# AMPL Class¶

An AMPL translator. An object of this class can be used to do the following tasks:

Run AMPL code. See ampl.AMPL.Eval and ampl.AMPL.EvalAsync.

Read models and data from files. See ampl.AMPL.read, ampl.AMPL.ReadData, ampl.AMPL.ReadAsync and ampl.AMPL.ReadDataAsync.

Solve optimization problems constructed from model and data (see ampl.AMPL.Solve and ampl.AMPL.SolveAsync).

Access single elements of an optimization problem. See the generic ampl.AMPL.GetEntity and the generic ampl.AMPL.GetVariable, ampl.AMPL.GetObjective, ampl.AMPL.GetConstraint, ampl.AMPL.GetSet and ampl.AMPL.GetParameter.

Access lists of available elements of an optimization problem. See ampl.AMPL.GetVariables, ampl.AMPL.GetObjectives, ampl.AMPL.GetConstraints, ampl.AMPL.GetSets and ampl.AMPL.GetParameters.

AMPL stores one or more problems which may consume substantial amount of memory. An AMPL object without any references to it will eventually be freed by the Java garbage collector and all the memory and other resources associated with it will be released. This includes any resources which are out of scope of the garbage collector such as open files or memory managed by the native code. Call ampl.AMPL.Close to release these resources explicitly.

The initialisation of the Java representation of the AMPL entities (any class derived from ampl.Entities.Entity) is lazy and consists of two steps. When a function listing available elements is called, only a shallow list with names, types and declarations of the elements is populated. The same happens when a reference to a Java representation of one entity is obtained (through a call to ampl.AMPL.GetEntity or any other single entity factory function). When accessing any instance of an entity (through the methods ‘get’ of any class), the (memory hungry) list of instances for that entity is created.

Consistency is maintained automatically. Any command issued to the translator through ampl.AMPL.Eval and similar functions invalidates all entities, and any further access to any entity will require communication between the native translator and the Java code. Conversely, any operation called through the Java equivalent function, like fixing variables or solving the model will invalidate only the entities involved. A list of dependencies between entities is automatically updated.

Error handling is two-faced:

1. Errors coming from the underlying AMPL translator (e.g. syntax errors and warnings obtained calling the ampl.AMPL.Eval method) are handled by the event ampl.AMPL.Error. Note that by default the event is disabled. To enable it, call ampl.AMPL.EnableErrorAndWarningRouting.

2. Generic errors coming from misusing the API, which are detected in .NET, are thrown as exceptions.

The default implementation of the error handler throws exceptions on errors and prints to console on warnings.

The output of every user interaction with the underlying translator is handled by the event ampl.AMPL.Output, which is called at each block of output from the translator after the function ampl.AMPL.EnableOutputRouting is called.

Namespace
ampl
Assemblies
• AMPL

## Syntax¶

public class AMPL : IDisposable

class ampl.AMPL

## Constructors¶

AMPL()

Default constructor: creates a new AMPL instance with the default environment.

public AMPL()

AMPL(ampl.Environment)

Creates a new AMPL instance with the specified environment

public AMPL(Environment e)


## Methods¶

Cd(System.String)

Change or display the current working directory (see https://en.wikipedia.org/wiki/Working_directory ).

Arguments: directoryName (System.String) – New working directory or null (to display the working directory) System.String
public string Cd(string directoryName = null)

Close()

Stops the underlying engine and release its resources. Any further attempt to execute optimisation commands without restarting it will throw an exception.

public void Close()

Display(System.String[])
public void Display(params string[] args)

Dispose()
public void Dispose()

Dispose(System.Boolean)
protected virtual void Dispose(bool disposing)

EnableErrorAndWarningRouting()

Enable routing of AMPL error and warning handling via the C# wrapper. Must be called to enable handling of errors and warning through handlers registered with ampl.AMPL.Error and ampl.AMPL.Warning.

public void EnableErrorAndWarningRouting()

EnableOutputRouting()

Enable routing of AMPL console outputs through the C# wrapper. Must be called to enable handling of the output through a personalised handler registered with ampl.AMPL.Output.

public void EnableOutputRouting()

Eval(System.String)

Parses AMPL code and evaluates it as a possibly empty sequence of AMPL declarations and statements. As a side effect, it invalidates all entities (as the passed statements can contain any arbitrary command); the lists of entities will be re-populated lazily (at first access) The output of interpreting the statements is passed to the current OutputHandler (see getOutputHandler and setOutputHandler). By default, errors are reported as exceptions and warnings are printed on stdout. This behavior can be changed reassigning an ErrorHandler using setErrorHandler.

Arguments: AMPLStatements (System.String) – A collection of AMPL statements and declarations to be passed to the interpreter
public void Eval(string AMPLStatements)

EvalAsync(System.String, System.Action)

Interpret asynchronously the given AMPL statements

Arguments: cb (System.Action) – Call back to be executed when completed
public void EvalAsync(string AMPLStatements, Action cb)

Expand(ampl.Entities.Entity[])
public void Expand(params Entity[] entities)

GetBoolOption(System.String)

Get the current value of the specified boolean option.

Arguments: name (System.String) – Option name System.Nullable{System.Boolean} The option value, null if the specified option does not exist
public bool ? GetBoolOption(string name)

GetConstraint(System.String)

Get the constraint with the corresponding name

Arguments: name (System.String) – Name of the constraint to be found ampl.Entities.Constraint
public Constraint GetConstraint(string name)

GetConstraints()

Get the defined constraints

Return type: ampl.Entities.ConstraintMap
public ConstraintMap GetConstraints()

GetData(System.String[])

<p>Get the data corresponding to the display statements. The statements can be AMPL expressions, or entities. It captures the equivalent of the command: </p> <p> <code>display ds1, …, dsn;</code> </p> <p> where<code> ds1, …, dsn </code>are the <span class=”paramref”>statements</span> with which the function is called. </p> <p>As only one DataFrame is returned, the operation will fail if the results of the display statements cannot be indexed over the same set. As a result, any attempt to get data from more than one set, or to get data for multiple parameters with a different number of indexing sets will fail.</p>

Arguments: statements (System.String[]) – The display statements to be fetched ampl.DataFrame DataFrame capturing the output of the display command in tabular form
public DataFrame GetData(params string[] statements)

GetDblOption(System.String)

Get the current value of the specified option.

Arguments: name (System.String) – Option name System.Nullable{System.Double} The option value, null if the specified option does not exist
public double ? GetDblOption(string name)

GetEntity(System.String)

Get entity corresponding to the specified name (looks for it in all types of entities)

Arguments: name (System.String) – Name of the entity ampl.Entities.Entity The AMPL entity with the specified name
public Entity GetEntity(string name)

GetIntOption(System.String)

Get the current value of the specified option.

Arguments: name (System.String) – Option name System.Nullable{System.Int32} The option value, null if the specified option does not exist
public int ? GetIntOption(string name)

GetObjective(System.String)

Get the objective with the corresponding name

Arguments: name (System.String) – Name of the objective to be found ampl.Entities.Objective
public Objective GetObjective(string name)

GetObjectives()

Get the defined objectives

Return type: ampl.Entities.ObjectiveMap
public ObjectiveMap GetObjectives()

GetOption(System.String)

Get the current value of the specified option.

Arguments: name (System.String) – Option name System.String The option value, null if the specified option does not exist
public string GetOption(string name)

GetParameter(System.String)

Get the parameter with the corresponding name

Arguments: name (System.String) – Name of the parameter to be found ampl.Entities.Parameter
public Parameter GetParameter(string name)

GetParameters()

Get the defined parameters

Return type: ampl.Entities.ParameterMap
public ParameterMap GetParameters()

GetSet(System.String)

Get the set with the corresponding name

Arguments: name (System.String) – Name of the set to be found ampl.Entities.Set
public Set GetSet(string name)

GetSets()

Get the defined sets

Return type: ampl.Entities.SetMap
public SetMap GetSets()

GetValue(System.String)

Get a scalar value from the underlying AMPL interpreter, as a double or a string.

Arguments: scalarExpression (System.String) – An AMPL expression which evaluates to a scalar value. ampl.Variant
public Variant GetValue(string scalarExpression)

GetVariable(System.String)

Get the variable with the corresponding name

Arguments: name (System.String) – Name of the variable to be found ampl.Entities.Variable
public Variable GetVariable(string name)

GetVariables()

Get the defined variables

Return type: ampl.Entities.VariableMap
public VariableMap GetVariables()

Interrupt()

Interrupt an underlying asynchronous operation (execution of AMPL code by the AMPL interpreter). An asynchronous operation can be started via evalAsync(), solveAsync(), readAsync() and readDataAsync(). Does nothing if the engine and the solver are idle.

public void Interrupt()

Read(System.String)

Interprets the specified file (script or model or mixed) As a side effect, it invalidates all entities (as the passed file can contain any arbitrary command); the lists of entities will be re-populated lazily (at first access)

Arguments: filename (System.String) – Path to the file (Relative to the current working directory or absolute)
public void Read(string filename)

ReadAsync(System.String, System.Action)

Interprets the specified file asynchronously, interpreting it as a model or a script file. As a side effect, it invalidates all entities (as the passed file can contain any arbitrary command); the lists of entities will be re-populated lazily (at first access)

Arguments: filename (System.String) – Path to the file (Relative to the current working directory or absolute) cb (System.Action) – Callback to be executed when the file has been interpreted
public void ReadAsync(string filename, Action cb)

ReadData(System.String)

Interprets the specified data file. As a side effect, it invalidates all entities (as the passed file can contain any arbitrary command); the lists of entities will be re-populated lazily (at first access)

Arguments: filename (System.String) – Path to the file (Relative to the current working directory or absolute)
public void ReadData(string filename)

ReadDataAsync(System.String, System.Action)

Interprets the specified data file asynchronously, interpreting it as a model or a script file. The file is interpreted as data. As a side effect, it invalidates all entities (as the file can contain arbitrary commands); the lists of entities will be re-populated lazily (at first access)

Arguments: filename (System.String) – Path to the file (Relative to the current working directory or absolute) cb (System.Action) – Callback to be executed when the file has been interpreted
public void ReadDataAsync(string filename, Action cb)

ReadTable(System.String)

Read the table corresponding to the specified name, equivalent to the AMPL statement:

Arguments: tableName (System.String) – Name of the table to be read
public void ReadTable(string tableName)

Reset()

Clears all entities in the underlying AMPL interpreter, clears all maps and invalidates all entities

public void Reset()

SetData(ampl.DataFrame, System.String)

Assign the data in the dataframe to the AMPL entities with the names corresponding to the column names.If setName is null, only the parameters value will be assigned.

Arguments: df (ampl.DataFrame) – The dataframe containing the data to be assigned setName (System.String) – The name of the set to which the indices values of the DataFrame are to be assigned.
public void SetData(DataFrame df, string setName = null)

SetOption(System.String, System.Boolean)

Set an AMPL option to a specified boolean value. In AMPL, boolean options are represented as integer: 0 for false, 1 for true.

Arguments: name (System.String) – Name of the option to be set (alphanumeric without spaces) value (System.Boolean) – Value the option must be set to
public void SetOption(string name, bool value)

SetOption(System.String, System.Double)

Set an AMPL option to a specified double value.

Arguments: name (System.String) – Name of the option to be set (alphanumeric without spaces) value (System.Double) – Value the option must be set to
public void SetOption(string name, double value)

SetOption(System.String, System.Int32)

Set an AMPL option to a specified integer value.

Arguments: name (System.String) – Name of the option to be set (alphanumeric without spaces) value (System.Int32) – Value the option must be set to
public void SetOption(string name, int value)

SetOption(System.String, System.String)

Set an AMPL option to a specified value.

Arguments: name (System.String) – Name of the option to be set (alphanumeric without spaces) value (System.String) – String representing the value the option must be set to
public void SetOption(string name, string value)

Show(ampl.Entities.Entity[])
public void Show(params Entity[] entities)

Solve()

Solve the current model

public void Solve()

SolveAsync(System.Action)

Solve the current model asynchronously

Arguments: cb (System.Action) – Call back to be executed when completed
public void SolveAsync(Action cb)

ToString()

Get a string describing the object. Returns the version of the API and either the version of the interpreter or the message “AMPL is not running” if the interpreter is not running (e.g. due to unexpected internal error or to a call AMPL.Close())

Return type: System.String
public override string ToString()


## Events¶

Error()

Raised for each AMPL error, if ampl.AMPL.EnableErrorAndWarningRouting has been called on the current object instance

Return type: System.Action{AMPLException}
public event Action<AMPLException> Error

Output()

Raised for each AMPL output, if ampl.AMPL.EnableOutputRouting has been called on the current object instance

Return type: System.Action{Kind, System.String}
public event Action<Kind, string> Output

Warning()

Raised for each AMPL warning, if ampl.AMPL.EnableErrorAndWarningRouting has been called on the current object instance

Return type: System.Action{AMPLException}
public event Action<AMPLException> Warning