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Emerald - et OO-språk for distribuerte applikasjoner

Emerald - et OO-språk for distribuerte applikasjoner. Eric Jul PSE. Immutable Objects. Immutable objects cannot change state Examples: The integer 17 User-defined immutable objects: for example complex numbers Immutable objects are omnipresent

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Emerald - et OO-språk for distribuerte applikasjoner

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  1. Emerald - et OO-språk for distribuerte applikasjoner Eric Jul PSE

  2. Immutable Objects • Immutable objects cannot change state • Examples: The integer 17 • User-defined immutable objects: for example complex numbers • Immutable objects are omnipresent • Types must be immutable to allow static type checking

  3. Types are Immutable Objects Example: arrays varai: Array.of[Integer] ai <- Array.of[Integer].create[] varaai: Array.of[Array.of[Integer]]

  4. Let’s look at the implementation of Array (Switch to code…)

  5. Why Mobility • Local callsaretypically 1,000 – 10,000 times faster thanremotecalls • Mobility for: • performance • availability • NOTE: oftentradeoff - conflicting

  6. Mobility and Location Concepts locate X returns (one of) the object X’s locations move X to Y if possible, move the object X to the node where Y is (or ratherwas) fix X at Y as move BUT MUST migrate disregardsubsequentmoves refix X at Y as fix but for fixedobjects unfix X allow normal moves

  7. var B: some data object … X.F[move B] … … X.F[visit B] … object X operation F[arg:T] loop arg.g[…] exit after many loops end loop end X Call-by-move

  8. Breakeven for Accessing a Parameter Breakeven: The number of calls to the parameter objectswhere it costsabout the same to do REMOTE access as it costs to use Call-by-Visit

  9. How Many Calls of B? Questions: given a normal PC enviroment, say 2 GHz CPU, 10 Mbit/s Ethernet, how many calls of a small (say 100 bytes) argument B before breakeven? • 1 • 10 • 100 • 1,000 • 10,000 • 100,000

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