Scaling Strategies

This document describes how to scale the Screeps AI from a single room to multiple rooms while maintaining efficiency and staying within CPU limits.

Overview

Scaling in Screeps involves managing increasing numbers of creeps, rooms, and structures while staying within the CPU limit. This requires careful planning and incremental expansion.

Room Control Level (RCL) Progression

RCL 1: Foundation

Characteristics:

1 spawn available
1-2 sources accessible
300 energy capacity (spawn only)
No extensions

Optimal Composition:

2 Harvesters (minimum viable economy)
1 Upgrader (controller maintenance)
Total: 3 creeps

CPU Budget: ~2-3 CPU/tick

Memory management: ~0.1 CPU
Spawn logic: ~0.1 CPU
3 creeps × 0.5 CPU: ~1.5 CPU
Kernel overhead: ~0.5 CPU

Energy Flow:

Income: ~10 energy/tick (2 harvesters, 1 source)
Spawn cost: ~1.4 energy/tick average
Upgrade rate: ~0.8 energy/tick
Surplus: ~7.8 energy/tick (enables upgrades)

Bottleneck: Energy storage (300 capacity limits growth)

RCL 2: Expansion

Unlocks:

5 extensions (50 energy each) = +250 energy capacity
Ramparts and walls
Total capacity: 550 energy

Optimal Composition:

3-4 Harvesters (2 per source ideal)
1-2 Upgraders (consume surplus energy)
0-1 Builder (bootstrap road/ramp construction as extensions unlock)
Total: 4-6 creeps

CPU Budget: ~3-5 CPU/tick

Energy Flow:

Income: ~15-20 energy/tick (3-4 harvesters, 2 sources)
Spawn cost: ~2 energy/tick average (more frequent spawning)
Upgrade rate: ~1-2 energy/tick (1-2 upgraders)
Surplus: ~12-17 energy/tick

Scaling Decision:

Add 3rd harvester when spawn queue >3
Add 2nd upgrader when spawns at capacity >20% of time

Bottleneck: Spawn availability (single spawn limits throughput)

RCL 3: Infrastructure

Unlocks:

10 extensions (50 energy each) = +500 energy capacity
Towers
Total capacity: 800 energy

Optimal Composition:

4-5 Harvesters
2-3 Upgraders
1 Builder (continuous road/extension maintenance)
0-1 Remote Miner (pilot route to nearby source if safe)
Total: 6-9 creeps

CPU Budget: ~5-8 CPU/tick

Energy Flow:

Income: ~20-25 energy/tick
Spawn cost: ~2.5 energy/tick
Upgrade rate: ~2-3 energy/tick
Tower defense: ~0-5 energy/tick (sporadic)
Surplus: ~10-15 energy/tick

Scaling Decision:

Add 5th harvester if sources underutilized
Add 3rd upgrader if consistent energy surplus
CPU becomes a consideration (monitor bucket)

Bottleneck: CPU efficiency and spawn throughput

RCL 4+: Optimization

Unlocks (RCL 4):

20 extensions (50 energy each) = +1000 energy capacity
Storage structure (unlimited capacity)
Total capacity: 1300 energy

Focus: Optimize for efficiency before expanding further

Optimal Composition:

2 Harvesters per source (4-6 total)
3-5 Upgraders
1-2 Builders (for infrastructure and repairs)
1-2 Remote Miners (sustain remote sources feeding storage)
Total: 8-13 creeps

CPU Budget: ~8-15 CPU/tick

Optimization Goals:

Reduce per-creep CPU cost
Implement better pathfinding
Add energy storage management
Prepare for multi-room expansion

Multi-Room Expansion Strategy

When to Expand

Prerequisites:

Current room at RCL 4+
Stable economy (10+ energy/tick surplus)
CPU bucket >5000 (safety margin)
Storage structure active
Remote miner routes established with safe travel corridors

Expansion Checklist:

Claim new room with controller
Build first spawn in new room
Establish energy supply chain
Monitor CPU usage increase

Room Claim Process

Step 1: Scout and Claim

Create claimer creep (1 CLAIM, 1 MOVE)
Move to target room
Use claimController() action
Cost: ~650 energy + 1 CPU/tick during travel

Step 2: Remote Harvesting

Assign dedicated remote miner creeps to target sources
Provide hauler or builder support once containers are placed
Establish energy pipeline
Build first spawn foundation
Cost: ~5000 energy for spawn, ~2-3 CPU/tick

Step 3: Bootstrap New Room

Wait for spawn construction (15000 ticks = ~100 real-time hours)
Spawn first creeps in new room
Gradually reduce remote harvesting
Cost: Temporary energy drain, +2-3 CPU/tick

Multi-Room CPU Budget

CPU Distribution:

Main Room (RCL 6):     ~15 CPU/tick
Secondary Room (RCL 2): ~3 CPU/tick
Kernel + Memory:        ~1 CPU/tick
─────────────────────────────────
Total:                 ~19 CPU/tick

CPU Limit Considerations:

Subscription: 30 CPU/tick
Free tier: 10 CPU/tick (insufficient for 2+ rooms)
Recommendation: Subscribe before claiming 2nd room

Creep Body Scaling

Early Game Bodies (RCL 1-2)

Harvester: [WORK, CARRY, MOVE]

Cost: 50 energy
Harvest rate: 2/tick
Capacity: 50 energy
Speed: 1 tile/tick

Upgrader: [WORK, CARRY, MOVE]

Cost: 50 energy
Upgrade rate: 1 point/energy
Capacity: 50 energy
Speed: 1 tile/tick

Mid Game Bodies (RCL 3-4)

Harvester: [WORK, WORK, CARRY, MOVE, MOVE]

Cost: 300 energy
Harvest rate: 4/tick (2× faster)
Capacity: 50 energy (same)
Speed: 1 tile/tick (balanced)

Upgrader: [WORK, WORK, CARRY, CARRY, MOVE, MOVE]

Cost: 350 energy
Upgrade rate: 2 points/energy (2× faster)
Capacity: 100 energy (2× larger)
Speed: 1 tile/tick (balanced)

Late Game Bodies (RCL 5+)

Harvester: [WORK, WORK, WORK, CARRY, CARRY, MOVE, MOVE, MOVE]

Cost: 550 energy
Harvest rate: 6/tick (3× faster)
Capacity: 100 energy
Speed: 1 tile/tick
Efficiency: Fewer creeps needed (reduces CPU)

Upgrader: [WORK, WORK, WORK, WORK, CARRY, CARRY, CARRY, CARRY, MOVE, MOVE, MOVE, MOVE]

Cost: 800 energy
Upgrade rate: 4 points/energy (4× faster)
Capacity: 200 energy (4× larger)
Speed: 1 tile/tick
Efficiency: Significantly reduces upgrader count

Scaling Decision Matrix

Add Harvester When:

Symptom	Metric	Action
Spawns empty	`spawn.store.energy < 50` >50% ticks	+1 Harvester
Sources underutilized	<2 creeps per source	+1 Harvester per source
Spawn queue depth	>5 pending creeps	+1 Harvester
Controller downgrade	<5000 ticks to downgrade	+1 Harvester

Add Upgrader When:

Symptom	Metric	Action
Spawns at capacity	`spawn.store.energy === 300` >20% ticks	+1 Upgrader
Energy surplus	Consistent 10+ energy/tick surplus	+1 Upgrader
Slow RCL progress	<500 control points/1000 ticks	+1 Upgrader
CPU available	Bucket >8000, current usage <80% limit	+1 Upgrader

Reduce Creeps When:

Symptom	Metric	Action
CPU bucket draining	Bucket <2000 and decreasing	Reduce upgraders first
Excessive idle time	Creeps idle >20% of ticks	Reduce role count
Over-harvesting	Energy waste visible	Reduce harvester count

CPU Optimization Strategies

Pathfinding Optimization

Current Implementation: reusePath: 5

Recalculates path every 5 ticks
Cost: ~0.5 CPU per recalculation
Optimization: Increase to reusePath: 10 for stable rooms
Savings: ~50% pathfinding CPU

Memory Access Optimization

Current Implementation: Direct Memory access each tick

Cost: ~0.1 CPU per creep per tick
Optimization: Cache frequently accessed memory in local variables
Savings: ~20-30% memory access CPU

Role-Specific Optimization

Harvester Optimization:

Assign to specific sources (prevents competition)
Use container mining (reduces movement)
Potential savings: 15-25% harvester CPU

Upgrader Optimization:

Position statically near controller
Use link for energy delivery (late game)
Potential savings: 30-40% upgrader CPU

Scaling Benchmarks

Single Room Performance

RCL	Creeps	CPU/tick	Energy/tick	Upgrade Rate	Bucket Trend
1	3	2-3	10	0.8	Stable
2	5	3-5	18	1.5	Increasing
3	8	5-8	23	2.5	Stable
4	10	8-12	28	3.5	Stable
5	12	10-15	35	5.0	Stable
6	14	12-18	40	7.0	Decreasing*

*At RCL 6, CPU optimization becomes critical for free tier users.

Multi-Room Performance

Total Rooms	Total Creeps	CPU/tick	Subscription	Viable?
1	8-12	8-15	No	✓ Yes
2	18-24	18-25	Required	✓ Yes
3	30-38	28-38	Required	✓ Yes
4+	40+	38+	Required	Careful

Note: CPU limit with subscription is typically 30 CPU/tick for most players.

Scaling Failure Modes

CPU Bucket Depletion

Symptoms:

Bucket drops below 500
Warning: “CPU bucket is depleted”
Game execution may be throttled

Recovery:

Reduce upgrader count immediately
Increase path reuse duration
Monitor bucket recovery
Identify CPU-intensive operations

Spawn Starvation

Symptoms:

Spawns empty most ticks
Creep population declining
Controller downgrade timer low

Recovery:

Add emergency harvester (highest priority)
Disable upgraders temporarily
Focus all energy on spawning harvesters
Resume normal operations once stable

Controller Downgrade

Symptoms:

controller.ticksToDowngrade < 5000
Warning: “Controller will downgrade soon”
RCL progress negative

Recovery:

Add upgraders immediately
Ensure harvesters deliver to upgraders
Sacrifice other operations for upgrades
Monitor downgrade timer until >10000

Creep Roles - Role definitions and body configurations
Task Prioritization - Task efficiency and optimization
Performance Monitoring - CPU tracking and alerting
Memory Management - Memory optimization for scaling

Scaling Strategies

Overview

Room Control Level (RCL) Progression

RCL 1: Foundation

RCL 2: Expansion

RCL 3: Infrastructure

RCL 4+: Optimization

Multi-Room Expansion Strategy

When to Expand

Room Claim Process

Multi-Room CPU Budget

Creep Body Scaling

Early Game Bodies (RCL 1-2)

Mid Game Bodies (RCL 3-4)

Late Game Bodies (RCL 5+)

Scaling Decision Matrix

Add Harvester When:

Add Upgrader When:

Reduce Creeps When:

CPU Optimization Strategies

Pathfinding Optimization

Memory Access Optimization

Role-Specific Optimization

Scaling Benchmarks

Single Room Performance

Multi-Room Performance

Scaling Failure Modes

CPU Bucket Depletion

Spawn Starvation

Controller Downgrade

Related Documentation