During the execution of a procedure in your model, the AIMMS thread will block. This effectively prevents you from interrupting the AIMMS execution, for instance, to update data in the model, or just to abort the current procedure execution. Likewise, while a function in your DLL that was executed from within an AIMMS procedure is still running, AIMMS cannot service any end-user requests. The functions listed in this section allow your DLL and AIMMS to work together in a cooperative manner in such situations.

Handling interrupts

You can use the functions listed in this table to handle two-way interrupts.

Table 86 AIMMS API functions for handling interrupts

int AimmsInterruptCallbackInstall(AimmsInterruptCallback cb)

int AimmsInterruptPending(void)

Installing a callback

With the function AimmsInterruptCallbackInstall you can pass a function pointer with a prescribed prototype to AIMMS, which AIMMS will call on a regular basis during subsequent execution of an AIMMS procedure. Note that the installed callback is thread-local, i.e., AIMMS will only call the callback procedure from within an AIMMS procedure that is executing in the same thread in which you called AimmsInterruptCallbackInstall to install the callback.

Within a callback

Within a callback function AIMMS allows you to request or modify model data, or to run model procedures, which would normally be prohibited because calls to the AIMMS API block when AIMMS is executing (see also Thread Synchronization). Through the argument of the callback function AIMMS passes its current state (just executing, or within a solve), while you can indicate, through the return value of the callback function, whether you

  • want to interrupt the current solve but continue the remainder of the current execution,

  • want to interrupt the current execution all together, or

  • do not want to interrupt the current execution at all.

Because AIMMS will call a callback procedure quite regularly, it is advisory to keep the actions executed within it to a minimum, or AIMMS could be slowed down unacceptably.

Uninstalling the callback

You can uninstall a previously installed callback function by simply calling the function AimmsInterruptCallbackInstall with a null pointer as the callback function argument. Note that it is even possible to uninstall a callback function-or modify a callback function-during a call (by AIMMS) to the currently installed callback function.

Pending interrupts

When AIMMS calls a function within an external DLL, this would normally prevent AIMMS from servicing end-user requests to update end-user pages, modify model data, or even to interrupt the execution of the current AIMMS execution, i.e. the execution of your function. This is not a problem when a call to your function only takes a small amount of time to execute, but might be unacceptable when your function takes a long time to complete. In such situations, you might consider to insert calls to the function AimmsInterruptPending at strategic places in your source code. With it, you allow AIMMS to service such requests, and to call any callback functions installed by other DLLs. On return, AimmsInterruptPending returns

  • AIMMSAPI_TRUE when AIMMS received a request to interrupt the current execution, or

  • AIMMSAPI_FALSE when there was no interrupt request.

When an interrupt was requested you should abort the execution of your external function as soon as possible.