1 / 14

Review

Review. DEVS Formalism. Discrete-Event formalism: time advances using a continuous time base. Basic models that can be coupled to build complex simulations. Abstract simulation mechanism. DEVS atomic models semantics. y (3). x (5). s ’ = d ext ( s,e,x) (6). l ( s ) (2). s.

edana
Download Presentation

Review

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Review

  2. DEVS Formalism • Discrete-Event formalism: time advances using a continuous time base. • Basic models that can be coupled to build complex simulations. • Abstract simulation mechanism

  3. DEVS atomic models semantics y (3) x (5) s’ = d ext (s,e,x) (6) l (s) (2) s s’ = d int (s) (4) ta(s) (1) DEVS = < X, S, Y, dint , dext , ta, l >

  4. Dynamic behavior of DEVS models in M out event x1 y1 x2 t S s2=ext((s0,e),x1) s2 s1=int(x2) s1 s0 t e ta(s2) ta(s1) ta(s0) t

  5. Atomic model example: Processing Server

  6. Coupled models Structural models (multicomponent)

  7. Hierarchical vs. Incremental modelling G+B+P B+P G P B GEN-BUF-PROC BUF-PROC out in out in out out GEN BUF PROC done A B C Incremental : A andB: connect ABC BC • Petri Net : incremental • DEVS : hierarchical A B C Hierarchical : A and BC: connect

  8. Coupled models formal specification CM = < X, Y, D, {Mi}, IC, EIC, EOC, select > • Xis the set of input events; • Y is the set of output events; • D is an index for the components of the coupled model, and • " i Î D, Mi is a basic DEVS model (that is, an atomic or coupled model), defined by Mi = < Ii, Xi, Si, Yi, dinti, dexti, tai > • IC is the set of Input Couplings; • EIC is the set of External Input Couplings; • EOC is the set of External Output Couplings; • Finally, select is the tie-breaking selector.

  9. Closure Under Coupling DEVS <X, S, Y, dint,dext, dcon,ta,l > DN <X, Y, D, {Mi }, {Ii },{Zi,j }> Every DEVS coupled model has a DEVS Basic equivalent DEVS <X, S, Y, dint,dext, dcon,ta,l >

  10. Input/output ports concepts start start generator (genr) out repair shop stop repaired faulty sent transducer (transd) report out finished • Components (D) • couplings • Internal Couplings (IC) • External Input Couplings (EIC) • External Output Couplings (EOC)

  11. Coupled DEVS example < GEN-BUF-PROC model > out in out in out out GEN BUF PROC done • GEN-BUF-PROC = < X, Y, {GEN, BUF, PROC}, EIC, EOC, IC, SELECT > • X =  • Y = { out } • EIC =  • EOC = { (PROC.out, GEN_BUF_PROC.out) } • IC = { (GEN.out, BUF.in), (BUF.out, PROC.in), (PROC.out, BUF.done)} • SELECT : ({GEN, BUF, PROC}) = GEN ({BUF, PROC}) = BUF :

  12. Concept of Scheduling and Tie-break • Internal transition • Model knows its schedule time (by time advance) • External transition • Model doesn’t know its schedule time  influencer’s schedule • Conflict case • Internal and external events • External events M2 : M1’s influencee M1 : M2’s influencer M1 M2

  13. Tie-Breaking example out in GEN BUFFER PROC out in out done • * PROC = < S, X, Y, int ,ext , , ta > •  X ={in} •  Y = {out} •  S = { B, F } •  int: int(B) = F •  ext : ext(F, in) = B •  (B) = out •  ta(B) = PROCESS_TIME • * GEN = < S, X, Y, int ,ext , , ta > •  X =  •  Y = {out} •  S = {G} •  int: int(G) = G •  ext :unavailable •  (G) = out •  ta(G) = GEN_TIME (in,e) BUF (coupled model) B F (out, ta(G)) (out, ta(B)) G < PROC model > < GEN model > BUFFER: Exercise

  14. Tie-breaking • conflict schedule is resolved by assigning priority between models that cause schedules. • Internal and external events • External events • Sel : 2{Mi} {Mi} out(BUF) in(GEN) n,F Priority(BUF,GEN) = GEN done(PROC) In(GEN) n,B Priority(PROC,GEN) = GEN

More Related