Channel Demo¶

The Channel demo demonstrates how three gradient computations compose to form a logical corridor between a source region and a destination region.

What It Shows¶

Composition of multiple building blocks
Logical path formation between two regions
The channel composite pattern

Building Blocks Used¶

Block	Role
G (gradient from source)	Distance field from source region
G (gradient from destination)	Distance field from destination region
G (combined)	Shortest source-to-destination path length

How It Works¶

The channel is defined as the set of devices that lie "close enough" to the shortest path between source and destination:

def channel_program(ctx):
    is_src = ctx.sense("is_source")
    is_dst = ctx.sense("is_destination")
    return channel(ctx, is_src, is_dst, width=0.5)

The algorithm:

Compute d_s = gradient from source
Compute d_d = gradient from destination
Compute d_sd = the shortest distance between source and destination (broadcast from source along d_s)
A device is on the channel if: \(d_s + d_d \leq d_{sd} + w\)

where \(w\) is the width tolerance.

\[ \text{channel}(\delta) = \bigl(G_{\text{src}}(\delta) + G_{\text{dst}}(\delta)\bigr) \leq \bigl(d_{\text{src} \to \text{dst}} + w\bigr) \]

Network Configuration¶

Parameter	Default	Effect
Topology	Grid	8×8 regular grid
Source	Device 0	Top-left corner
Destination	Device 63	Bottom-right corner
Width	0.5	Corridor tolerance
Comm Range	1.5	Neighbour connectivity

Interpretation¶

Highlighted devices (bright) — on the channel
Dark devices — outside the channel

The channel forms a band of devices connecting the source to the destination. The width parameter controls how wide this band is: a width of 0 gives the exact shortest path, while larger values include more devices.

Composition in Action¶

This demo is a clear example of functional composition in aggregate computing. The channel pattern is built entirely from gradient calls — no new low-level primitives are needed. This compositionality is a key design principle of the building-block approach.

Try It¶

Select Channel from the demo dropdown in the simulator, or try it on the live deployment.