Calling hierarchy

The set of commands and actions that follow a sequence of priority to reach a conclusion is called hierarchy. Hierarchy identifies the actions to be considered in an order of effectiveness to resolve hazard and risk situations. It helps in locating a problem of risk, its analysis and approaches to avoid this risk, a plan for action, and its effects on productivity. 

The Higgs mass, on the other hand, is completely arbitrary within the paradigm of the SM. In fact, there are arguments suggesting that the SM with fundamental Higgs fields cannot be the full story and that some new kind of physics must appear at a high energy scale. This is linked to the so-called hierarchy problem and will be briefly mentioned in the next section. 

If A 10 -10 GeV/c, the problem arises of explaining the presence of two such enormously different energy scales in the theory the so-called hierarchy problem. For a very pedagogical introduction, see Altarelli... 

Selective in-line expansion of model calls, where a call to a model is replaced by the functionality of the called model. Once expanded, the optimization algorithms can be applied across the call hierarchy. 

Local port - In contrast, a local port transfers data across the calling hierarchy only. They serve as values that are passed in and out of procedure and function calls, and are valid only at the call boundary. 

The calling hierarchy of the input description can be modified by the designer using user-driven behavioral transformations. These transformations include inline expansion of model calls and mcqtping of operators to models. 

Behavioral transformations identify the parallelism in the HardwareC description using compiler optimization techniques. They also permit the designer to change the procedure calling hierarchy to conux)l the granularity of hardware sharing in subsequent synthesis steps. The BIF is used as the underlying representation for all transformations. 

Figure 4.1 Example of the calling hierarchy for model A. Model A calls models 5i and B2, and model B calls model C,...

In this section, we further separate the sequencing graph hierarchy into two forms calling hierarchy and control-flow hierarchy. 

Calling hierarchy Calling hierarchy refers to the nesting structure of procedure and function calls in the model. Consider for example four... 

Figure 5.1 Resource sharing across the call hierarchy (a) model Z cannot be shared among models X and Y, (b) after flattening, model Z can be shared among the two invocations in model A.

Synthesis across the hierarchy. As described in Chapter 4, the sequencing graph model supports two forms of hierarchy calling hierarchy, which refos to the nesting structure of model call vertices, and control-flow hierarchy, which refers to the nesting structure of conditionals and loops. 

In-line expand model calls. A model may consist of a hierarchy of calls to other models in the system. For example, an 8-bit adder may call two 4-bit adders cascaded in series. The designer can optionally and selectively replace a model call by its description. By flattening the calling hierarchy, optimization can be performed across the model boundaries. 

For each instance entry, Hercules can generates a corresponding SIF model. Therefore, an instance can be mapped to one or mwe SIF models, with each SIF model corresponding to a particular configuration of usa-driven behavi< al transformations that was performed on the model. For example, consider a procedure Main that calls a function Func. If the calling hierarchy is unchanged, then a default SIF model is created. If the call to Func is in-line expanded, then the resulting SIF model would be different. 

At the system level, the designer reads in one or more SIF models. For each model that is read in, all models in its calling hierarchy are also recursively read in. Hebe automatically retrieves the design points that were previously synthesized for a given model. The area and delay costs are extracted from these design points and made available in the current synthesis session. 

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