Question

As mentioned earlier, vpi_load_init() allows the tool implementing the reader to load objects in a fashion that is invisible to the user. Optionally, if the user chooses to do their own loading at some point in time, then once the object handle is obtained they can use the VPI data load routine vpi_load() with the object’s vpiHandle to load the data for the specific object onto memory. Alternatively, for efficiency considerations, vpi_load() can be called with a design object collection handle of type vpiObjCollection. The collection must have already been created with vpi_create() and the (additional) selected object handles added to the load collection using vpi_create() with the created collection list passed as argument. The object(s) data is not accessible as of yet to the user’s read queries; a traverse handle must still be created. This is presented in Section 30.8.4.

Note that loading the object means loading the object from a database into memory, or marking it for active use if it is already in the memory hierarchy. Object loading is the portion that tool implementers need to look at for efficiency considerations. Reading the data of an object, if loaded in memory, is a simple consequence of the load initialization (vpi_load_init()) and/or vpi_load() optionally called by the user. The API does not specify here any memory hierarchy or caching strategy that governs the access (load or read) speed. It is left up to tool implementation to choose the appropriate scheme. It is recommended that this happens in a fashion invisible to the user without requiring additional routine calls.

The API here provides the tool with the chance to prepare itself for data load and access with the vpi_load_init(). With this call, the tool can examine what objects the user wishes to access before the actual read access is made. The API also provides the user the ability to force loads and unloads but it is recommended to leave this to the tool unless there is a need for the user application to influence this aspect.