[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
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wconstab
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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
ezyang
reviewed
Aug 13, 2025
ezyang
reviewed
Aug 13, 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-poisoned]
wconstab
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Aug 13, 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: a13ee46 Pull Request resolved: #160283
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]
wconstab
added a commit
that referenced
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Aug 13, 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: 55f1f0b Pull Request resolved: #160283
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chuanhaozhuge
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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 ``` Pull Request resolved: #160283 Approved by: https://github.com/ezyang
chuanhaozhuge
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Aug 18, 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 ``` Pull Request resolved: #160283 Approved by: https://github.com/ezyang
can-gaa-hou
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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 ``` Pull Request resolved: pytorch#160283 Approved by: https://github.com/ezyang
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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 ``` Pull Request resolved: pytorch#160283 Approved by: https://github.com/ezyang
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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):
cc @H-Huang @awgu @wanchaol @fegin @fduwjj @wz337 @d4l3k @pragupta