Megaminx Tpu Provision

Megaminx v6e TPU provision + setup + run

Project <GCP_PROJECT>. Artifacts staged in gs://<GCS_BUCKET> (edited kernel jax_beam_spmd_v_qshort.py, sym driver gcp_beam_v6e.py, jax_model.py, both models, rotations_720.npy, puzzle_info.json, test.csv, hashtest.py, vtest.py). See memory [[megaminx-v6e-beam-port]] + [[tpu-builders-program-gcp-setup]] for the full backstory.

Every gcloud compute ssh call must end with this filter (Windows plink noise): 2>&1 | grep -vE "host key|fingerprint|cache|trust|connecting|Return|guarantee|Store key|Warning|ssh-ed25519|troubleshoot"

1. Pick zone + machine type, check quota

• v6e hardware + CT6E quota=48 zones: europe-west4-a (capacity, but 8-chip backend-faults as of 2026-06), asia-northeast1-b, asia-east1-c, asia-southeast1-b, asia-south1-b. The program zones us-east5-a / us-central1-a have 0 CT6E quota (don't use).
• ct6e-standard-4t = 4 chips (reliable), ct6e-standard-8t = 8 chips (2x ranks → super-linearly faster wide beams, but GCP-blocked in europe as of 2026-06).
• Quota check: gcloud beta quotas info describe TPUS-PER-TPU-FAMILY-per-project-region --service=compute.googleapis.com --project=<GCP_PROJECT> --flatten="dimensionsInfos[]" --format="csv[no-heading](dimensionsInfos.dimensions.region,dimensionsInfos.dimensions.tpu_family,dimensionsInfos.details.value)" | grep CT6E

2. Match the BPTR field to the rank count (edit kernel before staging)

In jax_beam_spmd_v_qshort.py: 4 ranks → 25/2/5 (BPTR_PL_BITS=25, BPTR_RANK_BITS=2); 8 ranks → 24/3/5 (BPTR_PL_BITS=24, BPTR_RANK_BITS=3). Both give B_global ≤ 134M. Wrong rank bits = silent walkback corruption (the validation raises if world_size > 1<<BPTR_RANK_BITS). Re-stage after editing: gcloud storage cp <kernel> gs://<GCS_BUCKET>.

2b. For 8 chips: use the Queued Resources API, NOT instances create

Single-host ct6e-standard-8t FLEX_START via gcloud compute instances create is backend-broken: it reaches STAGING, grinds ~14 min, then fails INTERNAL_ERROR/503/BACKEND_ERROR and self-deletes with no retry (reproduced 3/3 across europe-west4-a + us-east5-a/b, 2026-06-11 — it's the 8-chip topology, not zone/quota). Use the Cloud TPU Queued Resources API instead — it queues + auto-retries the bring-up:

gcloud components install alpha --quiet   # one-time
gcloud alpha compute tpus queued-resources create mm-v6e8-qr --project=<GCP_PROJECT> \
  --zone=us-east5-a --accelerator-type=v6e-8 --runtime-version=v2-alpha-tpuv6e \
  --node-id=mm-v6e8 --provisioning-model=flex-start --max-run-duration=24h

Watch queued-resources describe mm-v6e8-qr --format="value(state.state)": WAITING_FOR_RESOURCES→PROVISIONING→ACTIVE (~5 min; came up HEALTHY in us-east5-a, CT6E quota now 16). This yields a TPU-VM — use gcloud compute tpus tpu-vm ssh/scp/describe, not gcloud compute instances. jax is NOT pre-installed on v2-alpha-tpuv6e (pip jax[tpu]). First tpu-vm ssh on Windows: pipe printf 'y\n' | to cache the plink host key. Teardown: gcloud alpha compute tpus queued-resources delete mm-v6e8-qr --zone=us-east5-a --force --quiet. (MIG flex-start resize-requests are GPU/H4D-only — no TPU; QR is the TPU equivalent.) The §3/4 machine-type path below stays correct for 1t/4t.

3. Provision (async) + watch

gcloud compute instances create mm-v6e-<tag> --project=<GCP_PROJECT> --zone=<ZONE> \
  --machine-type=<ct6e-standard-4t|8t> --provisioning-model=FLEX_START \
  --request-valid-for-duration=2h --max-run-duration=24h --instance-termination-action=DELETE \
  --maintenance-policy=TERMINATE --image-project=ubuntu-os-accelerator-images \
  --image-family=ubuntu-accel-2204-amd64-tpu-v5e-v5p-v6e --async

• --request-valid-for-duration MAX is 7200s (2h). --max-run-duration=24h auto-deletes (cost backstop). FLEX_START is $0 while PENDING.
• Watch in a run_in_background Bash loop polling gcloud compute instances describe ... --format="value(status)" every 30s. Status semantics: PENDING=queued for capacity; STAGING=booting; → RUNNING (success). STAGING→gone = INTERNAL_ERROR backend fault (check gcloud compute operations describe <op>); immediate "not found" / ZONE_RESOURCE_POOL_EXHAUSTED = stockout (try another zone). Record whether STAGING was reached to tell fault from stockout.

4. Setup (once RUNNING)

Data disk: v6e/ct6e rejects pd-* disks — must be hyperdisk. Either create+attach --type=hyperdisk-balanced and mkfs.ext4, or attach an existing one at create with --disk=name=...,auto-delete=no (survives the flex VM). Then, in ONE ssh (nohup the slow installs):

sudo mkdir -p /mnt/data && sudo mount -o discard,defaults /dev/disk/by-id/google-<devname> /mnt/data && sudo chmod -R a+rwx /mnt/data
sudo apt-get update -qq && sudo apt-get install -y -qq python3.10-venv python3-pip   # update BEFORE venv or ensurepip fails
python3 -m venv ~/tpu-env
~/tpu-env/bin/pip install -q -U pip 'jax[tpu]' -f https://storage.googleapis.com/jax-releases/libtpu_releases.html
~/tpu-env/bin/pip install -q torch --index-url https://download.pytorch.org/whl/cpu   # for load_params_from_pt
# glibc guard: this image family is Ubuntu 22.04 (glibc 2.34), so wheels run. On ANY older base
# (e.g. a shared 20.04 box, glibc 2.31) check `ldd --version` FIRST: torch_xla >=2.5 needs glibc
# 2.34, jaxlib only ~2.27 -> JAX installs+runs but modern torch_xla won't import. See [[tpu-v4-research-box]].
mkdir -p /mnt/data/v6e /mnt/data/trees /mnt/data/out
gcloud storage cp 'gs://<GCS_BUCKET>*' /mnt/data/v6e/
~/tpu-env/bin/python -c 'import jax,torch; print("dev",jax.device_count(),jax.devices()[0].device_kind)'   # expect 4 or 8, "TPU v6 lite"

Note: v6e exposes chips via vfio, so /dev/accel* is EMPTY — that's normal; trust jax.device_count().

5. Validate, then run

ALWAYS run the two diagnostics first (catches config-gap-vs-real-bug in minutes): ~/tpu-env/bin/python /mnt/data/v6e/hashtest.py (host==device int64 hash) and vtest.py (V(V0)≈0, monotonic). Then the beam — default to the V-ONLY driver:

cd /mnt/data/v6e && nohup ~/tpu-env/bin/python gcp_beam_v_only.py \
  --b-global <B> --num-steps 100 --start-pid <a> --end-pid <b> --parent-chunk 131072 \
  --tree-dir /dev/shm/trees --out /mnt/data/out/run.json > /mnt/data/out/run.log 2>&1 &

• USE gcp_beam_v_only.py (V-only), NOT gcp_beam_v6e.py (V+qshort), for the AZ v4 V. qshort (m23_v3 Q) MISRANKS children and INFLATES paths: confirmed 2026-06-12 pid 992 = 96 (qshort 96M) vs 78 (V-only 48M) — V-only at half the width + no sym beat the merged floor (85) by 7, qshort was +18 worse. This is Rule 15 (qshort regresses on AZ v4 V) in the TPU kernel. gcp_beam_v_only.py is NOT in the GCS bucket by default — scp it from megaminx/kaggle_notebooks/tpu_beam_spmd_jax/. Its kernel jax_beam_spmd_v_only.py IS staged (8-rank-safe packing). No --k-sym/--no-meta flags (single-view, no meta; uses parent_chunk streaming).
• V-only single-view plateaus on width (pid 992: 48M=64M=78); to push lower needs sym diversity or higher --alpha. Per-step 110s at 48M streaming (2.4 h/pid), ~170s at 64M.
• The qshort+sym driver gcp_beam_v6e.py --k-sym 4 ... --no-meta is retained ONLY if a future re-distilled Q is shown to help; until then it's a path-inflating trap. Wall is super-linear in B_local (~`B_local^1.8`); 8-chip 96M needs meta (no-meta ceiling ≈64M) at ~222 s/step.

6. Teardown

gcloud compute instances delete <name> --zone=<ZONE> --quiet stops the meter (flex VMs can't be "stopped", only deleted). Detach/keep the hyperdisk with auto-delete=no (or delete it for $0 — GCS is the source of truth). Verify gcloud compute instances list shows nothing of ours running.