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Region Streams
Functional
Macroprogramming for
Sensor Networks
Ryan Newton
MIT CSAIL
[email protected]
Matt Welsh
Harvard University
[email protected]
Tracking a vehicle
Tracking many vehicles
Programming Sensornets is
HARD

Message passing is painful


Programming global behavior at the local level
Life at the node level is messy



Low level hardware and communication details
Limited node resources (cpu, memory)
Lost messages and failed nodes
Macroprogramming Vision

The programmer thinks in terms of the
whole network, manually translates into
node programs.

Can some of this translation be
automated by a tool or compiler?

An example: TinyDB



Declarative, global-level queries
No message passing or node details
Limited to certain kinds of data gathering
Compile
Down
Regiment Data Model
Regiment’s
Purpose
Provide a rich set of (fully composable)
operators
to work with data distributed over
time and space.
Forming Region
Mapping an operation
Folding a Region
Regiment Programming Model

Data Model: Sensor network data
represented as streams of tuples, one
stream per node.

Regions group streams

Map allows data parallel computation
across a region

Fold aggregates the streams in a region
Simple and Derived Regions

Simple Regions, created from geometric
or radio relationships:





K-hop-neighborhood
K-nearest nodes
All nodes within circle (square, etc)
All nodes in network (“world”)
Derived Regions, built from other
regions



Union, Intersection
Map, Filter
(Many other library procedures:
border, sparsify, cluster, etc)
Relationship to SQL queries
SELECT nodeid,light,temp
FROM sensors
WHERE light > 400
SAMPLE PERIOD 1024
let r1 = filter (\n -> read LIGHT n > 400)
world
r2 = map (\n -> (read ID n, read LIGHT n, read TEMP
n))
r1
in set_freq 1024 r2
Tracking a vehicle in Regiment
let abovethresh (p,x) = p > threshold
select node = (read PROXIMITY node,
get_location node)
in centroid (filter aboveThresh
(map select world))
Tracking a vehicle in Regiment
let abovethresh (p,x) = p > threshold
select node = (read PROXIMITY node,
get_location node)
in centroid (filter aboveThresh
(map select world))
Tracking a vehicle in Regiment
let abovethresh (p,x) = p > threshold
select node = (read PROXIMITY node,
get_location node)
in centroid (filter aboveThresh
(map select world))
Tracking a vehicle in Regiment
let abovethresh (p,x) = p > threshold
select node = (read PROXIMITY node,
get_location node)
in centroid (filter aboveThresh
(map select world))
Tracking a vehicle in Regiment
let abovethresh (p,x) = p > threshold
select node = (read PROXIMITY node,
get_location node)
in centroid (filter aboveThresh
(map select world))
Tracking a vehicle in Regiment
let abovethresh (p,x) = p > threshold
select node = (read PROXIMITY node,
get_location node)
in centroid (filter aboveThresh
(map select world))
Tracking a vehicle in Regiment
let abovethresh (p,x) = p > threshold
select node = (read PROXIMITY node,
get_location node)
in centroid (filter aboveThresh
(map select world))
Multi-target Tracking
let abovethresh (p,x) = p > threshold
select node = (read PROXIMITY node,
get_location node)
selected = filter aboveThresh
(map select world)
in centroid selected
Multi-target Tracking
let abovethresh (p,x) = p > threshold
select node = (read PROXIMITY node,
get_location node)
selected = filter aboveThresh
(map select world)
globs = cluster selected
targets = map centroid globs
in targets
Tracking with sentries
let abovethresh (p,x) = p > threshold
select node = (read PROXIMITY node,
get_location node)
selected = filter aboveThresh
(map select world)
globs = cluster selected
targets = map centroid globs
sentries = map read (border world)
event = whenAny abovethresh sentries
in until event nullArea targets
Current Compiler Status

Compiles to Token Machines




Node level state machine exposing
“tokens” for region membership
Whole program analysis on token
machines enables optimization
Token machines currently run in
simulation
Soon will compile to NesC/TinyOS
Future work, Research challenges
Finish prototype, evaluate on real motes
 Provide effective controls over stream
rates and energy usage


Can adaptive runtimes reduce energy usage
Attack specific problem domains to
uncover useful domain primitives
 Understand general global-to-local
compilation and optimization strategies


Preliminary work; would love your
feedback!
End
Ryan Newton
MIT CSAIL
[email protected]
Matt Welsh
Harvard University
[email protected]
Region Streams:
Functional Macroprogramming for Sensor Networks
With what glue?: The language

General purpose purely functional
macroprogramming language

Uses monads, Functional Reactive Programming
to encapsulate Regions/Streams safely
Has Conditionals
 Has user defined functions
 BUT: No arbitrary depth recursion


User defined procedures inline at compile time
•
•
•
Control flow is known, programs terminate
Thus Regiment has no stack/heap at runtime
But, procedures stick around in argument position
Lazy (call-by-need) semantics

Regiment is a lazy functional language; values
are computed when they’re needed.


If you only use only part of a data structure, compute
only that part.
We might not want to compute a region at all places
and times.
• Consider the intersection of contiguous regions

Don’t think of region operations as strict,
imperative commands.

Instead, they declare relationships.
Compilation Strategy

Safe ADT for Regions and Streams




Only interface through map/fold/filter
Can reason about time/space
properties of code with type system
Source level rewrite optimizations
based on algebraic properties
Program analysis to recognize
efficient communication patterns

analyze region contiguity, area,
diameter
Token Machines

Token handlers are like a functions
whose last call is cached


Can be broadcast to neighbors as well
as called locally
Each region has some place(s)
from which its formed

Formation and membership tokens
• Compiler’s place analysis
Regions are Streams of Spaces
Full Tracking Program
let abovethresh (p,x) = p > threshold
read node = (read_sensor PROXIMITY node,
get_location node)
in centroid (afilter aboveThresh
(amap read world))
centroid area = divide (afold accum (0,0) area)
accum (wsum, xsum) (w,x) = (w + wsum, x*w + xsum)
divide stream = smap (\(w,x) -> x/w) stream
Core types in Regiment
type Stream 'a ≈≈ (Time -> 'a)
type Space 'a ≈≈ (Location -> Multiset 'a)
type Event 'a ≈≈ (Time, 'a)
type Area 'a = Stream (Space 'a)
type Region = Area NodeSnapshot
type Anchor = Signal NodeSnapshot
smap :: ('a -> 'b) -> Signal 'a -> Signal 'b
amap :: ('a -> 'b) -> Area 'a
-> Area 'b
afold :: ('a -> 'b -> 'a) -> 'a -> Area ‘b
-> Signal ('a)
Anchor Free Localization
Anchor Free Localization
Anchor Free Localization
anchorOptimizing ls =
let compare x y =
let loop comps =
case comps of {
[] -> True; -- better break ties somehow
h:t | h x y -> true;
_:t | loop t
}
in loop ls
in anchorWhere (\_ -> True) compare
Anchor Free Localization
between a b = (\ x y ->
abs (dist_from a x
abs (dist_from a y
awayfrom a = (\ x y -> dist_from
awayfrom2 a b = (\ x y ->
abs (dist_from a
abs (dist_from a
n0
n1
n2
n3
n4
n5
=
=
=
=
=
=
anchorOptimizing
anchorOptimizing
anchorOptimizing
anchorOptimizing
anchorOptimizing
anchorOptimizing
- dist_from b x) >
- dist_from b y))
a x > dist_from a y)
x + dist_from b x) >
y + dist_from b y))
[ ]
[awayfrom n0]
[awayfrom n1]
[between n1 n2,
[between n1 n2,
[between n1 n2,
awayfrom2 n1 n2]
awayfrom n3]
between n3 n4]
Example: Contour finding
Example: Threats & Safe path