wifi-densepose/examples/delta-behavior/research/WASM-DELTA-ARCHITECTURE.md

WASM Delta Computation Research Report

Executive Summary

This research analyzes the existing ruvector WASM infrastructure and designs a novel delta computation architecture optimized for vector database incremental updates. The proposed system leverages WASM SIMD128, shared memory protocols, and the WASM component model to achieve sub-100µs delta application latency.

---

1. Current WASM Infrastructure Analysis

1.1 Existing WASM Crates in RuVector

Crate	Purpose	Delta Relevance
ruvector-wasm	Core VectorDB bindings	Memory protocol foundation
ruvector-gnn-wasm	Graph Neural Networks	Node embedding deltas
ruvector-graph-wasm	Graph database	Structure deltas
ruvector-learning-wasm	MicroLoRA training	Weight deltas
ruvector-mincut-wasm	Graph partitioning	Partition deltas
ruvector-attention-wasm	Attention mechanisms	KV cache deltas

1.2 Key Patterns Identified

Memory Layout Protocol (from ruvector-wasm/src/kernel/memory.rs):

• 64KB page-aligned allocations
• 16-byte SIMD alignment
• Region-based memory validation
• Zero-copy tensor descriptors

Batch Operations (from ruvector-mincut/src/optimization/wasm_batch.rs):

• TypedArray bulk transfers
• Operation batching to minimize FFI overhead
• 64-byte AVX-512 alignment for SIMD compatibility

SIMD Distance Operations (from simd_distance.rs):

• WASM SIMD128 intrinsics for parallel min/max
• Batch relaxation for Dijkstra-style updates
• Scalar fallback for non-SIMD environments

---

2. WASM Delta Primitives Design

2.1 WIT Interface Definition

// delta-streaming.wit
package ruvector:delta@0.1.0;

/// Delta operation types for incremental updates
enum delta-operation {
    insert,
    update,
    delete,
    batch-update,
    reindex-layers,
}

/// Delta header for streaming protocol
record delta-header {
    sequence: u64,
    operation: delta-operation,
    vector-id: option<string>,
    timestamp: u64,
    payload-size: u32,
    checksum: u64,
}

/// Delta payload for vector operations
record vector-delta {
    id: string,
    changed-dims: list<u32>,
    new-values: list<f32>,
    metadata-delta: list<tuple<string, string>>,
}

/// HNSW index delta for graph structure changes
record hnsw-delta {
    layer: u8,
    add-edges: list<tuple<u32, u32, f32>>,
    remove-edges: list<tuple<u32, u32>>,
    entry-point-update: option<u32>,
}

/// Delta stream interface for producers
interface delta-capture {
    init-capture: func(db-id: string, config: capture-config) -> result<capture-handle, delta-error>;
    start-capture: func(handle: capture-handle) -> result<_, delta-error>;
    poll-deltas: func(handle: capture-handle, max-batch: u32) -> result<list<delta-header>, delta-error>;
    get-payload: func(handle: capture-handle, sequence: u64) -> result<list<u8>, delta-error>;
    checkpoint: func(handle: capture-handle) -> result<checkpoint-marker, delta-error>;
}

/// Delta stream interface for consumers
interface delta-apply {
    init-apply: func(db-id: string, config: apply-config) -> result<apply-handle, delta-error>;
    apply-delta: func(handle: apply-handle, header: delta-header, payload: list<u8>) -> result<u64, delta-error>;
    apply-batch: func(handle: apply-handle, deltas: list<tuple<delta-header, list<u8>>>) -> result<batch-result, delta-error>;
    current-position: func(handle: apply-handle) -> result<u64, delta-error>;
    seek: func(handle: apply-handle, sequence: u64) -> result<_, delta-error>;
}

2.2 Memory Layout for Delta Structures

Delta Ring Buffer Memory Layout (64KB pages):
+------------------------------------------------------------------+
| Page 0-3: Delta Headers (64KB total)                              |
| +--------------------------------------------------------------+ |
| | Header 0     | Header 1     | Header 2     | ...              | |
| | [64 bytes]   | [64 bytes]   | [64 bytes]   |                  | |
| +--------------------------------------------------------------+ |
|                                                                  |
| Header Structure (64 bytes, cache-line aligned):                 |
| +--------------------------------------------------------------+ |
| | sequence: u64          | 8 bytes                              | |
| | operation: u8          | 1 byte                               | |
| | flags: u8              | 1 byte                               | |
| | reserved: u16          | 2 bytes                              | |
| | vector_id_hash: u32    | 4 bytes                              | |
| | timestamp: u64         | 8 bytes                              | |
| | payload_offset: u32    | 4 bytes                              | |
| | payload_size: u32      | 4 bytes                              | |
| | checksum: u64          | 8 bytes                              | |
| | prev_sequence: u64     | 8 bytes (for linked list)           | |
| | padding: [u8; 16]      | 16 bytes (to 64)                     | |
| +--------------------------------------------------------------+ |
+------------------------------------------------------------------+
| Pages 4-N: Delta Payloads (variable)                             |
| +--------------------------------------------------------------+ |
| | Compressed delta data                                         | |
| | [SIMD-aligned, 16-byte boundary]                              | |
| +--------------------------------------------------------------+ |
+------------------------------------------------------------------+

---

3. Novel WASM Delta Architecture

3.1 Architecture Diagram

+=====================================================================+
|                     DELTA HOST RUNTIME                               |
+=====================================================================+
|                                                                      |
|  +-------------------------+     +-----------------------------+     |
|  |   Change Capture        |     |     Delta Apply Engine      |     |
|  |   (Producer Side)       |     |     (Consumer Side)         |     |
|  +-------------------------+     +-----------------------------+     |
|  | - Vector write hooks    |     | - Sequence validation       |     |
|  | - HNSW mutation capture |     | - Conflict detection        |     |
|  | - Batch accumulation    |     | - Parallel application      |     |
|  | - Compression pipeline  |     | - Index maintenance         |     |
|  +-------------------------+     +-----------------------------+     |
|           |                                    |                     |
|           v                                    v                     |
|  +===========================================================+      |
|  |            SHARED DELTA MEMORY (WebAssembly.Memory)        |      |
|  +===========================================================+      |
|  |  +-------------+  +-------------+  +-------------------+   |      |
|  |  | Capture     |  | Process     |  | Apply             |   |      |
|  |  | WASM Module |  | WASM Module |  | WASM Module       |   |      |
|  |  +-------------+  +-------------+  +-------------------+   |      |
|  |  | - Intercept |  | - Filter    |  | - Decompress      |   |      |
|  |  | - Serialize |  | - Transform |  | - SIMD apply      |   |      |
|  |  | - Compress  |  | - Route     |  | - Index update    |   |      |
|  |  +-------------+  +-------------+  +-------------------+   |      |
|  |       |               |                  |                 |      |
|  |       v               v                  v                 |      |
|  |  +===========================================================+   |
|  |  |                 DELTA RING BUFFER                         |   |
|  |  +===========================================================+   |
|  +===========================================================+      |
|                                                                      |
+=====================================================================+

3.2 Three-Stage Delta Pipeline

/// Stage 1: Capture WASM Module
#[wasm_bindgen]
pub struct DeltaCaptureModule {
    sequence: AtomicU64,
    pending: RingBuffer<DeltaHeader>,
    compressor: LZ4Compressor,
    stats: CaptureStats,
}

impl DeltaCaptureModule {
    /// SIMD-accelerated diff computation
    #[cfg(target_feature = "simd128")]
    fn compute_diff(&self, old: &[f32], new: &[f32]) -> Vec<(u32, f32)> {
        use core::arch::wasm32::*;

        let mut changes = Vec::new();
        let epsilon = f32x4_splat(1e-6);

        for (i, chunk) in old.chunks_exact(4).enumerate() {
            let old_v = v128_load(chunk.as_ptr() as *const v128);
            let new_v = v128_load(new[i*4..].as_ptr() as *const v128);

            let diff = f32x4_sub(new_v, old_v);
            let abs_diff = f32x4_abs(diff);
            let mask = f32x4_gt(abs_diff, epsilon);

            if v128_any_true(mask) {
                for j in 0..4 {
                    let idx = i * 4 + j;
                    if (old[idx] - new[idx]).abs() > 1e-6 {
                        changes.push((idx as u32, new[idx]));
                    }
                }
            }
        }
        changes
    }
}

/// Stage 3: Apply WASM Module
impl DeltaApplyModule {
    /// Apply single delta with SIMD acceleration
    #[cfg(target_feature = "simd128")]
    pub fn apply_vector_delta_simd(
        &mut self,
        vector_ptr: *mut f32,
        dim_indices: &[u32],
        new_values: &[f32],
    ) -> Result<u64, DeltaError> {
        use core::arch::wasm32::*;

        let start = std::time::Instant::now();

        // Process 4 updates at a time using SIMD
        let chunks = dim_indices.len() / 4;

        for i in 0..chunks {
            let idx_base = i * 4;
            let val_v = v128_load(new_values[idx_base..].as_ptr() as *const v128);

            for j in 0..4 {
                let idx = dim_indices[idx_base + j] as usize;
                unsafe { *vector_ptr.add(idx) = new_values[idx_base + j]; }
            }
        }

        // Handle remainder
        for i in (chunks * 4)..dim_indices.len() {
            let idx = dim_indices[i] as usize;
            unsafe { *vector_ptr.add(idx) = new_values[i]; }
        }

        Ok(start.elapsed().as_micros() as u64)
    }
}

---

4. Performance Benchmarks Targets

4.1 Delta Operation Latency Targets

Operation	Target Latency	Notes
Single vector insert	<50µs	Zero-copy path
Single vector update (dense)	<30µs	Full vector replacement
Single vector update (sparse)	<10µs	<10% dimensions changed
Vector delete	<20µs	Mark deleted + async cleanup
HNSW edge add (single)	<15µs	Per layer
HNSW edge remove (single)	<10µs	Per layer
Batch insert (100 vectors)	<2ms	Amortized 20µs/vector
Batch update (100 vectors)	<1ms	Amortized 10µs/vector

4.2 Throughput Targets

Metric	Target	Configuration
Delta capture rate	50K deltas/sec	Single producer
Delta apply rate	100K deltas/sec	4 parallel workers
Delta compression ratio	4:1	Typical vector updates
Ring buffer throughput	200MB/sec	Shared memory path

---

5. Lock-Free Ring Buffer

/// Lock-free SPSC ring buffer for delta streaming
#[repr(C, align(64))]
pub struct DeltaRingBuffer {
    capacity: u32,
    mask: u32,
    read_pos: AtomicU64,  // Cache-line padded
    _pad1: [u8; 56],
    write_pos: AtomicU64, // Cache-line padded
    _pad2: [u8; 56],
    headers: *mut DeltaHeader,
    payloads: *mut u8,
}

impl DeltaRingBuffer {
    #[inline]
    pub fn try_reserve(&self, payload_size: u32) -> Option<ReservedSlot> {
        let write = self.write_pos.load(Ordering::Relaxed);
        let read = self.read_pos.load(Ordering::Acquire);

        if write.wrapping_sub(read) >= self.capacity as u64 {
            return None;
        }

        match self.write_pos.compare_exchange_weak(
            write, write + 1, Ordering::AcqRel, Ordering::Relaxed,
        ) {
            Ok(_) => Some(ReservedSlot { sequence: write, /* ... */ }),
            Err(_) => None,
        }
    }
}

---

6. Performance Projections

Scenario	Current (no delta)	With Delta System	Improvement
Single vector update	~500µs	<30µs	16x
Batch 100 vectors	~50ms	<2ms	25x
HNSW reindex	~10ms	<1ms (incremental)	10x
Memory overhead	0	+1MB per database	Acceptable

---

7. Recommended Implementation Order

1. Phase 1: Implement DeltaRingBuffer and basic capture in ruvector-wasm
2. Phase 2: Add SIMD-accelerated apply module with sparse update path
3. Phase 3: Integrate with ruvector-graph-wasm for structure deltas
4. Phase 4: Add WIT interfaces for component model support
5. Phase 5: Implement parallel application with shared memory workers

---

8. Integration with Δ-Behavior

The WASM delta system directly supports Δ-behavior enforcement:

Δ-Behavior Property	WASM Implementation
Local Change	Sparse updates, bounded payload sizes
Global Preservation	Coherence check in apply stage
Violation Resistance	Ring buffer backpressure, validation
Closure Preference	Delta compaction toward stable states

The three-stage pipeline naturally implements the three enforcement layers:

• Capture → Energy cost (compression overhead)
• Process → Scheduling (filtering, routing)
• Apply → Memory gate (validation, commit)