Establish native micro runtime checkpoint

6 files changed, 1186 insertions, 0 deletions

diff --git a/research/experiments/001-checkpoint-granularity/README.md b/research/experiments/001-checkpoint-granularity/README.md
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+# Experiment 001: checkpoint granularity
+
+This is a native measurement apparatus for one known space/time tradeoff. It is
+not a new algorithm, a general dependency-graph runtime, or the product's language
+choice. The apparatus uses C17 and Python's standard library so it can be run
+with the tools present on the initial Linux host and with a C compiler on macOS.
+
+## Question and pre-measurement expectations
+
+How much does storing intermediate results at different intervals save, once the
+editable program and scheduling state are included? How much extra work does it
+cause when a rule changes?
+
+Expected, not measured at the time of writing this section:
+
+- Uniformly spaced checkpoints shrink the result cache at the cost of starting
+  recomputation before the changed instruction.
+- Root input changes offer no prefix to reuse. Fine checkpoints may only add
+  cache writes and comparisons in this workload.
+- Edits near the end favor fine checkpoints. This deliberately favorable case
+  must not stand in for all edits.
+- The editable model stays resident, so shrinking the cache 16-fold will not
+  shrink total core storage 16-fold.
+
+## Semantics and comparison
+
+The model consists of independent, statically connected chains. Each instruction
+is an 8-byte record with a scalar operator and parameter. Values are uint64_t;
+overflow wraps. Supported operators are add, XOR, multiply, and rotate/XOR.
+Only the final result of each chain is observed.
+
+One update applies a batch of changes, then computes all affected observed
+outputs. Changes alter roots, operators, and parameters, not graph topology.
+There is no renderer, effectful I/O, concurrent execution, or state migration.
+
+- Block 1 stores every intermediate result (fine incremental baseline).
+- Blocks 4, 16, and 64 store results at block ends.
+- A block equal to chain length recomputes the whole affected chain, retaining
+  only its final output (full recomputation baseline).
+
+All variants share program representation, input handling and per-chain dirty
+ranges. Unaffected chains are skipped by every variant. Fine and full variants
+use dedicated loops. Fine/block variants stop at an unchanged cached boundary
+only after passing the last changed instruction in the batch.
+
+The chain structure makes dependency information implicit. No general graph
+edge storage or graph partitioning is needed. This is an optimistic case for
+compact checkpoints; it cannot establish results for arbitrary graphs.
+
+For G chains of length L and checkpoint spacing B, the requested persistent
+storage in this implementation is:
+
+```text
+sizeof(Engine) + 8*G*L + 16*G + 8*G*ceil(L/B)
+                 model   inputs+   cached values,
+                         dirty    including outputs
+```
+
+This includes all live core arrays and the engine descriptor, but not allocator
+bookkeeping, stack, executable code, trace storage or OS pages. Trace size is
+recorded separately. It is not RSS, physical footprint, or total application RAM.
+There are no allocations in the timed update path.
+
+## Workloads
+
+The fixed initial matrix uses 16 chains, lengths 256 and 1024, and 256 updates per
+trace. Workload seed: 20260922.
+
+- `roots`: every chain's input changes on every update.
+- `uniform`: one uniformly selected instruction changes per update.
+- `tail`: one instruction in the last eight positions changes per update.
+- `dense`: eight instruction edits per chain per update, with replacement.
+
+Changes are XOR deltas so repeated traces continue changing the model. Two
+warm-up passes precede timing. Even measured replay counts leave identical final
+models across strategies; the runner checks their output checksums. Differential
+tests additionally compare every output after every update against independent
+from-scratch evaluation across multiple seeds, odd sizes and edge cases.
+
+## Reproduce
+
+From this directory, with Python 3 and a C compiler with ASan/UBSan support:
+
+```sh
+python3 run.py --check-only
+python3 run.py --output results/local-run
+```
+
+The runner refuses to overwrite an existing result directory. `CC` can select a
+compiler, such as `CC=clang`. It builds into a temporary directory. On Linux it
+pins itself and child processes to one available CPU and records that choice.
+
+Default measurements use seven trials with randomized strategy order within
+each trial. Pilot timings choose an even replay count per case, targeting 20 ms
+per measurement. All raw samples, memory counts, instruction counts, compiler
+flags, source hashes and host metadata are retained. Timing excludes program
+creation, trace creation, warm-up, and output verification. It includes change
+application, scheduling and recomputation.
+
+`median_ns_per_tick` is the median of batch-average processing times. It is not a
+P50/P99 input-to-display latency measurement. A shared host without controlled
+power or temperature permits preliminary comparisons, not hardware guarantees.
+
+The reported storage reduction is largely predicted by the formula. The useful
+observations are the whole-core reduction, processing cost and losing workloads.
+This experiment cannot establish automatic policy quality, novel research,
+editor usability, M3 performance, or universal memory savings.
+
+The first run and its interpretation are available in the
+[Korean research report](../../../docs/research/002-checkpoint-results.md).
diff --git a/research/experiments/001-checkpoint-granularity/benchmark.c b/research/experiments/001-checkpoint-granularity/benchmark.c
new file mode 100644
index 0000000..1c3f98b
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+++ b/research/experiments/001-checkpoint-granularity/benchmark.c
@@ -0,0 +1,276 @@
+#define _POSIX_C_SOURCE 200809L
+#include <errno.h>
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+/* Experimental apparatus, not the Pure runtime. All arithmetic is modulo 2^64. */
+typedef struct { uint32_t salt, control; } Op;
+typedef struct {
+    uint32_t chain, index;
+    uint64_t mask;
+} Change;
+typedef struct {
+    uint32_t chains, length, block, slots;
+    Op *ops;
+    uint64_t *inputs, *cache;
+    uint32_t *first, *last;
+} Engine;
+typedef struct {
+    uint32_t ticks, per_tick;
+    Change *changes;
+} Trace;
+
+static void die(const char *s) { fprintf(stderr, "%s\n", s); exit(1); }
+static void require(int condition, const char *s) { if (!condition) die(s); }
+static void *allocate(size_t count, size_t size) {
+    if (size && count > SIZE_MAX / size) die("allocation size overflow");
+    void *p = calloc(count, size);
+    if (!p) die("allocation failed");
+    return p;
+}
+static uint64_t random64(uint64_t *s) {
+    uint64_t z = (*s += UINT64_C(0x9e3779b97f4a7c15));
+    z = (z ^ (z >> 30)) * UINT64_C(0xbf58476d1ce4e5b9);
+    z = (z ^ (z >> 27)) * UINT64_C(0x94d049bb133111eb);
+    return z ^ (z >> 31);
+}
+static uint64_t rotate(uint64_t x, uint32_t n) {
+    return (x << n) | (x >> (64 - n));
+}
+static uint64_t evaluate(Op op, uint64_t x) {
+    switch (op.control & 3u) {
+    case 0: return x + op.salt;
+    case 1: return x ^ ((uint64_t)op.salt << 17);
+    case 2: return x * ((uint64_t)op.salt | 1u);
+    default: return rotate(x, 1u + ((op.control >> 2) % 63u)) ^ op.salt;
+    }
+}
+static uint64_t now_ns(void) {
+    struct timespec t;
+    if (clock_gettime(CLOCK_MONOTONIC, &t)) die("clock_gettime failed");
+    return (uint64_t)t.tv_sec * UINT64_C(1000000000) + (uint64_t)t.tv_nsec;
+}
+static uint64_t output(const Engine *e, uint32_t c) {
+    return e->cache[(size_t)c * e->slots + e->slots - 1];
+}
+static uint64_t reference_output(const Engine *e, uint32_t c) {
+    uint64_t x = e->inputs[c];
+    for (uint32_t n = 0; n < e->length; ++n)
+        x = evaluate(e->ops[(size_t)c * e->length + n], x);
+    return x;
+}
+static Engine create_engine(uint32_t chains, uint32_t length,
+                            uint32_t block, uint64_t seed) {
+    Engine e = { .chains = chains, .length = length, .block = block,
+                 .slots = (length + block - 1) / block };
+    e.ops = allocate((size_t)chains * length, sizeof(*e.ops));
+    e.inputs = allocate(chains, sizeof(*e.inputs));
+    e.cache = allocate((size_t)chains * e.slots, sizeof(*e.cache));
+    e.first = allocate(chains, sizeof(*e.first));
+    e.last = allocate(chains, sizeof(*e.last));
+    for (uint32_t c = 0; c < chains; ++c) {
+        e.inputs[c] = random64(&seed);
+        uint64_t x = e.inputs[c];
+        for (uint32_t n = 0; n < length; ++n) {
+            Op *op = &e.ops[(size_t)c * length + n];
+            op->salt = (uint32_t)random64(&seed);
+            op->control = (uint32_t)random64(&seed);
+            x = evaluate(*op, x);
+            if ((n + 1) % block == 0 || n + 1 == length)
+                e.cache[(size_t)c * e.slots + n / block] = x;
+        }
+        e.first[c] = length;
+    }
+    return e;
+}
+static void destroy_engine(Engine *e) {
+    free(e->ops); free(e->inputs); free(e->cache);
+    free(e->first); free(e->last);
+}
+static void apply(Engine *e, Change change) {
+    uint32_t c = change.chain, n = change.index;
+    require(c < e->chains && n <= e->length, "invalid change");
+    if (!change.mask) return;
+    if (n == e->length) {
+        e->inputs[c] ^= change.mask;
+        n = 0;
+    } else {
+        Op *op = &e->ops[(size_t)c * e->length + n];
+        op->salt ^= (uint32_t)change.mask;
+        op->control ^= (uint32_t)(change.mask >> 32);
+    }
+    if (n < e->first[c]) e->first[c] = n;
+    if (n > e->last[c]) e->last[c] = n;
+}
+static uint64_t update(Engine *e) {
+    uint64_t work = 0;
+    for (uint32_t c = 0; c < e->chains; ++c) {
+        uint32_t first = e->first[c], last = e->last[c];
+        if (first == e->length) continue;
+        const Op *ops = e->ops + (size_t)c * e->length;
+        uint64_t *cache = e->cache + (size_t)c * e->slots;
+        /* Full and fine have dedicated loops: no block-loop penalty for B=1. */
+        if (e->block == e->length) {
+            uint64_t x = e->inputs[c];
+            for (uint32_t n = 0; n < e->length; ++n) x = evaluate(ops[n], x);
+            cache[0] = x;
+            work += e->length;
+        } else if (e->block == 1) {
+            uint64_t x = first ? cache[first - 1] : e->inputs[c];
+            uint32_t n = first;
+            while (n < e->length) {
+                uint64_t old = cache[n];
+                cache[n] = x = evaluate(ops[n], x);
+                ++n;
+                /* Do not skip a later edit in the same batch. */
+                if (n > last && x == old) break;
+            }
+            work += n - first;
+        } else {
+            uint32_t start = first / e->block;
+            uint64_t x = start ? cache[start - 1] : e->inputs[c];
+            for (uint32_t b = start; b < e->slots; ++b) {
+                uint32_t begin = b * e->block, end = begin + e->block;
+                if (end > e->length) end = e->length;
+                for (uint32_t n = begin; n < end; ++n) x = evaluate(ops[n], x);
+                uint64_t old = cache[b];
+                cache[b] = x;
+                work += end - begin;
+                if (end > last && x == old) break;
+            }
+        }
+        e->first[c] = e->length;
+        e->last[c] = 0;
+    }
+    return work;
+}
+static uint64_t checksum(const Engine *e) {
+    uint64_t h = UINT64_C(0xcbf29ce484222325);
+    for (uint32_t c = 0; c < e->chains; ++c)
+        h = (h ^ output(e, c)) * UINT64_C(0x100000001b3);
+    return h;
+}
+static Trace create_trace(const char *kind, uint32_t chains, uint32_t length,
+                          uint32_t ticks, uint64_t seed) {
+    uint32_t per_tick = 1;
+    int roots = !strcmp(kind, "roots");
+    int dense = !strcmp(kind, "dense");
+    int uniform = !strcmp(kind, "uniform");
+    int tail = !strcmp(kind, "tail");
+    require(roots || dense || uniform || tail, "unknown workload");
+    if (roots) per_tick = chains;
+    if (dense) per_tick = chains * 8;
+    Trace t = { .ticks = ticks, .per_tick = per_tick };
+    t.changes = allocate((size_t)ticks * per_tick, sizeof(*t.changes));
+    for (uint32_t i = 0; i < ticks; ++i) {
+        for (uint32_t k = 0; k < per_tick; ++k) {
+            Change *p = &t.changes[(size_t)i * per_tick + k];
+            p->chain = roots ? k : dense ? k / 8 : (uint32_t)(random64(&seed) % chains);
+            p->index = roots ? length : (uint32_t)(random64(&seed) % length);
+            if (tail) {
+                uint32_t width = length < 8 ? length : 8;
+                p->index = length - width + p->index % width;
+            }
+            /* XOR changes keep every replay active; fixed assignments would not. */
+            p->mask = random64(&seed) | 1u;
+        }
+    }
+    return t;
+}
+static uint64_t replay(Engine *e, const Trace *t) {
+    uint64_t work = 0;
+    for (uint32_t i = 0; i < t->ticks; ++i) {
+        for (uint32_t k = 0; k < t->per_tick; ++k)
+            apply(e, t->changes[(size_t)i * t->per_tick + k]);
+        work += update(e);
+    }
+    return work;
+}
+static size_t owned_bytes(const Engine *e) {
+    return sizeof(*e) + (size_t)e->chains * e->length * sizeof(*e->ops)
+        + (size_t)e->chains * (sizeof(*e->inputs) + sizeof(*e->first) + sizeof(*e->last))
+        + (size_t)e->chains * e->slots * sizeof(*e->cache);
+}
+static void check_outputs(const Engine *e) {
+    for (uint32_t c = 0; c < e->chains; ++c)
+        require(output(e, c) == reference_output(e, c), "output disagrees with full reference");
+}
+static void self_test(void) {
+    const uint32_t lengths[] = {1, 2, 7, 17, 65, 257};
+    const uint32_t blocks[] = {1, 2, 4, 16, 64, 256};
+    uint64_t checked_ticks = 0;
+    for (uint64_t seed = 1; seed <= 8; ++seed) {
+        for (size_t l = 0; l < sizeof(lengths) / sizeof(*lengths); ++l) {
+            uint32_t length = lengths[l];
+            for (size_t b = 0; b <= sizeof(blocks) / sizeof(*blocks); ++b) {
+                uint32_t block = b == sizeof(blocks) / sizeof(*blocks) ? length : blocks[b];
+                if (block > length) continue;
+                Engine e = create_engine(3, length, block, seed);
+                check_outputs(&e);
+                uint64_t rng = seed;
+                for (uint32_t tick = 0; tick < 500; ++tick) {
+                    uint32_t count = (uint32_t)(random64(&rng) % 9);
+                    for (uint32_t k = 0; k < count; ++k) {
+                        Change change = {
+                            .chain = (uint32_t)(random64(&rng) % e.chains),
+                            .index = (uint32_t)(random64(&rng) % (length + 1)),
+                            .mask = random64(&rng)
+                        };
+                        if (tick % 11 == 0) change.mask = 0;
+                        apply(&e, change);
+                        if (tick % 13 == 0) apply(&e, change); /* cancelling edits */
+                    }
+                    (void)update(&e);
+                    check_outputs(&e);
+                    require(update(&e) == 0, "clean update performed work");
+                    ++checked_ticks;
+                }
+                destroy_engine(&e);
+            }
+        }
+    }
+    /* An unchanged early checkpoint must not suppress a later dirty operation. */
+    for (uint32_t block = 1; block <= 4; block *= 2) {
+        Engine e = create_engine(1, 8, block, 77);
+        Change cancel = {0, 0, 123}, later = {0, 7, 987};
+        apply(&e, cancel); apply(&e, cancel); apply(&e, later);
+        (void)update(&e); check_outputs(&e); destroy_engine(&e);
+    }
+    printf("{\"checked_ticks\":%" PRIu64 ",\"status\":\"passed\"}\n", checked_ticks);
+}
+static uint32_t number(const char *s, uint32_t max) {
+    char *end;
+    errno = 0;
+    unsigned long n = strtoul(s, &end, 10);
+    if (errno || end == s || *end || !n || n > max) die("invalid positive integer");
+    return (uint32_t)n;
+}
+int main(int argc, char **argv) {
+    if (argc == 2 && !strcmp(argv[1], "--check")) { self_test(); return 0; }
+    if (argc != 8) die("usage: benchmark CHAINS LENGTH BLOCK WORKLOAD TICKS REPLAYS SEED | --check");
+    uint32_t chains = number(argv[1], 1024), length = number(argv[2], 65536);
+    uint32_t block = number(argv[3], length), ticks = number(argv[5], 4096);
+    uint32_t replays = number(argv[6], 4096), seed = number(argv[7], UINT32_MAX);
+    require((uint64_t)chains * length <= UINT64_C(1048576), "model too large for this lab");
+    Engine e = create_engine(chains, length, block, seed);
+    Trace t = create_trace(argv[4], chains, length, ticks, seed + UINT64_C(1234567));
+    (void)replay(&e, &t); (void)replay(&e, &t); /* two warm-up replays */
+    uint64_t work = 0, start = now_ns();
+    for (uint32_t r = 0; r < replays; ++r) work += replay(&e, &t);
+    uint64_t elapsed = now_ns() - start;
+    check_outputs(&e); /* correctness check is outside the measured interval */
+    printf("{\"elapsed_ns\":%" PRIu64 ",\"ticks\":%" PRIu64
+           ",\"node_evaluations\":%" PRIu64 ",\"core_owned_bytes\":%zu"
+           ",\"model_bytes\":%zu,\"cache_bytes\":%zu,\"engine_bytes\":%zu"
+           ",\"trace_bytes\":%zu,\"checksum\":\"%016" PRIx64 "\"}\n",
+           elapsed, (uint64_t)ticks * replays, work, owned_bytes(&e),
+           (size_t)chains * length * sizeof(Op),
+           (size_t)chains * e.slots * sizeof(uint64_t), sizeof(Engine),
+           sizeof(t) + (size_t)t.ticks * t.per_tick * sizeof(Change), checksum(&e));
+    free(t.changes); destroy_engine(&e);
+    return 0;
+}
diff --git a/research/experiments/001-checkpoint-granularity/results/2026-09-22-linux-aarch64/environment.json b/research/experiments/001-checkpoint-granularity/results/2026-09-22-linux-aarch64/environment.json
new file mode 100644
index 0000000..1e967ad
--- /dev/null
+++ b/research/experiments/001-checkpoint-granularity/results/2026-09-22-linux-aarch64/environment.json
@@ -0,0 +1,330 @@
+{
+  "started_utc": "2026-09-22T09:32:06.820074+00:00",
+  "platform": "Linux-6.18.39+rpt-rpi-2712-aarch64-with-glibc2.41",
+  "machine": "aarch64",
+  "compiler": "cc (Debian 14.2.0-19) 14.2.0\nCopyright (C) 2024 Free Software Foundation, Inc.\nThis is free software; see the source for copying conditions.  There is NO\nwarranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.",
+  "flags": [
+    "-std=c17",
+    "-O3",
+    "-Wall",
+    "-Wextra",
+    "-Wpedantic",
+    "-Werror"
+  ],
+  "python": "3.14.7",
+  "source_sha256": "9e1b1108f58a8725458531207bd1edf06d9af43ae3255c3b97d4388c2b58c707",
+  "runner_sha256": "4c3e8ae899eb5068813df9529a8c7953d63730ee3ca507a0a7dbe58963b1db01",
+  "trials": 7,
+  "target_ms": 20.0,
+  "seed": 20260922,
+  "timing": "batch elapsed time / update ticks; not input latency",
+  "memory": "sizeof engine + requested live array bytes; excludes allocator, harness, code, OS",
+  "power_control": "not controlled; shared host; preliminary measurements",
+  "original_affinity": [
+    0,
+    1,
+    2,
+    3
+  ],
+  "measurement_affinity": [
+    0
+  ],
+  "cpu_description": [
+    "CPU architecture: 8",
+    "CPU implementer\t: 0x41",
+    "CPU part\t: 0xd0b",
+    "Model\t\t: Raspberry Pi 5 Model B Rev 1.1"
+  ],
+  "release_check": {
+    "checked_ticks": 108000,
+    "status": "passed"
+  },
+  "sanitizer_check": {
+    "checked_ticks": 108000,
+    "status": "passed"
+  },
+  "calibration_replays": [
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "roots",
+      "block": 1,
+      "replays": 6
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "roots",
+      "block": 4,
+      "replays": 4
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "roots",
+      "block": 16,
+      "replays": 6
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "roots",
+      "block": 64,
+      "replays": 6
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "roots",
+      "block": 256,
+      "replays": 6
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "uniform",
+      "block": 1,
+      "replays": 130
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "uniform",
+      "block": 4,
+      "replays": 110
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "uniform",
+      "block": 16,
+      "replays": 130
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "uniform",
+      "block": 64,
+      "replays": 124
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "uniform",
+      "block": 256,
+      "replays": 74
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "tail",
+      "block": 1,
+      "replays": 968
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "tail",
+      "block": 4,
+      "replays": 870
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "tail",
+      "block": 16,
+      "replays": 730
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "tail",
+      "block": 64,
+      "replays": 384
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "tail",
+      "block": 256,
+      "replays": 86
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "dense",
+      "block": 1,
+      "replays": 4
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "dense",
+      "block": 4,
+      "replays": 4
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "dense",
+      "block": 16,
+      "replays": 4
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "dense",
+      "block": 64,
+      "replays": 4
+    },
+    {
+      "chains": 16,
+      "length": 256,
+      "workload": "dense",
+      "block": 256,
+      "replays": 4
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diff --git a/research/experiments/001-checkpoint-granularity/results/2026-09-22-linux-aarch64/raw.csv b/research/experiments/001-checkpoint-granularity/results/2026-09-22-linux-aarch64/raw.csv
new file mode 100644
index 0000000..1ed88ef
--- /dev/null
+++ b/research/experiments/001-checkpoint-granularity/results/2026-09-22-linux-aarch64/raw.csv
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+5,16,256,roots,64,6,24760574,1536,6291456,33592,32768,512,56,65552,07e316e8e83163f0,16120.165364583334,4096.0

+5,16,1024,uniform,16,24,20702411,6144,3323520,139576,131072,8192,56,4112,cc440e349b9b5a57,3369.5330403645835,540.9375

+5,16,256,tail,16,730,15642655,186880,2990080,35128,32768,2048,56,4112,07e316e8e83163f0,83.70427547089041,16.0

+5,16,1024,roots,1,2,58483900,512,8388608,262456,131072,131072,56,65552,cc440e349b9b5a57,114226.3671875,16384.0

+5,16,1024,roots,64,2,54285033,512,8388608,133432,131072,2048,56,65552,cc440e349b9b5a57,106025.455078125,16384.0

+5,16,256,tail,64,384,18131930,98304,6291456,33592,32768,512,56,4112,07e316e8e83163f0,184.4475301106771,64.0

+5,16,1024,uniform,1024,14,22782001,3584,3670016,131512,131072,128,56,4112,cc440e349b9b5a57,6356.585100446428,1024.0

+5,16,1024,roots,4,2,70559817,512,8388608,164152,131072,32768,56,65552,cc440e349b9b5a57,137812.142578125,16384.0

+5,16,1024,uniform,64,24,20210762,6144,3472896,133432,131072,2048,56,4112,cc440e349b9b5a57,3289.5120442708335,565.25

+5,16,256,roots,16,6,25681295,1536,6291456,35128,32768,2048,56,65552,07e316e8e83163f0,16719.593098958332,4096.0

+5,16,1024,dense,64,2,55456236,512,7682176,133432,131072,2048,56,524304,cc440e349b9b5a57,108312.9609375,15004.25

+6,16,1024,roots,1024,2,54870791,512,8388608,131512,131072,128,56,65552,cc440e349b9b5a57,107169.513671875,16384.0

+6,16,1024,uniform,16,24,20742114,6144,3323520,139576,131072,8192,56,4112,cc440e349b9b5a57,3375.9951171875,540.9375

+6,16,256,tail,16,730,15687340,186880,2990080,35128,32768,2048,56,4112,07e316e8e83163f0,83.94338613013699,16.0

+6,16,1024,dense,1024,2,59332807,512,8388608,131512,131072,128,56,524304,cc440e349b9b5a57,115884.388671875,16384.0

+6,16,1024,uniform,64,24,20222374,6144,3472896,133432,131072,2048,56,4112,cc440e349b9b5a57,3291.4020182291665,565.25

+6,16,1024,roots,1,2,58901437,512,8388608,262456,131072,131072,56,65552,cc440e349b9b5a57,115041.869140625,16384.0

+6,16,1024,tail,64,384,18025357,98304,6291456,133432,131072,2048,56,4112,cc440e349b9b5a57,183.36341349283853,64.0

+6,16,256,roots,256,6,25008240,1536,6291456,33208,32768,128,56,65552,07e316e8e83163f0,16281.40625,4096.0

+6,16,1024,dense,4,2,63551748,512,7458720,164152,131072,32768,56,524304,cc440e349b9b5a57,124124.5078125,14567.8125

+6,16,1024,roots,64,2,56267698,512,8388608,133432,131072,2048,56,65552,cc440e349b9b5a57,109897.84765625,16384.0

+6,16,256,tail,256,86,18806949,22016,5636096,33208,32768,128,56,4112,07e316e8e83163f0,854.2400526889535,256.0

+6,16,1024,roots,4,2,68814522,512,8388608,164152,131072,32768,56,65552,cc440e349b9b5a57,134403.36328125,16384.0

+6,16,256,dense,256,4,27934608,1024,4194304,33208,32768,128,56,524304,07e316e8e83163f0,27279.890625,4096.0

+6,16,256,tail,4,870,15578303,222720,1332840,41272,32768,8192,56,4112,07e316e8e83163f0,69.94568516522989,5.984375

+6,16,256,dense,4,4,28803219,1024,3753408,41272,32768,8192,56,524304,07e316e8e83163f0,28128.1435546875,3665.4375

+6,16,1024,uniform,4,22,21089521,5632,3014264,164152,131072,32768,56,4112,cc440e349b9b5a57,3744.5882457386365,535.203125

+6,16,1024,tail,4,834,14739063,213504,1277688,164152,131072,32768,56,4112,cc440e349b9b5a57,69.03413050809353,5.984375

+6,16,1024,uniform,1,24,20910965,6144,3279504,262456,131072,131072,56,4112,cc440e349b9b5a57,3403.4773763020835,533.7734375

+6,16,256,roots,4,4,22458464,1024,4194304,41272,32768,8192,56,65552,07e316e8e83163f0,21932.09375,4096.0

+6,16,1024,dense,1,2,56255976,512,7446690,262456,131072,131072,56,524304,cc440e349b9b5a57,109874.953125,14544.31640625

+6,16,256,tail,64,384,18071820,98304,6291456,33592,32768,512,56,4112,07e316e8e83163f0,183.8360595703125,64.0

+6,16,256,tail,1,968,15814117,247808,1128688,65848,32768,32768,56,4112,07e316e8e83163f0,63.81600674715909,4.5546875

+6,16,1024,roots,16,2,57245493,512,8388608,139576,131072,8192,56,65552,cc440e349b9b5a57,111807.603515625,16384.0

+6,16,1024,dense,16,2,57808882,512,7506624,139576,131072,8192,56,524304,cc440e349b9b5a57,112907.97265625,14661.375

+6,16,256,roots,64,6,25547351,1536,6291456,33592,32768,512,56,65552,07e316e8e83163f0,16632.389973958332,4096.0

+6,16,1024,tail,16,708,15922932,181248,2899968,139576,131072,8192,56,4112,cc440e349b9b5a57,87.85162870762711,16.0

+6,16,256,dense,64,4,27213979,1024,4080128,33592,32768,512,56,524304,07e316e8e83163f0,26576.1513671875,3984.5

+6,16,256,uniform,256,74,19487226,18944,4849664,33208,32768,128,56,4112,07e316e8e83163f0,1028.6753589527027,256.0

+6,16,1024,tail,1,912,16061655,233472,1063392,262456,131072,131072,56,4112,cc440e349b9b5a57,68.79478053042763,4.5546875

+6,16,1024,dense,64,2,55728624,512,7682176,133432,131072,2048,56,524304,cc440e349b9b5a57,108844.96875,15004.25

+6,16,256,uniform,4,110,17905042,28160,3722840,41272,32768,8192,56,4112,07e316e8e83163f0,635.8324573863637,132.203125

+6,16,256,dense,16,4,27274238,1024,3842048,35128,32768,2048,56,524304,07e316e8e83163f0,26634.998046875,3752.0

+6,16,256,uniform,1,130,18982300,33280,4352140,65848,32768,32768,56,4112,07e316e8e83163f0,570.3816105769231,130.7734375

+6,16,256,uniform,64,124,19114171,31744,5150464,33592,32768,512,56,4112,07e316e8e83163f0,602.1349231350806,162.25

+6,16,256,roots,1,6,29285699,1536,6291456,65848,32768,32768,56,65552,07e316e8e83163f0,19066.210286458332,4096.0

+6,16,256,dense,1,4,26745535,1024,3729584,65848,32768,32768,56,524304,07e316e8e83163f0,26118.6865234375,3642.171875

+6,16,256,uniform,16,130,18815023,33280,4590560,35128,32768,2048,56,4112,07e316e8e83163f0,565.3552584134616,137.9375

+6,16,256,roots,16,6,24256649,1536,6291456,35128,32768,2048,56,65552,07e316e8e83163f0,15792.089192708334,4096.0

+6,16,1024,uniform,1024,14,22782186,3584,3670016,131512,131072,128,56,4112,cc440e349b9b5a57,6356.63671875,1024.0

+6,16,1024,tail,1024,14,22543335,3584,3670016,131512,131072,128,56,4112,cc440e349b9b5a57,6289.993024553572,1024.0

diff --git a/research/experiments/001-checkpoint-granularity/results/2026-09-22-linux-aarch64/summary.csv b/research/experiments/001-checkpoint-granularity/results/2026-09-22-linux-aarch64/summary.csv
new file mode 100644
index 0000000..861c9d1
--- /dev/null
+++ b/research/experiments/001-checkpoint-granularity/results/2026-09-22-linux-aarch64/summary.csv
@@ -0,0 +1,41 @@
+chains,length,workload,block,median_ns_per_tick,min_ns_per_tick,max_ns_per_tick,core_owned_bytes,cache_bytes,evaluations_per_tick

+16,256,roots,1,18801.478515625,18084.694010416668,20032.295572916668,65848,32768,4096.0

+16,256,roots,4,21405.203125,20964.123046875,21932.09375,41272,8192,4096.0

+16,256,roots,16,16275.450520833334,15792.089192708334,16719.593098958332,35128,2048,4096.0

+16,256,roots,64,16120.165364583334,15248.650390625,16632.389973958332,33592,512,4096.0

+16,256,roots,256,16029.176432291666,14328.053385416666,16772.75,33208,128,4096.0

+16,256,uniform,1,574.3891526442308,570.3816105769231,576.8920372596153,65848,32768,130.7734375

+16,256,uniform,4,639.0146661931818,633.2309303977273,643.0563920454546,41272,8192,132.203125

+16,256,uniform,16,566.1882512019231,565.3552584134616,569.2787560096153,35128,2048,137.9375

+16,256,uniform,64,602.1349231350806,600.8625882056451,608.9107547883065,33592,512,162.25

+16,256,uniform,256,1020.9371304898649,1016.9566089527027,1032.8142419763512,33208,128,256.0

+16,256,tail,1,65.4934586454029,63.60011783316116,66.48152602014463,65848,32768,4.5546875

+16,256,tail,4,69.92689475574713,68.2047503591954,70.07431303879311,41272,8192,5.984375

+16,256,tail,16,83.94338613013699,83.27748287671233,85.78413420376712,35128,2048,16.0

+16,256,tail,64,184.586181640625,183.8360595703125,187.7897745768229,33592,512,64.0

+16,256,tail,256,856.3967114825581,850.7249273255813,869.8936228197674,33208,128,256.0

+16,256,dense,1,26021.880859375,25990.79296875,26118.6865234375,65848,32768,3642.171875

+16,256,dense,4,28089.0634765625,28053.1826171875,28375.2861328125,41272,8192,3665.4375

+16,256,dense,16,26632.0869140625,26573.638671875,26737.646484375,35128,2048,3752.0

+16,256,dense,64,26451.279296875,26394.7822265625,26613.9482421875,33592,512,3984.5

+16,256,dense,256,27236.0361328125,27165.814453125,27286.9072265625,33208,128,4096.0

+16,1024,roots,1,115259.642578125,114226.3671875,118340.623046875,262456,131072,16384.0

+16,1024,roots,4,136649.09375,127162.556640625,137812.142578125,164152,32768,16384.0

+16,1024,roots,16,112929.783203125,111807.603515625,114537.05859375,139576,8192,16384.0

+16,1024,roots,64,106209.98828125,105137.505859375,109897.84765625,133432,2048,16384.0

+16,1024,roots,1024,107713.3515625,106359.80078125,110034.27734375,131512,128,16384.0

+16,1024,uniform,1,3401.421875,3389.2872721354165,3461.4049479166665,262456,131072,533.7734375

+16,1024,uniform,4,3757.201349431818,3744.5882457386365,3956.7652698863635,164152,32768,535.203125

+16,1024,uniform,16,3374.51513671875,3358.8570963541665,3733.6276041666665,139576,8192,540.9375

+16,1024,uniform,64,3289.5120442708335,3284.544921875,3313.1031901041665,133432,2048,565.25

+16,1024,uniform,1024,6338.660714285715,6323.904017857143,6481.678013392857,131512,128,1024.0

+16,1024,tail,1,67.02987938596492,64.57602196408992,68.94516687225877,262456,131072,4.5546875

+16,1024,tail,4,69.63277971372902,68.53097365857315,70.94154676258992,164152,32768,5.984375

+16,1024,tail,16,88.98257635946328,86.80436197916667,89.67877714512711,139576,8192,16.0

+16,1024,tail,64,184.76985677083334,183.36341349283853,193.45831298828125,133432,2048,64.0

+16,1024,tail,1024,6295.3046875,6281.147042410715,7935.422154017857,131512,128,1024.0

+16,1024,dense,1,110093.990234375,109599.8515625,115644.2265625,262456,131072,14544.31640625

+16,1024,dense,4,123794.791015625,123565.841796875,124339.0625,164152,32768,14567.8125

+16,1024,dense,16,113425.875,111541.220703125,115264.88671875,139576,8192,14661.375

+16,1024,dense,64,108271.22265625,107769.125,108844.96875,133432,2048,15004.25

+16,1024,dense,1024,115971.736328125,115884.388671875,117461.318359375,131512,128,16384.0

diff --git a/research/experiments/001-checkpoint-granularity/run.py b/research/experiments/001-checkpoint-granularity/run.py
new file mode 100644
index 0000000..b2d66f2
--- /dev/null
+++ b/research/experiments/001-checkpoint-granularity/run.py
@@ -0,0 +1,148 @@
+#!/usr/bin/env python3
+"""Build, check, measure, and preserve raw data using only the Python stdlib."""
+import argparse
+import csv
+import hashlib
+import json
+import math
+import os
+from pathlib import Path
+import platform
+import random
+import shlex
+import statistics
+import subprocess
+import tempfile
+from datetime import datetime, timezone
+
+
+ROOT = Path(__file__).resolve().parent
+SOURCE = ROOT / "benchmark.c"
+FLAGS = ["-std=c17", "-O3", "-Wall", "-Wextra", "-Wpedantic", "-Werror"]
+
+
+def command(args):
+    return subprocess.check_output(args, text=True).strip()
+
+
+def write_csv(path, rows):
+    with path.open("w", newline="") as f:
+        writer = csv.DictWriter(f, fieldnames=list(rows[0]))
+        writer.writeheader()
+        writer.writerows(rows)
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--output", type=Path)
+    parser.add_argument("--trials", type=int, default=7)
+    parser.add_argument("--target-ms", type=float, default=20.0)
+    parser.add_argument("--check-only", action="store_true")
+    args = parser.parse_args()
+    if args.trials < 3 or not 1 <= args.target_ms <= 1000:
+        parser.error("use at least 3 trials and a target from 1 to 1000 ms")
+    if not args.check_only and args.output is None:
+        parser.error("--output is required for measurements")
+    cc = shlex.split(os.environ.get("CC", "cc"))
+    environment = {
+        "started_utc": datetime.now(timezone.utc).isoformat(),
+        "platform": platform.platform(), "machine": platform.machine(),
+        "compiler": command(cc + ["--version"]), "flags": FLAGS,
+        "python": platform.python_version(),
+        "source_sha256": hashlib.sha256(SOURCE.read_bytes()).hexdigest(),
+        "runner_sha256": hashlib.sha256(Path(__file__).read_bytes()).hexdigest(),
+        "trials": args.trials, "target_ms": args.target_ms,
+        "seed": 20260922, "timing": "batch elapsed time / update ticks; not input latency",
+        "memory": "sizeof engine + requested live array bytes; excludes allocator, harness, code, OS",
+        "power_control": "not controlled; shared host; preliminary measurements",
+    }
+    # One CPU reduces migration noise. This is recorded, not assumed to remove noise.
+    if hasattr(os, "sched_getaffinity"):
+        affinity = sorted(os.sched_getaffinity(0))
+        environment["original_affinity"] = affinity
+        os.sched_setaffinity(0, {affinity[0]})
+        environment["measurement_affinity"] = sorted(os.sched_getaffinity(0))
+    cpuinfo = Path("/proc/cpuinfo")
+    if cpuinfo.exists():
+        allowed = ("model name", "CPU implementer", "CPU architecture", "CPU part", "Model")
+        environment["cpu_description"] = sorted({
+            line for line in cpuinfo.read_text().splitlines()
+            if line.split(":", 1)[0].strip() in allowed
+        })
+    with tempfile.TemporaryDirectory(prefix="pure-checkpoints-") as tmp:
+        binary = Path(tmp) / "benchmark"
+        subprocess.run(cc + FLAGS + [str(SOURCE), "-o", str(binary)], check=True)
+        environment["release_check"] = json.loads(command([str(binary), "--check"]))
+        checked = Path(tmp) / "benchmark-checked"
+        check_flags = ["-std=c17", "-O1", "-g", "-Wall", "-Wextra", "-Wpedantic", "-Werror",
+                       "-fsanitize=address,undefined", "-fno-omit-frame-pointer"]
+        subprocess.run(cc + check_flags + [str(SOURCE), "-o", str(checked)], check=True)
+        environment["sanitizer_check"] = json.loads(command([str(checked), "--check"]))
+        print("Differential checks passed in release and ASan/UBSan builds.", flush=True)
+        if args.check_only:
+            print(json.dumps(environment, indent=2))
+            return
+        # Fail before measurements if a previous run would be overwritten.
+        args.output.mkdir(parents=True, exist_ok=False)
+
+        cases = []
+        for chains, length in [(16, 256), (16, 1024)]:
+            for workload in ["roots", "uniform", "tail", "dense"]:
+                for block in [1, 4, 16, 64, length]:
+                    cases.append((chains, length, workload, block))
+
+        def sample(case, replays):
+            chains, length, workload, block = case
+            return json.loads(command([str(binary), str(chains), str(length), str(block),
+                                       workload, "256", str(replays), str(environment["seed"])]))
+
+        calibration = {}
+        for case in cases:
+            pilot = sample(case, 2)
+            wanted = math.ceil(2 * args.target_ms * 1e6 / max(1, pilot["elapsed_ns"]))
+            # Even replay counts leave the same final model in every strategy.
+            calibration[case] = min(2048, max(2, wanted + wanted % 2))
+        environment["calibration_replays"] = [
+            {"chains": c[0], "length": c[1], "workload": c[2], "block": c[3], "replays": r}
+            for c, r in calibration.items()
+        ]
+        rows = []
+        checksums = {}
+        rng = random.Random(81173)
+        for trial in range(args.trials):
+            order = cases.copy()
+            rng.shuffle(order)
+            for case in order:
+                result = sample(case, calibration[case])
+                chains, length, workload, block = case
+                key = (chains, length, workload)
+                if checksums.setdefault(key, result["checksum"]) != result["checksum"]:
+                    raise RuntimeError(f"cross-strategy output mismatch: {case}")
+                row = {"trial": trial, "chains": chains, "length": length,
+                       "workload": workload, "block": block, "replays": calibration[case],
+                       **result}
+                row["ns_per_tick"] = result["elapsed_ns"] / result["ticks"]
+                row["evaluations_per_tick"] = result["node_evaluations"] / result["ticks"]
+                rows.append(row)
+            write_csv(args.output / "raw.csv", rows)
+            print(f"Completed trial {trial + 1}/{args.trials}.", flush=True)
+        summary = []
+        for case in cases:
+            chains, length, workload, block = case
+            group = [r for r in rows if (r["chains"], r["length"], r["workload"], r["block"]) == case]
+            times = [r["ns_per_tick"] for r in group]
+            summary.append({"chains": chains, "length": length, "workload": workload, "block": block,
+                            "median_ns_per_tick": statistics.median(times),
+                            "min_ns_per_tick": min(times), "max_ns_per_tick": max(times),
+                            "core_owned_bytes": group[0]["core_owned_bytes"],
+                            "cache_bytes": group[0]["cache_bytes"],
+                            "evaluations_per_tick": group[0]["evaluations_per_tick"]})
+        write_csv(args.output / "summary.csv", summary)
+        environment["completed_utc"] = datetime.now(timezone.utc).isoformat()
+        environment["binary_bytes"] = binary.stat().st_size
+        (args.output / "environment.json").write_text(json.dumps(environment, indent=2) + "\n")
+        print(f"Saved raw data, summary, and environment to {args.output}")
+
+
+if __name__ == "__main__":
+    main()