Hierarchy flattening

Finally, circuits constructed in the structural style have components and therefore an explicit hierarchy. Flattening the hierarchy during optimization resulted in a circuit that was always smaller than when the hierarchy was preserved and only the components optimized. 

I am a Service Manager within the Social Services Department of a London borough. The Service Manager role is a combination of several middle management functions in an attempt to flatten the hierarchy and we are stretched in many directions. It is not uncommon to be representing the local authority at the highest level one moment, then be locked into complex local operational concerns the next. 

The minimal, and in some cases negative, impact of research on inclusion on its subjects has often been reflected in the research relations themselves and the way in which they operate within, and perpetuate, uneven power structures. Addressing these imbalances of power and ensuring that research practices themselves are inclusive is vital and requires a high level of sensitivity to issues of power. Research ethics protocols, concerned with ensuring that no harm is done to research subjects, do not require this level of sensitivity, but researchers need to interrogate the way in which their research positions their research subjects and to find ways of flattening the hierarchy between the researcher and the researched. 

You have boolean optimization turned on. Again, this is appropriate only for random logic. If you do have random logic in your design, consider grouping it into a separate level of hierarchy and compile it separately with the flatten or boolean structuring switch turned on. 

The structural style architecture lends itself to a demonstration of the differing effects of optimizing a circuit by flattening or preserving its hierarchy. These techniques were discussed in section 2.4. The circuit statistics... 

This dicuit has three levels in its hierarchy two of which are associated with the component. These two can be reduced to one widiout any major effect on the circuit as the process block is die only element widiin Ae component. Hence, the important structure of the design is stUl preserved if the component itself is flattened. 

The two optimization processes demonstrated that flattening or preserving the hierarchy can produce similar results but this is circuit dependent, as will be shown in later examples. Employing a low level of effort generally provides the best trade-off between QPU time during optimization and circuit area. 

Figure 5.18 Optimized circuit for the STRING SSIGN, AGGREGATE and SYNC WAIT architectures. Each two-level hierarchy has been flattened.

Figure 5.19 Optimized circuit (with flattened hierarchy) for the ASYNCJFI architecture.

Figure 5.23 Optimized DFF architecture with a flattened hierarchy.

Figure 5J26 Optimized REG GEN and IRREG GEN architectures with flattened hierarchy. 

The BCD to seven-segment display converter designed in the previous chapter was optimized in two ways. One involved the global optimization of the circuit and the flattening of its component hierarchy. The other preserved the hierarchy and optimized individual components. There was shown to be littie to choose between either approach. 

The hierarchy in a description that is created by a Block statement will usually be flattened by the synthesizer. An attribute such as Merge can often be used to preserve this hierarchy (Box 7,6). 

Figure 7.10 shows the next level of the hierarchy below the decoder block. This contains the two blocks that represent this block s Process statements. The statistics for the s)mfhesized circuit contained in all four of these processes are shown in Table 7.1. As the Block statement has been flattened by the S5mthesizer, the two processes in the SEQUENCE-BEHAVIOUR entity-architecture were originally contained in the Enabler block. The circuits associated with these statistics are not shown. As can be observed, the proc-... 

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.

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. 

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