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6.4. Comparing Implementation Size
cisely track all read and write operations of object fields and globals. Consequently,
this implementation includes the necessary AST transformations and
compiler adaptations.
OMOP-based Implementation The implementation of LRSTM based on the
OMOP customizes the relevant intercession handlers on the domain object to
track all state access. Lst. 6.5 in Sec. 6.2.2 shows the simplified STM domain
definition. Even though the implementation approaches are different, both
implementations have the same features and guarantees. Thus, the ad hoc
and the OMOP-based implementation are functionally equivalent.
General Comparison Note that comparing the ad hoc LRSTM implementation
and the one based on the OMOP is not necessarily fair, since this comparison
does not consider the complexity of realizing the OMOP itself. Sec. 7.1
discusses an AST-transformation-based implementation of the OMOP. Since
both AST-transformation-based implementations are very similar, this evaluation
also compares them to give a better impression of how the implementation
sizes differ between the ad hoc and the OMOP-based implementation.
Direct comparison of the ad hoc and OMOP-based LRSTM implementation
demonstrates the expected benefit of relying on the underlying abstraction.
The ad hoc implementation consists of 8 classes and 148 methods, which
account for 990 LOC and 2688 bytecodes. The OMOP-based implementation
consists of 7 classes and 71 methods, which accounts for 262 LOC and 619
bytecodes. Thus, it is roughly a quarter the size of the ad hoc implementation.
However, these results are to be expected because the ad hoc implementation
needs to replicate the same functionality the OMOP offers for managed
state and managed execution of primitives.
Detailed Comparision Tab. 6.5 details the code size of the different parts of
the LRSTM implementation to paint a more detailed picture of the size of the
involved components. While these numbers indicate a significant benefit for
the OMOP-based implementation, the detailed numbers point out a number
of differences.
The STM core routines implement the basic STM functionality and data
structures. For the OMOP-based implementation, this includes the STM domain
class, which implements state access tracking. The STM domain class
accounts for a significant part of the additional methods. Besides minor adaptations,
the remaining core routines remain unchanged.
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