Communicating Individual Identifier Values

Communicating identifier values

With every identifier handle AIMMS lets you retrieve all associated nondefault data values on an element-by-element basis. In addition, AIMMS lets you search whether a nondefault value exists for a particular element tuple, and make assignments to individual element tuples. this table lists all the available AIMMS API functions for this purpose.

Table 78 AIMMS API functions for sparse data communication

int AimmsValueCard(int handle, int *card)

int AimmsValueResetHandle(int handle)

int AimmsValueSearch(int handle, int *tuple, AimmsValue *value)

int AimmsValueNext(int handle, int *tuple, AimmsValue *value)

int AimmsValueNextMulti(int handle, int *n, int *tuples, AimmsValue *values)

int AimmsValueRetrieve(int handle, int *tuple, AimmsValue *value)

int AimmsValueAssign(int handle, int *tuple, AimmsValue *value)

int AimmsValueAssignMulti(int handle, int n, int *tuples, AimmsValue *values)

int AimmsValueDoubleToMapval(double value, int *mapval)

int AimmsValueMapvalToDouble(int mapval, double *value)


The function AimmsValueCard returns the cardinality of a handle, i.e. the number of nondefault elements of the associated identifier slice. You can call this function, for instance, when you need to allocate memory for the data structures in your own code before actually retrieving the data.

Retrieving nondefault values

The functions AimmsValueResetHandle, AimmsValueSearch and AimmsValueNext retrieve nondefault values associated with a handle on an element-by-element basis.

  • The function AimmsValueResetHandle resets the handle to the position just before the first nondefault element.

  • The function AimmsValueSearch expects an input tuple of element numbers (in the slice domain), and returns the first tuple for which a nondefault value exists on or following the input tuple.

  • The function AimmsValueNext returns the first nondefault element directly following the element returned by the last call to AimmsValueNext or AimmsValueSearch, or the first element if the function AimmsValueResetHandle was called last. The function fails when there is no such element.

By calling AimmsValueResetHandle and subsequently AimmsValueNext it is possible to retrieve all nondefault values. By calling the function AimmsValueSearch you can directly skip to a particular element tuple if you have found that the intermediate tuples are not interesting anymore, and continue from there.

No scalar handles

The functions AimmsValueResetHandle, AimmsValueNext and AimmsValueSearch do not accept handles to scalar (i.e. 0-dimensional) identifier slices. To retrieve and assign scalar values you should use the functions AimmsValueRetrieve and AimmsValueAssign explained below.

Unordered versus ordered retrieval

The particular element returned by the functions AimmsValueSearch and AimmsValueNext may differ depending on the setting of the ordered flag for the handle. If the handle has been created unordered (default), the values returned successively are ordered by increasing element number in a right-to- left tuple order. If the handle has been created ordered, AIMMS will return values in accordance with the ordering principles imposed on all local tuple domains.

Raw data retrieval

By default, AIMMS will only pass values for element tuples that lie within the current contents of the intersection of the call domain and declaration domain of an identifier. Thus, the values that get passed may depend on a dynamically changing domain restriction that is part of the index domain in the declaration of an identifier. When the raw modification flag is set for a handle, AIMMS will pass all available data values in the call domain, regardless of the domain restrictions.

Return tuple and value

All data retrieval functions return a tuple and the associated nondefault value. The interpretation of the value argument for all possible storage types was discussed on Passing integer, double or string values. The tuple argument must be an integer array of length equal to the slice dimension of the handle. Upon success, the tuple contains the element numbers in the global domain sets for every non-sliced dimension.

Element or ordinal numbers

By setting the flag elementsasordinals during the creation of a handle, you can modify the default tuple representation. If this flag is set, the tuples returned by AIMMS will contain ordinal numbers corresponding to the respective call domains associated with the handle. Similarly, AIMMS expects tuples that are passed to it, to contain ordinal numbers as well, when this flag is set.


While at first sight the choice for representing tuples by their element numbers in the global domain of a handle may seem less convenient than ordinal numbers in its call domain, you must be aware that the latter representation is not invariant under changes in the contents of the call domain. Alternatively to setting the flag elementsasordinals, you can also convert the returned element numbers into these formats using the AIMMS API functions discussed in Accessing Sets and Set Elements.

Value types

The expected storage type of the data values returned by the data retrieve functions can be obtained using the function AimmsAttributeStorage. The possible storage types for the various identifier types are listed below:

  • numeric parameters and variables return double or integer values,

  • all set types return binary values,

  • element parameters return integer element numbers, and

  • string and unit parameters return string values.

Element parameter values

The element numbers returned for element parameters are relative to the set handle returned by the function AimmsAttributeElementRange. You can use the AIMMS API functions of Accessing Sets and Set Elements to obtain the associated ordinal numbers or string representations.

Set values

For sets (either simple, relation or indexed), the data retrieval functions return the binary value 1 for just those elements (or element tuples) that are contained in the set. For indexed sets, AIMMS returns tuples for which the last component is the element number of an element contained in the set slice associated with all but the last tuple components.

Converting special numbers

When a handle to a numeric parameter or variable has been created with the special flag set, the data retrieval functions will pass any special number value associated with the handle as is (see also Declaration of External Procedures and Functions and Obtaining Identifier Attributes). AIMMS represents special numbers as double precision floating point numbers outside AIMMS’ ordinary range of computation. The function AimmsValueDoubleToMapval returns the MapVal value associated with any double value (see also this table), while the function AimmsValueMapvalToDouble returns the double representation associated with any type of special number.

Retrieving specific values

The function AimmsValueRetrieve returns the value for a specific element tuple in the slice domain. This value can be either the default value or a nondefault value. The tuple must consist of element numbers in the corresponding domain sets. When the raw flag is not set, the function fails (but still returns the default value of the associated identifier) for any tuple outside of the index domain of the handle. When the raw flag is set, the function fails only when there is no data for the tuple.

Assigning values

The function AimmsValueAssign lets you assign a new value to a particular element tuple in the slice domain. If you want to assign the default value you can either pass a null pointer for value, or a pointer to the appropriate default value. The function fails if you try to assign a value to an element tuple outside the contents of the call domain of the handle. When the raw flag is not set, the function will also fail if the assigned tuple lies outside of the current (active) contents of the declaration domain.

Exchanging multiple values

When a particular identifier handle requires the exchange of a large amount of values, you are strongly encouraged to use the functions AimmsValueNextMulti and AimmsValueAssignMulti instead of the functions AimmsValueNext and AimmsValueAssign. In general, AIMMS can perform the simultaneous exchange of multiple values much more efficient than the equivalent sequence of single exchanges. For both functions, the tuples array must be an integer array of length n times the slice dimension of the handle, while the values array must be the corresponding AimmsValue array of length n.

  • In the function AimmsValueNextMulti, AIMMS will fill the tuples array with the respective tuples for which nondefault values are returned in the values array. Upon return, the n argument will contain the actual number of values passed.

  • In the function AimmsValueAssignMulti, the tuples array must be filled sequentially with the respective tuples to which the assignments take place via the values array.

When your data transfer involves the addition of a large amount of set elements to an AIMMS set as well, you may also want to consider using the function AimmsSetAddElementMulti (see Accessing Sets and Set Elements).

Communicating scalar values

When a handle corresponds to a 0-dimensional (i.e. scalar) identifier slice, you can still use the AimmsValueRetrieve and AimmsValueAssign to retrieve its value or assign a value to it. In this case, the tuple argument is ignored.

Assigning set values

When you want to delete or add an existing element or element tuple to a set, you must assign the value 0 or 1 to the associated tuple respectively. If you want to add a tuple of nonexisting simple elements, you must first add these elements to the corresponding global simple domain sets using the function AimmsSetAddElement discussed below.