abstract models of noc-based mpsocs for design space exploration
abstract models of noc-based mpsocs for design space exploration
abstract models of noc-based mpsocs for design space exploration
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2. ABSTRACT SYSTEM MODELING AND ACTOR ORIENTATION<br />
High!level!<strong>abstract</strong>ion!modeling!<strong>of</strong>!NoCS<strong>based</strong>!MPSoCs!is!an!emerging!approach!to!handle!<br />
the!vast!<strong>design</strong>!<strong>space</strong>!alternatives!<strong>of</strong>!such!systems.!However,!the!terminology!and!some!concepts!<br />
are!not!well!established.!The!following!Sections!present!the!terminology!that!is!used!in!this!Thesis,!<br />
as!well!as!define!the!basic!concepts!and!features!related!to!<strong>abstract</strong>!system!modeling!and!actor!<br />
orientation.!<br />
2.1 Terminology and Based Concepts<br />
SystemSlevel! modeling! has! been! used! to! increase! the! <strong>design</strong>! productivity! <strong>of</strong>! NoCS<strong>based</strong>!<br />
MPSoCs.!In!this!context,!modeling!and!simulation!at!high!<strong>abstract</strong>ion!levels!are!used!to!increase!<br />
and! to! simplify! the! development! and! the! validation! <strong>of</strong>! NoCS<strong>based</strong>! MPSoC,! since! not! suitable!<br />
alternative! <strong>design</strong>s! can! be! disqualified! (<strong>design</strong>! <strong>space</strong>! reduction)! in! a! shorter! time!<br />
[CAI04][JAN04][KOO08].!!<br />
According!to!Mohanty!e.t!al.![MOH02],!<strong>design</strong>!<strong>space</strong>!<strong>exploration</strong>!is!the!process!<strong>of</strong>!analyzing!<br />
several! implementation! alternatives! to! identify! an! optimal! solution.! Such! alternatives! are! not!<br />
identical!but!they!have!to!per<strong>for</strong>m!the!same!functions!and!to!provide!the!same!utility.!As!defined!<br />
in! [KIE99],! the! <strong>design</strong>! <strong>space</strong>! <strong>exploration</strong>! is! a! tradeS<strong>of</strong>f! between! three! issues:! modeling! ef<strong>for</strong>t,!<br />
evaluation!speed,!and!accuracy!<strong>of</strong>!the!obtained!results!when!compared!with!a!reference!model.!<br />
Figure! 3! (a)! illustrates! the! <strong>abstract</strong>ion! pyramid! that! represents! the! three! issues! in! per<strong>for</strong>mance!<br />
modeling 8 ,! which! are! organized! in! different! <strong>abstract</strong>ion! levels! according! to! the! modeling! and!<br />
evaluation!cost.!The!high!level!modeling!activity!is!a!tradeS<strong>of</strong>f!between!level/<strong>of</strong>/details!and!model/<br />
confidence! [BRO96].! The! level! <strong>of</strong>! detail! refers! to! the! structural! and! behavior! <strong>abstract</strong>ion! <strong>of</strong>! the!<br />
system!components.!The!structural!<strong>abstract</strong>ion!means!the!granularity!<strong>of</strong>!a!data!storage!and!the!<br />
number!<strong>of</strong>!included!components!and!their!interconnects.!The!behavioral!<strong>abstract</strong>ion!includes!how!<br />
and! when! the! components! update! their! internal! state! and! concurrently! interact! with! other!<br />
components!(e.g.!how!the!memory!is!accessed!by!a!processor).!The!model!confidence!means!how!<br />
useful!the!model!is!<strong>for</strong>!a!particular!purpose!<strong>for</strong>!instance!in!terms!<strong>of</strong>!accuracy!when!compared!to!a!<br />
reference!model.!!<br />
Figure! 3! (b)! places! the! proposed! approach! (which! is! detailed! in! Chapter! 4! and! 5! <strong>of</strong>! this!<br />
Thesis),! according! to! the! pyramid! internal! structure.! As! shown! in! Figure! 3! (b),! the! proposed!<br />
approach! allows! flexible! modeling,! by! employing! accurate! and! <strong>abstract</strong>! executable! <strong>models</strong>! that!<br />
can! be! used! to! <strong>design</strong>! <strong>space</strong>! <strong>exploration</strong>! <strong>of</strong>! NoCS<strong>based</strong>! MPSoCs! be<strong>for</strong>e! it! goes! down! to! the! RTL!<br />
execution!(HEMPS),!which!is!then!used!to!identify!the!optimal!<strong>design</strong>!solution.!It!should!be!clear!<br />
that! <strong>design</strong>! <strong>space</strong>! <strong>exploration</strong>! discussed! in! this! Thesis! is! not! restricted! to! the! architecture!<br />
8!! A!detailed!description!<strong>of</strong>!each!issue!in!per<strong>for</strong>mance!modeling!can!be!found!in![KIE99].!!<br />
!<br />
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