L17: Model-based Development t n i r p t o n o D ! C - - PowerPoint PPT Presentation

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L17: Model-based Development t n i r p t o n o D ! C - - PowerPoint PPT Presentation

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L17: Model-based Development t n i r p t o n o D ! C esar S anchez n o i t c u r t s n o c r e d Grado en Ingenier a Inform atica n U Grado en Matem aticas e Inform atica Universidad Polit

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L17: Model-based Development

Este texto se distribuye bajo los t´ erminos de la Creative Commons License

C´ esar S´ anchez

Grado en Ingenier´ ıa Inform´ atica Grado en Matem´ aticas e Inform´ atica Universidad Polit´ ecnica de Madrid Wed, 15-April-2015

U n d e r c

  • n

s t r u c t i

  • n

! D

  • n
  • t

p r i n t

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HW7

Homework: HW1: Creaci´

  • n de threads en Java

HW2: Provocar una condici´

  • n de carrera

HW3: Garanatizar la exclusi´

  • n mutua con espera activa

HW4: Garantizar la exlusi´

  • n mutua con sem´

aforos HW5: Almac´ en de un dato con sem´ aforos HW6: Almac´ en de varios datos con sem´ aforos HW7: Especificaci´

  • n de un recurso compartido

HW8: Multibuffer con m´ etodos synchronized Fecha de Cierre: Viernes 17-Abril-2015 11:00am Entrega online: http://lml.ls.fi.upm.es/~entrega

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HW7: Multibuffer con m´ etodos synchronized

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HW7: Multibuffer con m´ etodos synchronized

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HW7: Multibuffer con m´ etodos synchronized

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Model-Based Development

Requirements

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Model-Based Development

Requirements Concurrent Interaction Model Formal, precise

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Model-Based Development

Requirements Concurrent Interaction Model Formal, precise 2 activities Simulation Testing yes no fix

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Model-Based Development

Requirements Concurrent Interaction Model Formal, precise 2 activities Simulation Testing yes no fix Code Generation recurso.java

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Model-Based Development

Model Simulation Testing yes no fix Code Generation recurso.java

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Model-Based Development

Model Simulation Testing yes no fix Code Generation recurso.java

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Model-Based Development

Model Simulation Testing yes no fix Code Generation recurso.java automatic systematic synchronized methods monitors message passing

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Model-Based Development

Model Simulation Testing yes no fix Code Generation recurso.java automatic systematic synchronized methods monitors message passing Today: synchronized methods

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Java synchronized Methods

public class SynchronizedCounter { private int c = 0; public synchronized void increment() { c++; } public synchronized void decrement() { c--; } public synchronized int value() { return c; } }

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Java synchronized Methods

public class SynchronizedCounter { private int c = 0; public synchronized void increment() { c++; } public synchronized void decrement() { c--; } public synchronized int value() { return c; } }

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Java synchronized Methods

public class SynchronizedCounter { private int c = 0; public synchronized void increment() { c++; } public synchronized void decrement() { c--; } public synchronized int value() { return c; } }

Synchronized methods run in mutual exclusion Only conditional synchronization needs to be programed

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Java wait and NotifyAll

Each object has a wait-set in which threads can block and queue. To block in a wait-set, a thread must invoke wait(); To wake-up one thread from the wait-set, the thread that has the synchronized lock must run: notify(); To wake-up all threads from the wait-set, the thread that has the synchronized lock must run: notifyAll();

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Synchronized Methods

example: shared counter

incr1 incr2 incr3 decr1 decr2 decr3 cont contador inc dec

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Synchronized Methods

example: shared counter

incr1 incr2 incr3 decr1 decr2 decr3 cont contador inc dec

class ContadorSync { int cont; public ContadorSync (int n) { this.cont = n; } public synchronized int getValue() { return this.cont; } public synchronized void inc () { this.cont++; } public synchronized void dec () { this.cont--; } }

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Synchronized Methods

cont contador dec inc

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Synchronized Methods

incr1 incr2 incr3 decr1 decr3 decr2 cont contador dec inc

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Synchronized Methods

cont contador dec inc decr1 synchronize queue incr2 decr3 decr2 incr1 incr3

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Synchronized Methods

cont contador dec inc incr1 incr3 decr2 decr1 incr2 decr3 synchronize queue

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Synchronized Methods

cont contador dec inc incr1 incr3 decr2 decr1 decr3 incr2

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Synchronized Methods

incr1 incr2 incr3 decr1 decr3 decr2 cont contador dec inc

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Synchronized Methods

incr1 incr2 incr3 decr1 decr3 decr2 cont contador dec inc

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Conditional Synchronization

hayDato? Almacen1 get put(x) d

prod1 prod2 prod3 cons1 cons2 cons3

example: producer consumer

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Conditional Synchronization

hayDato? Almacen1 get put(x) d

prod1 prod2 prod3 cons1 cons2 cons3

example: producer consumer = F alm(7) alm(2)

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Conditional Synchronization

hayDato? Almacen1 get put(x) d example: producer consumer

prod2 cons1 cons2 cons3

prod1 prod3

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Conditional Synchronization

hayDato? Almacen1 get put(x) d example: producer consumer

prod2 cons1 cons2 cons3

prod1 prod3

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Conditional Synchronization

hayDato? Almacen1 get put(x) d example: producer consumer cons1

prod2 cons2 cons3

prod1 prod3

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Conditional Synchronization

hayDato? Almacen1 get put(x) d example: producer consumer

prod2 cons2 cons3

prod3 cons1

prod1

= T = 7

CPRE for prod3 is false! prod2 prod1

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Conditional Synchronization

hayDato? Almacen1 get put(x) d example: producer consumer

prod2 prod1 prod2 prod1 cons2 cons3

= T = 7 prod3 cons1

wait-set

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Conditional Synchronization

hayDato? Almacen1 get put(x) d example: producer consumer

prod2 prod1 prod2 prod1 cons2 cons3

prod3

wait-set

= T = 7 cons1

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Conditional Synchronization

hayDato? Almacen1 get put(x) d example: producer consumer

cons2 cons3 cons1

prod3

wait-set prod2 prod1 prod2 prod1 recheck CPRE

= F

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Conditional Synchronization

hayDato? Almacen1 get put(x) d example: producer consumer

prod2 prod1 prod2 prod1 cons2 cons3 cons1

prod3 = F

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Conditional Synchronization

hayDato? Almacen1 get put(x) d example: producer consumer prod3

prod2 prod1 prod2 prod1 cons2 cons3 cons1

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Conditional Synchronization

hayDato? Almacen1 get put(x) d

prod1 prod2 prod3 cons1 cons2 cons3

example: producer consumer = T = 3

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Conditional Syncrhonization

synchronized public get(int n) { // CPRE : nDatos > 0 while ( ) { try { wait(); } catch (InterruptedException e) {} }

IDEA: check (at the beginning of a synchronized method) the CPRE.

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Conditional Syncrhonization

synchronized public get(int n) { // CPRE : nDatos > 0 while ( ) { try { wait(); } catch (InterruptedException e) {} }

IDEA: check (at the beginning of a synchronized method) the CPRE. Q: what to put here?

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Conditional Syncrhonization

IDEA: check (at the beginning of a synchronized method) the CPRE.

synchronized public get(int n) { // CPRE : nDatos > 0 while (nDatos <= 0) { try { wait(); } catch (InterruptedException e) {} }

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Conditional Syncrhonization

IDEA: check (at the beginning of a synchronized method) the CPRE.

synchronized public get(int n) { // CPRE : nDatos > 0 while (nDatos <= 0) { try { wait(); } catch (InterruptedException e) {} }

Q: why while and not if?

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Conditional Syncrhonization

IDEA: check (at the beginning of a synchronized method) the CPRE.

synchronized public get(int n) { // CPRE : nDatos > 0 while (nDatos <= 0) { try { wait(); } catch (InterruptedException e) {} }

Q: When and how does blocked thread awake to recheck its CPRE?

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Conditional Syncrhonization

IDEA: check (at the beginning of a synchronized method) the CPRE.

synchronized public get(int n) { // CPRE : nDatos > 0 while (nDatos <= 0) { try { wait(); } catch (InterruptedException e) {} } // // body of the work here // notifyAll(); }

Q: When and how does blocked thread awake to recheck its CPRE?

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Conditional Syncrhonization

IDEA: check (at the beginning of a synchronized method) the CPRE.

synchronized public get(int n) { // CPRE : nDatos > 0 while (nDatos <= 0) { try { wait(); } catch (InterruptedException e) {} } // // body of the work here // notifyAll(); }

wait() releases the synchronize lock. . . . and reacquires the synchronize lock right after being scheduled.

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Systematic Development

Steps:

  • 1. Map CTAD Domain to Java types
  • 2. Implement Initial condition in constructor
  • 3. Make methods synchronize (guarantees mutex)
  • 4. Use pattern for implementing CPRE:

while (~CPRE) { wait(); }

  • 5. Use notifyAll() upon exit.