sim14 — Heterogeneous Agents

Open the interactive visualization — renders the grid heatmap (play/pause, step slider) and all metric charts from results.json.

One-line: Agents carry a structure ID; deposits are tagged with the depositor's ID; co-presence checks for material from TWO DISTINCT IDs — so a 1-seed control is structurally zero, regardless of agent wander.

The question

sim13 showed that agent wander (not the torus leak) causes false boundaries: agents on a torus deposit material in both halves, creating real co-presence from a single structure. Every spatial filter — diffusion (sim12), direct-material max filter (sim13) — picks up wander material because it detects WHERE material is, not WHOSE it is.

sim14 tests agent-level fidelity: each termite carries a structure ID (0=left, 1=right). Deposits go into material_by_id[agent.id]. Co-presence = min(dilate(material_by_id[0]), dilate(material_by_id[1])). For a single seed, all agents have id=0, so material_by_id[1] is zero everywhere → co-presence = 0 → B = 0. This is a structural guarantee — no spatial filter can achieve it.

Design

• HeteroTermites: first n//2 agents get id=0 (left), rest get id=1 (right). For 1-seed control, all get id=0.
• Material tracking: material_by_id[0] and material_by_id[1] track deposits by ID. Total field.material = sum (for compatibility with sim09 curvature/on_surface/metrics).
• Deposits: material_by_id[agent.id] += pellet AND field.material += pellet.
• Excavation: proportional removal from both ID arrays.
• Co-presence: min(dilate_no_x_wrap(material_by_id[0]), dilate_no_x_wrap(material_by_id[1])) — sim13's max filter, but on ID-separated arrays.
• Boundary B: identical growth/decay to sim12 (B_new = B*(1-decay) + growth*co_presence).
• Suppression: identical to sim12 (p_dep *= (1 - g*B_norm/(1+B_norm))).

Results

8-Condition experiment (seed 42, g=0.9)

4-Seed robustness sweep

Key findings

1. The 1-seed control is 0/4 on ALL metrics. l2_crossed=0/4, coexist=0/4, stable=0/4, B_max=0.0 across all seeds. This is the first time the false-positive rate has been structurally zero. No spatial filter achieves this — sim12's shadow has 4/4 l2_false positives, sim13's direct-material has 4/4 l2 and 1/4 coexist.

2. Clean composition: 2/4 — matching shadow and passive. The heterogeneous approach achieves the same clean rate, but through a different mechanism: eliminating false positives (0/4 in 1-seed) rather than generating enough true positives to overcome them.

3. H7 crossing suppressed: 0/4. The ID-based boundary is too strong — it suppresses growth below the H7 crossing threshold (cells: 167 vs 3714 for shadow). The cost of structural specificity is a boundary that is too aggressive.

4. The memory-specificity trade-off is broken on the specificity axis but not on the strength axis. Agent IDs eliminate false positives (specificity), but the boundary's strength (memory) needs tuning — the same trade-off in a new form.

Selftest

All 7 parts pass: ID co-presence high for 2 seeds (1.83), EXACTLY zero for 1 seed (max=0.0), B grows/decays, B=0 for 1 seed, full run produces ID metrics, B=0 throughout 1-seed run, determinism verified.

Comparison to previous simulations

sim14 is the first approach where the 1-seed control fires 0/4 on l2_crossed. The structural guarantee (id1 material = 0 for a single seed) is absolute — it cannot be broken by agent wander, torus topology, or boundary radius.

Limitations

• H7 crossing suppressed (0/4). The boundary is too strong at g=0.9. A lower inh_gain might allow both crossing and composition — but that is a parameter-tuning question, not a mechanism question.
• 2/4 coexist, not higher. The same rate as passive and shadow. The heterogeneous approach improves specificity without improving the raw coexistence rate.
• Agents still wander freely. The IDs tag deposits, not movement. Agents from the left can still wander to the right and deposit there — their deposits carry id=0, which doesn't create false co-presence, but it does mean the boundary's spatial location is still determined by where agents deposit, which is influenced by wander.

Files

• sim14.py — the simulation (imports sim13/sim12/sim11/sim10/sim09)
• results.json — 8-condition experiment
• output/robustness_sweep.json — 4-seed robustness sweep
• visualize.html — interactive visualization

Run

python3 sim14.py selftest     # 7-part selftest
python3 sim14.py run         # 8-condition experiment
python3 sim14.py robustness  # 4-seed robustness sweep

Density Scaling (Session 41)

Queued-topic #119: does scaling n_termites with grid area rescue the 160×160 grid's degradation?

H7 fully rescued by density (4/4 at all jitter). Composition partially rescued (4/4 at jit=0, 3/4 stable at jit=10, 2/4 at jit=20). 1-seed structural guarantee leaks at 160×600 (absolute-size effect — bigger structure overwhelms midline). See density_sweep.py.

N550 Plateau (Session 66)

Queued-topic #157/#161: does g* ever hit zero at n=550–600 (~31% grid fill)?

g does NOT hit zero.* The 1/√n scaling holds at ~31% fill. H7=4/4 at all combos. n=550 g=0.01 achieves 4/4 full (cf=0.712). The LSW "droplet dissolves" prediction is not realized — ~31% fill is far below the 2D percolation threshold (~59%). The 43rd mechanism: the 1/√n scaling is conservative (actual optimal > predicted). The 30th mechanism (stability-density trade-off) continues at n=600. See n550_plateau_sweep.py.

No-inhibition control: n=550 g=0 → 3/4 coexist, 1/4 stable, cells=15691 (61% fill). n=600 g=0 → 0/4 coexist, cells=17020 (66% fill). The boundary remains necessary at every density.

N700 Plateau (Session 67)

Queued-topic #157 (continuation): does g* hit zero at n=700–800 (~33–35% grid fill)? The 1/√n formula predicts NEGATIVE g* at n=700–800 — the 43rd mechanism says actual > predicted.

g does NOT hit zero.* The 43rd mechanism (conservative scaling) confirmed: the 1/√n formula predicts NEGATIVE g* but actual g* is positive. H7=4/4 at all 8 combos. n=800 g=0.003 achieves 3/4 full (cf=0.575). The 30th mechanism (stability-density trade-off) worsens at n=800 g=0.01 (coexist 1/4, 3/4 fragmented). The 1-seed structural guarantee degrades: 1/4 at n=700, 3/4 at n=800. See n700_plateau_sweep.py.

No-inhibition control: n=700 g=0 → 0/4 coexist, cells=18954 (74% fill). n=800 g=0 → 2/4 coexist (measurement artifact at 82% fill), cells=20960. The boundary remains necessary at every density tested.

N900 Plateau (Session 68)

Queued-topic #157 (continuation): does g* hit zero at n=900–1000 (~36% grid fill)? The 1/√n formula predicts deeply NEGATIVE g* (g*≈-0.44 to -0.47) — the 43rd mechanism says actual > predicted.

g does NOT hit zero.* The 43rd mechanism (conservative scaling) confirmed at a third density range: the 1/√n formula predicts deeply NEGATIVE g* but actual g* is positive. H7=4/4 at all 8 combos. n=900 g=0.01 achieves 2/4 full (cf=0.525). The 30th mechanism (stability-density trade-off) persists: stable 0–2/4. The 1-seed structural guarantee is stochastic, not monotonic: 1/4 at n=900, 4/4 at n=1000 — the 12th member does not degrade monotonically. See n900_plateau_sweep.py.

No-inhibition control: n=900 g=0 → 0/4 coexist, cells=22240 (87% fill). n=1000 g=0 → 0/4 coexist (1/4 l2_crossed artifact at 92% fill), cells=23519. The boundary remains necessary — it prevents percolation.