memlnaut-nisps/nisps/ml/storage.hpp
monkey-w1n5t0n dbe0f5d8ba fix(ml): one named example capacity; train() and trainAsync() no longer diverge
Phase 2, S35. Two real defects from one root cause, both confirmed by trace
rather than taken from the audit:

1. Divergence. WasmIML built its TS Dataset mirror with a cap of 100 while
   every addExample() ALSO pushed into the C++ FIFO ring, capped at 128. Since
   train() reads the C++ ring and trainAsync() reads the TS mirror, past 100
   examples the two trained on different datasets — silently.
2. Latent OOB read. nisps_ml_train sizes its sample-weight span by the C++
   side's example_count() (up to 128), but wasm-iml.ts allocates that heap
   buffer from the TS dataset's size (<=100). Once the ring exceeds the mirror,
   the span reads past the end of the caller's allocation.

Fix: name the capacity ONCE as nisps::ml::kDefaultMaxExamples = 128, used by
FixedStorage's default template arg, DynamicStorage's default ctor arg, and the
MLP<> alias (which is the only real FixedStorage instantiation path and carried
its own independent 128 literal — the last copy of this dual truth). Expose it
through nisps_ml_describe and have the TS side read it instead of hardcoding.
Dataset's constructor default is removed entirely: a default was what invited
this bug class, and the sole call site now always supplies the describe() value.

ABI NOTE: this extends nisps_ml_describe from a 6-int to a 7-int descriptor.
nisps_ml_describe always writes 7 ints regardless of the caller's buffer, so
every call site had to grow in the same change or it would overflow the WASM
heap by 4 bytes per call. All five sites updated: three in wasm-iml.ts (init
defaults, init per-instance, reshape re-describe — the finding said there were
two), one in wasm-worker.ts, one in tests/cpp/parity_wasm.mjs. The parity
harness's expected-dims check now also pins the new max_examples slot.

Regression test: tests/cpp/test_mlp_storage_defaults.cpp — pins the two storage
policies to one constant, and drives MLPCore<DynamicStorage> exactly as
bindings.cpp does past the old TS cap, asserting it saturates at 128 and not at
100. Fail-before/pass-after confirmed by temporarily setting the constant to
100: 2 failures, named. Reverted: green.

Audit correction: the cited dataset.ts:81 is the FIFO eviction check; the
hardcoded default was at dataset.ts:45.

Gates: run-all-tests.sh ALL GREEN, parity PASS.
2026-07-21 13:22:38 +02:00

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C++

// nisps/ml/storage.hpp — storage policies for the MLP core (fixed flavour).
//
// The MLP algorithms (nisps/ml/mlp.hpp `MLPCore<Storage>`) are written ONCE
// against a storage concept; the storage supplies every dimension and every
// buffer. Two models exist:
//
// * `FixedStorage<NIn, NH1, NH2, NH3, NOut, NMaxExamples, NMaxIterTrain>`
// (this file) — all buffers are template-sized `std::array`, zero heap.
// This is the firmware model; the classic
// `MLP<...>` template is an alias over it and its compile-time constants
// (`kInput`, `kHidden1..3`, `kOutput`, `weight_count()`) are preserved.
//
// * `DynamicStorage` (nisps/ml/dynamic_storage.hpp) — dimensions chosen at
// construction, one arena allocation, no allocation after construction.
// Compile-time EXCLUDED from embedded builds (see NISPS_TARGET_EMBEDDED
// in nisps/core/perf.hpp).
//
// STORAGE SURFACE (both models; L is the layer index 0..3)
// dims: n_in(), n_out(), fan_in_l<L>(), fan_out_l<L>(),
// max_examples(), max_iter_train(), weight_count()
// layers: weights_l<L>(), biases_l<L>(), pre_act_l<L>(), act_l<L>(),
// grad_w_l<L>(), grad_b_l<L>(), delta_l<L>() [backprop scratch,
// sized fan_in(L)], eval_act_l<L>() [const-eval scratch,
// sized fan_out(L), mutable]
// global: input_buf(), output_buf(), ds_features(), ds_labels(),
// flat_buf(), loss_hist_buf(), copy_weights_to(dst)
//
// For `FixedStorage` every dim accessor is constexpr-foldable, so the
// algorithms compile to the same fully-unrolled/constant-bound code the old
// hand-fixed MLP produced (verified against the RP2350 `.text` budget —
// chokepoint B of docs/specs/plans/one-core-engine-refactor.md).
//
// Bit-parity contract: for identical shapes and seeds, MLPCore over
// FixedStorage and DynamicStorage must produce bit-identical results — the
// algorithm code is shared and the buffers are just memory. A ctest enforces
// this (tests/cpp/test_mlp_storage_parity.cpp).
#pragma once
#include <array>
#include <cstddef>
#include <span>
#include "../core/perf.hpp"
namespace nisps::ml {
inline constexpr std::size_t kMlpNumLayers = 4u;
// Default example-store capacity, named ONCE and shared by FixedStorage's
// compile-time default (below) and DynamicStorage's runtime-default
// constructor argument (nisps/ml/dynamic_storage.hpp). `nisps_ml_describe`
// (nisps/wasm/bindings.cpp) reports the live instance's max_examples() so
// the Manifold TS side (manifold/src/engine/wasm-iml.ts) can size its JS
// Dataset mirror to match instead of hardcoding a second, divergent number
// (see docs/specs/recon/simplification-audit-2026-07.md S35).
inline constexpr std::size_t kDefaultMaxExamples = 128u;
template <std::size_t NIn,
std::size_t NHidden1,
std::size_t NHidden2,
std::size_t NHidden3,
std::size_t NOut,
std::size_t NMaxExamples = kDefaultMaxExamples,
std::size_t NMaxIterTrain = 4096u>
class FixedStorage {
public:
static constexpr std::size_t kInput = NIn;
static constexpr std::size_t kHidden1 = NHidden1;
static constexpr std::size_t kHidden2 = NHidden2;
static constexpr std::size_t kHidden3 = NHidden3;
static constexpr std::size_t kOutput = NOut;
static constexpr std::size_t kMaxExamples = NMaxExamples;
static constexpr std::size_t kMaxIterTrain = NMaxIterTrain;
static constexpr std::size_t kNumLayers = kMlpNumLayers;
static constexpr std::size_t weight_count() noexcept {
return NIn * NHidden1 + NHidden1 * NHidden2 + NHidden2 * NHidden3 + NHidden3 * NOut
+ NHidden1 + NHidden2 + NHidden3 + NOut;
}
// ---- dims -----------------------------------------------------------
static constexpr std::size_t n_in() noexcept { return NIn; }
static constexpr std::size_t n_out() noexcept { return NOut; }
static constexpr std::size_t max_examples() noexcept { return NMaxExamples; }
static constexpr std::size_t max_iter_train() noexcept { return NMaxIterTrain; }
template <std::size_t L>
static constexpr std::size_t fan_in_l() noexcept {
static_assert(L < kNumLayers);
if constexpr (L == 0u) return NIn;
else if constexpr (L == 1u) return NHidden1;
else if constexpr (L == 2u) return NHidden2;
else return NHidden3;
}
template <std::size_t L>
static constexpr std::size_t fan_out_l() noexcept {
static_assert(L < kNumLayers);
if constexpr (L == 0u) return NHidden1;
else if constexpr (L == 1u) return NHidden2;
else if constexpr (L == 2u) return NHidden3;
else return NOut;
}
// ---- per-layer buffers ------------------------------------------------
template <std::size_t L> NISPS_FORCE_INLINE std::span<float> weights_l() noexcept {
if constexpr (L == 0u) return w0_; else if constexpr (L == 1u) return w1_;
else if constexpr (L == 2u) return w2_; else return w3_;
}
template <std::size_t L> NISPS_FORCE_INLINE std::span<const float> weights_l() const noexcept {
if constexpr (L == 0u) return w0_; else if constexpr (L == 1u) return w1_;
else if constexpr (L == 2u) return w2_; else return w3_;
}
template <std::size_t L> NISPS_FORCE_INLINE std::span<float> biases_l() noexcept {
if constexpr (L == 0u) return b0_; else if constexpr (L == 1u) return b1_;
else if constexpr (L == 2u) return b2_; else return b3_;
}
template <std::size_t L> NISPS_FORCE_INLINE std::span<const float> biases_l() const noexcept {
if constexpr (L == 0u) return b0_; else if constexpr (L == 1u) return b1_;
else if constexpr (L == 2u) return b2_; else return b3_;
}
template <std::size_t L> NISPS_FORCE_INLINE std::span<float> pre_act_l() noexcept {
if constexpr (L == 0u) return pa0_; else if constexpr (L == 1u) return pa1_;
else if constexpr (L == 2u) return pa2_; else return pa3_;
}
template <std::size_t L> NISPS_FORCE_INLINE std::span<float> act_l() noexcept {
if constexpr (L == 0u) return a0_; else if constexpr (L == 1u) return a1_;
else if constexpr (L == 2u) return a2_; else return a3_;
}
template <std::size_t L> NISPS_FORCE_INLINE std::span<const float> act_l() const noexcept {
if constexpr (L == 0u) return a0_; else if constexpr (L == 1u) return a1_;
else if constexpr (L == 2u) return a2_; else return a3_;
}
template <std::size_t L> NISPS_FORCE_INLINE std::span<float> grad_w_l() noexcept {
if constexpr (L == 0u) return gw0_; else if constexpr (L == 1u) return gw1_;
else if constexpr (L == 2u) return gw2_; else return gw3_;
}
template <std::size_t L> NISPS_FORCE_INLINE std::span<float> grad_b_l() noexcept {
if constexpr (L == 0u) return gb0_; else if constexpr (L == 1u) return gb1_;
else if constexpr (L == 2u) return gb2_; else return gb3_;
}
// Backprop scratch (delta into layer L's input), sized fan_in(L).
template <std::size_t L> NISPS_FORCE_INLINE std::span<float> delta_l() noexcept {
if constexpr (L == 0u) return d0_; else if constexpr (L == 1u) return d1_;
else if constexpr (L == 2u) return d2_; else return d3_;
}
// Const-eval scratch (activation of layer L), sized fan_out(L). Mutable
// so `eval_loss() const` can run the shared forward code without touching
// the real activation caches.
template <std::size_t L> NISPS_FORCE_INLINE std::span<float> eval_act_l() const noexcept {
if constexpr (L == 0u) return e0_; else if constexpr (L == 1u) return e1_;
else if constexpr (L == 2u) return e2_; else return e3_;
}
// ---- global buffers ---------------------------------------------------
NISPS_FORCE_INLINE std::span<float> input_buf() noexcept { return input_; }
NISPS_FORCE_INLINE std::span<const float> input_buf() const noexcept { return input_; }
NISPS_FORCE_INLINE std::span<float> output_buf() noexcept { return output_; }
NISPS_FORCE_INLINE std::span<const float> output_buf() const noexcept { return output_; }
NISPS_FORCE_INLINE std::span<float> ds_features() noexcept { return dsf_; }
NISPS_FORCE_INLINE std::span<const float> ds_features() const noexcept { return dsf_; }
NISPS_FORCE_INLINE std::span<float> ds_labels() noexcept { return dsl_; }
NISPS_FORCE_INLINE std::span<const float> ds_labels() const noexcept { return dsl_; }
NISPS_FORCE_INLINE std::span<float> flat_buf() noexcept { return flat_; }
NISPS_FORCE_INLINE std::span<float> loss_hist_buf() noexcept { return lh_; }
NISPS_FORCE_INLINE std::span<const float> loss_hist_buf() const noexcept { return lh_; }
// Copies the live weights+biases directly into `dst` in the same flat
// layout as MLPCore::get_weights() (weights layer-major, then biases
// layer-major) — but writes straight from the layer buffers, with no
// intermediate flat_/flat_buf() hop. `dst` must be at least
// weight_count() long. Lets a caller that only needs a transient copy
// (feedback.hpp's snapshot/undo/nudge ops) take a single copy instead of
// double-copying through get_weights()'s scratch buffer.
void copy_weights_to(std::span<float> dst) const noexcept {
std::size_t k = 0u;
for (float v : weights_l<0u>()) dst[k++] = v;
for (float v : weights_l<1u>()) dst[k++] = v;
for (float v : weights_l<2u>()) dst[k++] = v;
for (float v : weights_l<3u>()) dst[k++] = v;
for (float v : biases_l<0u>()) dst[k++] = v;
for (float v : biases_l<1u>()) dst[k++] = v;
for (float v : biases_l<2u>()) dst[k++] = v;
for (float v : biases_l<3u>()) dst[k++] = v;
}
private:
std::array<float, NIn * NHidden1> w0_{};
std::array<float, NHidden1 * NHidden2> w1_{};
std::array<float, NHidden2 * NHidden3> w2_{};
std::array<float, NHidden3 * NOut> w3_{};
std::array<float, NHidden1> b0_{};
std::array<float, NHidden2> b1_{};
std::array<float, NHidden3> b2_{};
std::array<float, NOut> b3_{};
std::array<float, NHidden1> pa0_{};
std::array<float, NHidden2> pa1_{};
std::array<float, NHidden3> pa2_{};
std::array<float, NOut> pa3_{};
std::array<float, NHidden1> a0_{};
std::array<float, NHidden2> a1_{};
std::array<float, NHidden3> a2_{};
std::array<float, NOut> a3_{};
std::array<float, NIn * NHidden1> gw0_{};
std::array<float, NHidden1 * NHidden2> gw1_{};
std::array<float, NHidden2 * NHidden3> gw2_{};
std::array<float, NHidden3 * NOut> gw3_{};
std::array<float, NHidden1> gb0_{};
std::array<float, NHidden2> gb1_{};
std::array<float, NHidden3> gb2_{};
std::array<float, NOut> gb3_{};
std::array<float, NIn> d0_{};
std::array<float, NHidden1> d1_{};
std::array<float, NHidden2> d2_{};
std::array<float, NHidden3> d3_{};
mutable std::array<float, NHidden1> e0_{};
mutable std::array<float, NHidden2> e1_{};
mutable std::array<float, NHidden3> e2_{};
mutable std::array<float, NOut> e3_{};
std::array<float, NIn> input_{};
std::array<float, NOut> output_{};
std::array<float, NMaxExamples * NIn> dsf_{};
std::array<float, NMaxExamples * NOut> dsl_{};
std::array<float, weight_count()> flat_{};
std::array<float, NMaxIterTrain> lh_{};
};
} // namespace nisps::ml