[C10D] Add check_rng_sync util #160283
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[C10D] Add check_rng_sync util #160283
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Debugs RNG desync by checking the current state on each rank in the group and summarizing the differences if any are detected. Notes: - used allgather instead of gather since its simpler to do this SPMD rather than add conditional behavior, though I could be convinced we only want to log on rank0. Usage: `check_rng_sync(generator, group)` Prints something like this: (cuda): ``` [rank0]:E0808 ] Generator desync detected: [rank0]:E0808 ] Ranks (Seed, Offset) values [rank0]:E0808 ] ------- ----------------------- [rank0]:E0808 ] 0 (456, 0) [rank0]:E0808 ] 1 (123, 4) [rank0]:E0808 ] 2-3 (123, 0) ``` (cpu): ``` [rank2]:E0810 ] Generator desync detected: [rank2]:E0810 ] Ranks Generator State Hash values [rank2]:E0810 ] ------- ----------------------------- [rank2]:E0810 ] 0 7633364531954955665 [rank2]:E0810 ] 1 8807615394212033278 [rank2]:E0810 ] 2-3 -6150027303226666531 ``` [ghstack-poisoned]
🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/160283
Note: Links to docs will display an error until the docs builds have been completed. ⏳ No Failures, 4 PendingAs of commit 2e1102a with merge base 556e2a7 ( This comment was automatically generated by Dr. CI and updates every 15 minutes. |
wconstab
added a commit
that referenced
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Aug 10, 2025
Debugs RNG desync by checking the current state on each rank in the group and summarizing the differences if any are detected. Notes: - used allgather instead of gather since its simpler to do this SPMD rather than add conditional behavior, though I could be convinced we only want to log on rank0. Usage: `check_rng_sync(generator, group)` Prints something like this: (cuda): ``` [rank0]:E0808 ] Generator desync detected: [rank0]:E0808 ] Ranks (Seed, Offset) values [rank0]:E0808 ] ------- ----------------------- [rank0]:E0808 ] 0 (456, 0) [rank0]:E0808 ] 1 (123, 4) [rank0]:E0808 ] 2-3 (123, 0) ``` (cpu): ``` [rank2]:E0810 ] Generator desync detected: [rank2]:E0810 ] Ranks Generator State Hash values [rank2]:E0810 ] ------- ----------------------------- [rank2]:E0810 ] 0 7633364531954955665 [rank2]:E0810 ] 1 8807615394212033278 [rank2]:E0810 ] 2-3 -6150027303226666531 ``` ghstack-source-id: 3d60739 Pull Request resolved: #160283
This was referenced Aug 10, 2025
Debugs RNG desync by checking the current state on each rank in the group and summarizing the differences if any are detected. Notes: - used allgather instead of gather since its simpler to do this SPMD rather than add conditional behavior, though I could be convinced we only want to log on rank0. Usage: `check_rng_sync(generator, group)` Prints something like this: (cuda): ``` [rank0]:E0808 ] Generator desync detected: [rank0]:E0808 ] Ranks (Seed, Offset) values [rank0]:E0808 ] ------- ----------------------- [rank0]:E0808 ] 0 (456, 0) [rank0]:E0808 ] 1 (123, 4) [rank0]:E0808 ] 2-3 (123, 0) ``` (cpu): ``` [rank2]:E0810 ] Generator desync detected: [rank2]:E0810 ] Ranks Generator State Hash values [rank2]:E0810 ] ------- ----------------------------- [rank2]:E0810 ] 0 7633364531954955665 [rank2]:E0810 ] 1 8807615394212033278 [rank2]:E0810 ] 2-3 -6150027303226666531 ``` cc H-Huang awgu wanchaol fegin fduwjj wz337 d4l3k pragupta [ghstack-poisoned]
Debugs RNG desync by checking the current state on each rank in the group and summarizing the differences if any are detected. Notes: - used allgather instead of gather since its simpler to do this SPMD rather than add conditional behavior, though I could be convinced we only want to log on rank0. Usage: `check_rng_sync(generator, group)` Prints something like this: (cuda): ``` [rank0]:E0808 ] Generator desync detected: [rank0]:E0808 ] Ranks (Seed, Offset) values [rank0]:E0808 ] ------- ----------------------- [rank0]:E0808 ] 0 (456, 0) [rank0]:E0808 ] 1 (123, 4) [rank0]:E0808 ] 2-3 (123, 0) ``` (cpu): ``` [rank2]:E0810 ] Generator desync detected: [rank2]:E0810 ] Ranks Generator State Hash values [rank2]:E0810 ] ------- ----------------------------- [rank2]:E0810 ] 0 7633364531954955665 [rank2]:E0810 ] 1 8807615394212033278 [rank2]:E0810 ] 2-3 -6150027303226666531 ``` cc H-Huang awgu wanchaol fegin fduwjj wz337 d4l3k pragupta [ghstack-poisoned]
Debugs RNG desync by checking the current state on each rank in the group and summarizing the differences if any are detected. Notes: - used allgather instead of gather since its simpler to do this SPMD rather than add conditional behavior, though I could be convinced we only want to log on rank0. Usage: `check_rng_sync(generator, group)` Prints something like this: (cuda): ``` [rank0]:E0808 ] Generator desync detected: [rank0]:E0808 ] Ranks (Seed, Offset) values [rank0]:E0808 ] ------- ----------------------- [rank0]:E0808 ] 0 (456, 0) [rank0]:E0808 ] 1 (123, 4) [rank0]:E0808 ] 2-3 (123, 0) ``` (cpu): ``` [rank2]:E0810 ] Generator desync detected: [rank2]:E0810 ] Ranks Generator State Hash values [rank2]:E0810 ] ------- ----------------------------- [rank2]:E0810 ] 0 7633364531954955665 [rank2]:E0810 ] 1 8807615394212033278 [rank2]:E0810 ] 2-3 -6150027303226666531 ``` [ghstack-poisoned]
Debugs RNG desync by checking the current state on each rank in the group and summarizing the differences if any are detected. Notes: - used allgather instead of gather since its simpler to do this SPMD rather than add conditional behavior, though I could be convinced we only want to log on rank0. Usage: `check_rng_sync(generator, group)` Prints something like this: (cuda): ``` [rank0]:E0808 ] Generator desync detected: [rank0]:E0808 ] Ranks (Seed, Offset) values [rank0]:E0808 ] ------- ----------------------- [rank0]:E0808 ] 0 (456, 0) [rank0]:E0808 ] 1 (123, 4) [rank0]:E0808 ] 2-3 (123, 0) ``` (cpu): ``` [rank2]:E0810 ] Generator desync detected: [rank2]:E0810 ] Ranks Generator State Hash values [rank2]:E0810 ] ------- ----------------------------- [rank2]:E0810 ] 0 7633364531954955665 [rank2]:E0810 ] 1 8807615394212033278 [rank2]:E0810 ] 2-3 -6150027303226666531 ``` [ghstack-poisoned]
ezyang
reviewed
Aug 13, 2025
| # [rank0]:E0808 ] ------- ----------------------- | ||
| # [rank0]:E0808 ] 0 (456, 0) | ||
| # [rank0]:E0808 ] 1 (123, 4) | ||
| # [rank0]:E0808 ] 2-3 (123, 0) |
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Can you not have the function also return a str
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Yea, I can do that.
| all_states = [torch.empty_like(local_state) for _ in range(group.size())] | ||
| torch.distributed.all_gather(all_states, local_state) | ||
| seeds_offsets = [ | ||
| (state[:8].view(torch.uint64).item(), state[8:].view(torch.uint64).item()) |
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Remind me what's going on here?
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It's seed,offset both uint64_t packed together into a 16-byte, iirc
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Stack from ghstack (oldest at bottom):
Debugs RNG desync by checking the current state on each rank in the group and summarizing the differences if any are detected.
Notes:
Usage:
check_rng_sync(generator, group)Prints something like this:
(cuda):
(cpu):