Trail (JaCoP 4.9.0 API)

java.lang.Object
- org.jacop.jasat.core.Trail

All Implemented Interfaces:

SolverComponent
```
public final class Trail
extends Object
implements SolverComponent
```
It stores the current variables status (affected or not, with which value and explanation). It values of variables are packed in an int, together with the level at which they were asserted.

Version:

4.9

Author:

Simon Cruanes and Radoslaw Szymanek

Field Summary

Fields
Modifier and Type Field and Description

IntStack assertionStack

int[] explanations

MemoryPool pool

int[] values

Fields
Modifier and Type	Field and Description
`IntStack`	`assertionStack`
`int[]`	`explanations`
`MemoryPool`	`pool`
`int[]`	`values`

Constructor Summary

Constructors
Constructor and Description

Trail()

Constructors
Constructor and Description
`Trail()`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addVariable(int var)` It adds a variable to the trail.
`void`	`assertLiteral(int literal, int level)` Sets a literal, that is, a variable signed with its value (> 0 for true, < 0 for false).
`void`	`assertLiteral(int literal, int level, int causeId)` Sets a literal, with an explanation clause.
`void`	`backjump(int level)` It tells the trail to return to given level.
`void`	`ensureCapacity(int numVar)` It ensures the trail can contain @param numVar variables
`int`	`getExplanation(int var)` It returns the index of the clause that caused this variable to be set
`int`	`getLevel(int var)` It returns the level at which @param var has been set.
`void`	`initialize(Core core)` to be called before any use of the trail
`boolean`	`isAsserted(int var)` It returns information if a variable was asserted or only propagated.
`boolean`	`isSet(int var)` predicate which meaning is : is this variable set or unknown ?
`int`	`size()` returns the number of currently set variables
`String`	`toString()`
`void`	`unset(int var)` It unsets the given variable.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - pool
```
public MemoryPool pool
```
  - values
```
public int[] values
```
  - explanations
```
public int[] explanations
```
  - assertionStack
```
public IntStack assertionStack
```
- Constructor Detail
  - Trail
```
public Trail()
```
- Method Detail
  - addVariable
```
public void addVariable(int var)
```
    It adds a variable to the trail.
    
    Parameters:
    
    var - the variable
  - ensureCapacity
```
public void ensureCapacity(int numVar)
```
    It ensures the trail can contain @param numVar variables
    
    Parameters:
    
    numVar - the number of variables the trail must be able to contain
  - assertLiteral
```
public void assertLiteral(int literal,
                          int level)
```
    Sets a literal, that is, a variable signed with its value (> 0 for true, < 0 for false). This must be used only for asserted values, not the ones propagated from unit clauses.
    
    Parameters:
    
    literal - the literal
    
    level - the current level
  - assertLiteral
```
public void assertLiteral(int literal,
                          int level,
                          int causeId)
```
    Sets a literal, with an explanation clause. For unit propagation only.
    
    Parameters:
    
    literal - the literal (non nul relative number)
    
    level - the level at which this assertion occurs
    
    causeId - the ID of the clause that triggered this assertion
  - unset
```
public void unset(int var)
```
    It unsets the given variable. Does not take car of assertionLevels !
    
    Parameters:
    
    var - the variable to unset. Must be positive.
  - backjump
```
public void backjump(int level)
```
    It tells the trail to return to given level. It will therefore erase all assertion strictly above this level. Literals asserted at @param level will be kept.
    
    Parameters:
    
    level - the level to jump to.
  - getLevel
```
public int getLevel(int var)
```
    It returns the level at which @param var has been set. @param var *must* be set, otherwise this will fail.
    
    Parameters:
    
    var - the literal which level we wish to know
    
    Returns:
    
    the level
  - getExplanation
```
public int getExplanation(int var)
```
    It returns the index of the clause that caused this variable to be set
    
    Parameters:
    
    var - the literal. Must be set.
    
    Returns:
    
    an index if there was an explanation, 0 otherwise
  - isAsserted
```
public boolean isAsserted(int var)
```
    It returns information if a variable was asserted or only propagated.
    
    Parameters:
    
    var - the variable
    
    Returns:
    
    true if the variable was asserted
  - isSet
```
public boolean isSet(int var)
```
    predicate which meaning is : is this variable set or unknown ?
    
    Parameters:
    
    var - the variable, must be positive
    
    Returns:
    
    true if the variable is set.
  - size
```
public int size()
```
    returns the number of currently set variables
    
    Returns:
    
    the number of currently set variables
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - initialize
```
public void initialize(Core core)
```
    to be called before any use of the trail
    
    Specified by:
    
    initialize in interface SolverComponent
    
    Parameters:
    
    core - the Solver instance

Class Trail

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

pool

values

explanations

assertionStack

Constructor Detail

Trail

Method Detail

addVariable

ensureCapacity

assertLiteral

assertLiteral

unset

backjump

getLevel

getExplanation

isAsserted

isSet

size

toString

initialize