Spatial Programming Spatial Programming using Smart Messages: using Smart Messages:

Design and Design and ImplementationImplementation

Cristian BorceaCristian Borcea, Chalermek , Chalermek Intanagonwiwat, Porlin Kang, Ulrich Intanagonwiwat, Porlin Kang, Ulrich

Kremer, and Liviu IftodeKremer, and Liviu IftodeDepartment of Computer ScienceDepartment of Computer Science

Rutgers UniversityRutgers University

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Distributed object Distributed object tracking over a largetracking over a large

geographical areageographical area

Cars collaborating Cars collaborating for a safer and for a safer and

more fluid trafficmore fluid traffic

Computers Go Outdoors, Computers Go Outdoors, Embedded Everywhere in the Embedded Everywhere in the

Physical WorldPhysical World

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Traditional (Indoor) Traditional (Indoor) Distributed ComputingDistributed Computing

Computation is distributed for performance or Computation is distributed for performance or fault tolerance fault tolerance

Relatively easy to programRelatively easy to program– Nodes are computationally equivalentNodes are computationally equivalent

– Networking is robust and has acceptable delaysNetworking is robust and has acceptable delays

– Configuration is stableConfiguration is stable

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Outdoor Distributed ComputingOutdoor Distributed Computing

Computation is physically distributedComputation is physically distributed

– Nodes distributed across the physical spaceNodes distributed across the physical space

– Location-aware computingLocation-aware computing

Hard to programHard to program

– Nodes are functionally heterogeneous and Nodes are functionally heterogeneous and

potentially mobilepotentially mobile

– Ad hoc wireless networks of embedded systemsAd hoc wireless networks of embedded systems

– Volatile configurationsVolatile configurations

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ExampleExample

Mobile sprinkler Mobile sprinkler with temperature with temperature sensorsensor

Left HillLeft Hill Right HillRight Hill

Hot spotHot spot

““Water the hottest spot on the Left Hill”Water the hottest spot on the Left Hill” Number and location of mobile sprinklers Number and location of mobile sprinklers

are unknownare unknown Configuration is not stable over timeConfiguration is not stable over time

– Sprinklers moveSprinklers move

– Temperature changesTemperature changes

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Traditional Distributed Traditional Distributed Computing Computing

Does Not Work Well OutdoorsDoes Not Work Well Outdoors End-to-end data transfers may hardly completeEnd-to-end data transfers may hardly complete Fixed address naming and routing (e.g., IP) are Fixed address naming and routing (e.g., IP) are

too rigidtoo rigid Difficult to deploy new applications in existing Difficult to deploy new applications in existing

networksnetworks Outdoor distributed computing requires novel Outdoor distributed computing requires novel

abstractions and programming modelsabstractions and programming models– How to write outdoor distributed applications?How to write outdoor distributed applications?

– How to deploy new applications in existing networks?How to deploy new applications in existing networks?

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OutlineOutline

MotivationMotivation Spatial Programming (SP) ModelSpatial Programming (SP) Model SP Implementation using Smart MessagesSP Implementation using Smart Messages SP ApplicationSP Application ConclusionsConclusions

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Traditional (Indoor) ProgrammingTraditional (Indoor) Programming

Programs access data through variablesPrograms access data through variables Variables mapped to physical memory locationsVariables mapped to physical memory locations Page Table and OS guarantee reference Page Table and OS guarantee reference

consistency consistency Access time has an (acceptable) upper boundAccess time has an (acceptable) upper bound

ProgramProgram

Virtual Address SpaceVirtual Address Space

Page Table + OSPage Table + OS

Physical Memory

Variable accessVariable access

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From Indoor to Outdoor From Indoor to Outdoor ComputingComputing

Virtual Address SpaceVirtual Address Space Space RegionSpace Region

VariablesVariables Spatial ReferencesSpatial References

Variables mapped to Variables mapped to physical memoryphysical memory

Spatial references mappedSpatial references mappedto systems embedded in to systems embedded in the physical spacethe physical space

Reference consistencyReference consistency

Bounded access timeBounded access time

??

??

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Spatial Programming (SP) at a Spatial Programming (SP) at a GlanceGlance

Provides a Provides a virtual name spacevirtual name space over outdoor over outdoor

networks of embedded systemsnetworks of embedded systems

Embedded systems named by their locations and Embedded systems named by their locations and

propertiesproperties

Runtime system takes care of name resolution, Runtime system takes care of name resolution,

reference consistency, and networking aspectsreference consistency, and networking aspects

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radiusradius

Hill = new Space({lat, long}, radius);Hill = new Space({lat, long}, radius);

{lat,long}{lat,long}

Space RegionsSpace Regions

Virtual representation of a physical spaceVirtual representation of a physical space Similar to a virtual address space in a Similar to a virtual address space in a

conventional conventional

computer systemcomputer system Defined statically or dynamicallyDefined statically or dynamically

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Spatial ReferencesSpatial References

Defined as Defined as {space:property}{space:property} pairs pairs Virtual names for embedded systemsVirtual names for embedded systems Similar to variables in conventional programmingSimilar to variables in conventional programming

Indexes used to distinguish among similar Indexes used to distinguish among similar

systems systems

in the same space regionin the same space region

{Hill:robot[0]}{Hill:robot[0]}

{Hill:robot[1]}{Hill:robot[1]}

{Hill:motion[0]}{Hill:motion[0]}

HillHill

r2r2r7r7

m5m5

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Reference ConsistencyReference Consistency

At first access, a spatial reference is mapped to At first access, a spatial reference is mapped to

an embedded system located in the specified an embedded system located in the specified

space space Mappings maintained in per-application Mapping Mappings maintained in per-application Mapping

Table (MT) – similar to a page tableTable (MT) – similar to a page table

Subsequent accesses to the same spatial Subsequent accesses to the same spatial reference will reach the same system (using MT) reference will reach the same system (using MT) as long as it is located in the same space region as long as it is located in the same space region

{space, property, index}{space, property, index}{unique_address, location}{unique_address, location}

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Reference Consistency ExampleReference Consistency Example

Left HillLeft Hill Right HillRight Hill

{Left_Hill:robot[0]}.move = ON;{Left_Hill:robot[0]}.move = ON;

r2r2 r7r7r5r5

{Left_Hill:robot[0]}.move = OFF;{Left_Hill:robot[0]}.move = OFF;

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Space CastingSpace Casting

{Left_Hill:robot[0]}{Left_Hill:robot[0]}

Left HillLeft Hill Right HillRight Hill

{Right_Hill:(Left_Hill:robot[0])}{Right_Hill:(Left_Hill:robot[0])}

r7r7

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Bounding the Access TimeBounding the Access Time

How to bound the time to access a spatial How to bound the time to access a spatial reference?reference?– Systems may move, go out of space, or disappearSystems may move, go out of space, or disappear

Solution: associate an explicit timeout with the Solution: associate an explicit timeout with the spatial reference accessspatial reference access

try{try{ {Hill:robot[0], timeout}.{Hill:robot[0], timeout}.move = ON;move = ON;}catch(TimeoutException e){}catch(TimeoutException e){ // the programmer decides the next action// the programmer decides the next action}}

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for(i=0; i<1000; i++)for(i=0; i<1000; i++) try{try{

if (if ({Left_Hill:Hot[i], timeout}.{Left_Hill:Hot[i], timeout}.temp > Max_temp)temp > Max_temp)Max_temp = Max_temp = {Left_Hill:Hot[i], timeout}{Left_Hill:Hot[i], timeout}.temp;.temp;Max_id = i;Max_id = i;

}catch(TimeoutException e) }catch(TimeoutException e) break;break; {Left_Hill:Hot[Max_id], timeout}{Left_Hill:Hot[Max_id], timeout}.water = ON;.water = ON;

Spatial Programming Spatial Programming ExampleExample

Water the hottest spot on the Left HillWater the hottest spot on the Left Hill

Mobile sprinkler Mobile sprinkler with temperature with temperature sensorsensor

Left HillLeft Hill Right HillRight Hill

Hot spotHot spot

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OutlineOutline

MotivationMotivation Spatial Programming (SP) ModelSpatial Programming (SP) Model SP Implementation using Smart MessagesSP Implementation using Smart Messages SP ApplicationSP Application ConclusionsConclusions

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Smart Messages at a GlanceSmart Messages at a Glance Smart Message (SM)Smart Message (SM)

– User defined distributed application similar to a User defined distributed application similar to a mobile agentmobile agent

– Executes on nodes of interest named by propertiesExecutes on nodes of interest named by properties– Migrates between nodes of interest using self-Migrates between nodes of interest using self-

routingrouting Self-RoutingSelf-Routing

– Application-level routing executed at every nodeApplication-level routing executed at every node– Applications can change routing during executionApplications can change routing during execution

Cooperative NodesCooperative Nodes– Execution environment (Virtual Machine)Execution environment (Virtual Machine)– Memory addressable by names (Tag Space)Memory addressable by names (Tag Space)– Code cacheCode cache

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Smart Messages PrototypeSmart Messages Prototype

Modified version of Sun’s Java K Virtual Modified version of Sun’s Java K Virtual

MachineMachine– Small memory footprint (160KB)Small memory footprint (160KB)

SM and tag space primitives implemented SM and tag space primitives implemented

inside virtual machine as native methods inside virtual machine as native methods

(efficiency)(efficiency) Implemented I/O tags: GPS location, neighbor Implemented I/O tags: GPS location, neighbor

discovery, image capture, light sensor, discovery, image capture, light sensor,

system statussystem status

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Spatial Programming Spatial Programming Implementation Using Smart Implementation Using Smart

Messages Messages SP application translates into an SMSP application translates into an SM

– Spatial reference access translates into an SM Spatial reference access translates into an SM migration to the mapped nodemigration to the mapped node

– Embedded system properties: TagsEmbedded system properties: Tags

SM self-routes using geographical routing and SM self-routes using geographical routing and content-based routing content-based routing

Reference consistencyReference consistency− Unique addresses (stored in mapping table) are Unique addresses (stored in mapping table) are

unique tags created at nodesunique tags created at nodes

− SM carries the mapping tableSM carries the mapping table

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Max_temp = {Left_Hill:Hot[1], timeout}.temp;Max_temp = {Left_Hill:Hot[1], timeout}.temp;

SP to SM Translation: ExampleSP to SM Translation: Example

Left HillLeft Hill Right HillRight Hill

Spatial Reference AccessSpatial Reference Access

Smart MessageSmart Message

ret = migrate_geo(location, timeout);ret = migrate_geo(location, timeout);if (ret == LocationUnreachable)if (ret == LocationUnreachable) ret = migrate_tag(yU78GH5, timeout);ret = migrate_tag(yU78GH5, timeout);if ((ret == OK) && (location == Left_Hill))if ((ret == OK) && (location == Left_Hill)) return readTag(temp);return readTag(temp);else throw TimeoutException else throw TimeoutException

{Left_Hill,Hot,1}{Left_Hill,Hot,1} {yU78GH5,location}{yU78GH5,location}MappingMappingTableTable

CodeCode

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SP Application: Intrusion SP Application: Intrusion DetectionDetection

Code Size breakdown for SM Code Size breakdown for SM (Application + SP Library)(Application + SP Library)

Code Size breakdown for Code Size breakdown for SP librarySP library

Ad hoc network: HP iPAQs with 802.11 cards and GPS devicesAd hoc network: HP iPAQs with 802.11 cards and GPS devices

user nodeuser nodelight sensorlight sensorcamera nodecamera node

regular noderegular node

monitoredmonitoredspacespace

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Execution Time BreakdownExecution Time Breakdown

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ConclusionsConclusions

Spatial Programming makes outdoor Spatial Programming makes outdoor

distributed computing simpledistributed computing simple

– Volatility, mobility, configuration dynamics, ad-hoc Volatility, mobility, configuration dynamics, ad-hoc

networking are hidden from programmernetworking are hidden from programmer

Implementation on top of Smart Messages Implementation on top of Smart Messages

– Easy to deploy new applications in the networkEasy to deploy new applications in the network

– Quick adaptation to highly dynamic network Quick adaptation to highly dynamic network

configurationsconfigurations

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Thank you!Thank you!

http://discolab.rutgers.edu/sp/