracy
  4. Performance
  5. TestCases
  6. Developers guide
  7. License
  8. Questions
  9. Who is using OPBE


OPBE is the first (and only) battle engine in the world that uses Probability theory:
battles are processed very very fast and required little memory resources.
Also, memory and CPU usage are O(1), this means they are CONSTANT and independent of the ships amount.


  • Multiple players and fleets (ACS)
  • Fake targets (Fodder)
  • Rapid fire
  • Randomic rapid fire with normal distribution
  • Ordered fires
  • Bounce rule
  • Waste of damage
  • Moon attempt
  • Plunder algorithm (resources partition)
  • Defenses rebuilt
  • Report generated by templates
  • Report can be stored as object in database
  • Cross-platform (XgProyect,2moons,Xnova,Wootook etc)

Future features

  • automatic Bcmath detect and usage if needed

Quick start (installation)

This seems so cool! How can I use it?
You can check in implementations directory for your game version, read the installation.txt file.
Be sure you have read the license with respect for the author.


One of main concepts used in this battle engine is the expected value: instead calculate each ship case, OPBE creates an estimation of their behavior.
This estimation is improved by analyzing behavior for infinite simulations, so, to test OPBE's accuracy you have to set speedsim (or dragosim)'s battles amount to a big number, such as 3k.
Recently was added a feature to simulate a randomic rapid fire, making the combat more realistic. Anyway you can enable or disable it inside the constants/battle_constants file.
Note: randomic rapid fire will only change the amount of shots,but the way it do is particularly...Infact the deviaton from the mean is made by a special random number generator implementing Gauss algorithm.
This ensure a bell curve of shots close to the ideality.
Also,the system can be bounded by values that can be setted in the constants/battle_constants* file.


It seems that noone knows the O() notation, so this is the definition from the Wiki:
big O notation is used to classify algorithms by how they respond (e.g., in their processing time or working space requirements) to changes in input size.
There are different possibilities, such as O(n) (linear), O(n^2) (quadratic) etc.
OPBE is O(1) in both CPU and MEMORY usage:
In practice, that means that the computional requirements to solve an algoritm don't increase with the input size.
It's awesome! You can simulate 20 ships or 20 Tera ships and nothing should change.
In reality, there is a small difference because the arithmetic operations aren't O(1) for CPU, and also a double requires more space than an integer.

Let's do some test:

Double's limit test

Write a lot of nines in both defender's BC and attacker's BC.
Because of the double limit, your number will be trunked to 9223372036854775807.
Anyway the battle starts and are calculated as well (some overflow errors maybe).

Battle calculated in 2.54 ms.
Memory used: 335 KB
Worst case, OPBE max requirements!

The only thing that requires a lot of memory in OPBE is the Report, because it stores all ships in every round... this means that more
rounds = more memory.
Also, the worst case for CPU and memory is to have all types of ships(iteration of them).
So we set 1'000'000 of ships in each type(defenses only for defender),not a big number just to avoid overflow in calculations.
And we got:

Battle calculated in 144.88 ms.
Memory used: 6249 KB
  • These values really depend on your hardware and PHP configuration: expecially, caching the bytecode will decrease a lot the CPU usage but increase RAM usage.

Seems a lot? Try a O(n^2) algorithm and you will crash with insane small amount of ships :)
Anyway you can decrease a lot the memory usage setting, in constants/battle_constants.php,


Making new test cases to share

Something wrong with OPBE? The fastest way to share the simulation is to make a test case.

  1. Set your prefered class name,but it must extends RunnableTest.
  2. Override two functions:
  • getAttachers() : return a PlayerGroup that rappresent the attackers
  • getDefenders() : return a PlayerGroup that rappresent the defenders
  1. Instantiate your class inside the file.
  2. Put the file in opbe/test/runnable/

An example:

require ("../RunnableTest.php");
class MyTest extends RunnableTest
    public function getAttachers()
        $fleet = new Fleet(1,array(
            $this->getShipType(206, 50),
            $this->getShipType(207, 50),
            $this->getShipType(204, 150)));
        $player = new Player(1, array($fleet));
        return new PlayerGroup(array($player));
    public function getDefenders()
        $fleet = new Fleet(2,array(
            $this->getShipType(210, 150),
            $this->getShipType(215, 50),
            $this->getShipType(207, 20)));
        $player = new Player(2, array($fleet));
        return new PlayerGroup(array($player));
new MyTest();
  • You can check the combat result entering with a browser in opbe/test/runnable/MyTest.php
  • Please use Github issue system

Implementation developing guide

The system organization is like :

  • PlayerGroup
    • Player1
    • Player2
      • Fleet1
      • Fleet2
        • ShipType1
        • ShipType2

So in a PlayerGroup there are different Players,
each Player have different Fleets,
each Fleet have different ShipTypes.

  • All these classes implements Iterator interface, so you can iterate them as arrays.

     foreach($playerGroup as $idPlayer => $player)
          foreach($player as $idFleet => $fleet)
              foreach($fleet as $idShipType => $shipType)
                  // do something

    But to increase performace it's better to call getIterator() function.

  • Another good point is that there aren't side effects in all OPBE classes. This means something like this:

class A
    private $store=array();
    function put($id,$object)
       $this->store[$id] = $object->clone();
    function get($id) 
        return $this->store[$id];    

$a= new A();
$obj = new Object();
$obj->x= "hello";

$obj->x .=" word"; // $object is edited only outside A, no side effects!

echo $a->get(1); // print "hello" instead "hello world"  

Sometimes it's not really required to clone, but this good practice ensure less bugs.


ShipType is the smallest unit in the system: it reppresents a group of specific object type able to fight.
For some reasons, OPBE needs to categorize it in either one of these two types extending ShipType:

  • Defense
  • Ship

You shouldn't ened to care about this fact because this automatic code will do it for you:

    $shipType =  $this->getShipType($idShipType, $count);
function getShipType($id, $count)
    global $CombatCaps, $pricelist;
    $rf = $CombatCaps[$id]['sd'];
    $shield = $CombatCaps[$id]['shield'];
    $cost = array($pricelist[$id]['metal'], $pricelist[$id]['crystal']);
    $power = $CombatCaps[$id]['attack'];
    if ($id >= SHIP_MIN_ID && $id <= SHIP_MAX_ID)
        return new Ship($id, $count, $rf, $shield, $cost, $power);
    return new Defense($id, $count, $rf, $shield, $cost, $power);
  • Note that you can assign different technology levels to each ShipType, see functions inside this class.
  • By default, ShipType will give tech levels by its Fleet container .


Fleet is a group of ShipType and it is extended by a single object

  • HomeFleet : represent the ships and defense in the target's planet

This time you have to manually choose the right class and HomeFleet should have $id = 0;

    $fleet = new Fleet($idFleet); // $idFleet is a must
    $fleet = new HomeFleet(0); // 0 is a must
  • Note that you can assign differents techs to each Fleet, see functions inside this class.
  • By default, Fleet will give tech levels by its Player container .
  • HomeFleet work as Fleet, but with the difference that is unique: adding more HomeFleet will result on merging them. Feature implemented just for a better report.
  • Fleet has a __toString method that automatically fill-up the corrispective views/fleet.html and return the result html.
    So you can echo it.
  echo $fleet; 


Player is a group of Fleets, don't care about the question attacker or defender.

    $player = new Player($idPlayer); // $idPlayer is a must
  • Player has a __toString method that automatically fill-up the corrispective views/player2.html and return the result html.
    So you can echo it.
  echo $player; 


PlayerGroup is a group of Player, don't care about the question attacker or defender.

    $playerGroup = new PlayerGroup();
  • PlayerGroup has a __toString method that automatically fill-up the corrispective views/PlayerGroup.html and return the result html.
    So you can echo it.
  echo $playerGroup; 

Bring them together

An easy way to display them:

    $fleet = new Fleet($idFleet);
    $fleet->addShipType($this->getShipType($id, $count));
    $player = new Player($idPlayer);
    $playerGroup = new PlayerGroup();


Battle is the main class of OPBE.
The first argument of constructor is the attacking PlayerGroup, the second one is the defending PlayerGroup.

There are two methods you need to know about:

  • startBattle(boolean $debug) : start the battle, if $debug == true, informations will be written in output.
  • getReport() : return an object useful to retrieve all kinds of battle information.
    $engine = new Battle($attackingPlayerGroup, $defendingPlayerGroup);
    $info = $engine->getReport();


BattleReport is a big container of data about the simulated battle.
In the web interface of OPBE, the instance of BattleReport is injected in templates.

    $info = $engine->getReport();
  • BattleReport contains all the ships status in every round, and also has useful functions to fill templates or update
    the database after the battle.
  • BattleReport has a __toString method that automatically fill-up the corrispective views/report.html and return the result html.
    So you can echo it.
   echo $info; 

This is very usefull to store only the object in database and generate the html when needed. For example:

    $obj = serialize($info);
    mysql_query("INSERT INTO Reports (id , obj) VALUES ($id, $obj)");
    $result = mysql_fetch_array(mysql_query("SELECT obj FROM Reports WHERE id = $id"));    
    $info = unserialize($result['obj']);
    echo $info;



Copyright (C) 2013  Jstar

OPBE is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.

OPBE is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

why affero GPL


I would like to include your battle engine but the code of my game won't be published

You can keep secret your code because OPBE can be seen as a external module with own license, it's only required to share changes on OPBE.

I would like to have some profits with my game

GNU affero v3 accepts profits as well

I would like use OPBE with numbers greater than double

You should replace any PHP native mathematical with BC math functions

I would like change ships/defense repair probability

    You have to change only constats/battle_constants.php  
    define('DEFENSE_REPAIR_PROB', 0.7); // 0.7 = 70%
    define('SHIP_REPAIR_PROB', 0);

Who is using OPBE?

I'm happy to deliver this software giving others the possibility to have a good battle engine.
On the other hand, it's a pleasure to see people using my OPBE.
Send me an email to put your game logo here! frascafresca@gmail.com