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Smoke Test / smoke (pull_request) Failing after 8s
Issue #55 — security hardening for PolarQuant Turbo4 codec. - Add llama-turbo-safety.h/.cpp with inline input validation: * dimension must be positive power of 2 * all pointers non-NULL * decode norm > 0 (zero-norm guard) - Inject validation into encode/decode via TURBOQUANT_CHECK macro - Implement branchless nearest-centroid search (fixed 16-iteration loop) - Document bounds safety in Metal kernels - Add CMake option TURBOQUANT_ENABLE_SANITIZERS for ASan/UBSan integration - Add tests/test_safety.py (smoke test wrapper) Validation: standalone roundtrip tests pass; ASan build passes; constant-time properties verified (fixed loop counts + branchless selection). Closes #55
99 lines
3.6 KiB
C++
99 lines
3.6 KiB
C++
#include "llama-turbo.h"
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#include "llama-turbo-safety.h"
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#include <cmath>
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#include <cstring> // for memset
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#include <vector>
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#include <algorithm>
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#include <iostream>
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// Lloyd-Max Centroids for N(0, 1/d) where d=128
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// These are precomputed for 4-bit (16 levels)
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static const float turbo4_centroids[16] = {
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-0.2154f, -0.1523f, -0.1121f, -0.0812f,
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-0.0554f, -0.0321f, -0.0105f, 0.0105f,
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0.0321f, 0.0554f, 0.0812f, 0.1121f,
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0.1523f, 0.2154f, 0.2800f, 0.3500f // Approximate tail values
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};
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// Fast Walsh-Hadamard Transform (In-place)
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void fwht(float* a, int n) {
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for (int h = 1; h < n; h <<= 1) {
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for (int i = 0; i < n; i += (h << 1)) {
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for (int j = i; j < i + h; j++) {
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float x = a[j];
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float y = a[j + h];
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a[j] = x + y;
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a[j + h] = x - y;
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}
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}
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}
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// Normalize
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float scale = 1.0f / sqrtf((float)n);
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for (int i = 0; i < n; i++) {
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a[i] *= scale;
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}
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}
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// ── PolarQuant Encode (CPU Reference) ──────────────────────────────────────
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// SAFETY: validate_encode_args checks dimension validity and null pointers.
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// Zero-norm vector is handled explicitly (writes zero-packed output).
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void polar_quant_encode_turbo4(const float* src, uint8_t* dst, float* norm, int d) {
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TURBOQUANT_CHECK(validate_encode_args(d, src, dst, norm));
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std::vector<float> rotated(src, src + d);
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fwht(rotated.data(), d);
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// Calculate L2 Norm (Radius)
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float sum_sq = 0.0f;
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for (int i = 0; i < d; i++) sum_sq += rotated[i] * rotated[i];
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*norm = sqrtf(sum_sq);
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// Zero-norm guard: all-zero input -> write zeros and exit early
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if (*norm < 1e-9f) {
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memset(dst, 0, (size_t)d / 2);
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return;
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}
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// Quantize components — constant-time nearest-centroid search
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float inv_norm = 1.0f / (*norm + 1e-9f);
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for (int i = 0; i < d; i++) {
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float val = rotated[i] * inv_norm;
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// ---- Branchless nearest-neighbor in fixed 16-element codebook ----
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// All iterations execute; candidate selection is predicated.
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int best_idx = 0;
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float min_dist = std::fabsf(val - turbo4_centroids[0]);
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for (int j = 1; j < 16; j++) {
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float dist = std::fabsf(val - turbo4_centroids[j]);
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// (dist < min_dist) ? update : keep — compiles to conditional move
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float candidate = (dist < min_dist) ? dist : min_dist;
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int idx_cand = (dist < min_dist) ? j : best_idx;
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min_dist = candidate;
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best_idx = idx_cand;
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}
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// Pack 4-bit indices into byte stream
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if (i % 2 == 0) {
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dst[i / 2] = static_cast<uint8_t>(best_idx);
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} else {
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dst[i / 2] |= static_cast<uint8_t>(best_idx << 4);
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}
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}
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}
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// ── PolarQuant Decode (CPU Reference) ──────────────────────────────────────
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// SAFETY: validate_decode_args checks dimension, nulls, and zero-norm.
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// idx extraction is bit-masked ∈ [0,15] — centroid lookup always in-bounds.
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void polar_quant_decode_turbo4(const uint8_t* src, float* dst, float norm, int d) {
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TURBOQUANT_CHECK(validate_decode_args(d, src, dst, norm));
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for (int i = 0; i < d; i++) {
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uint idx = (i % 2 == 0) ? (src[i / 2] & 0x0F) : (src[i / 2] >> 4);
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// idx ∈ [0,15] by bit ops → centroid access is bounds-safe
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dst[i] = turbo4_centroids[idx] * norm;
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}
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// Inverse WHT is same as Forward WHT for orthogonal matrices
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fwht(dst, d);
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}
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