[mxfp] handle values close to max correctly w/o overflow #8356
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lezcano
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yangshuxin
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…#8356) Need to clamp since due to rounding, we can have overflow that was within the range before quantization. e.g., 3.3895e+38 -> log2(3.3895e+38 / max_fp8e4m3=448) ~= 119.17 -> round up to 120 + exp_bias=127 -> scale=247 3.3895e+38 / 2**120 ~= 254.9976 -> round to 256 in fp8e4m3fn Dequantization: 256 * 2**120 > 3.4e38 overflowing 3.38953139e38 <!--- The core Triton is a small number of people, and we receive many PRs (thank you!). To help us review your code more quickly, **if you are a new contributor (less than 3 PRs merged) we ask that you complete the following tasks and include the filled-out checklist in your PR description.** Complete the following tasks before sending your PR, and replace `[ ]` with `[x]` to indicate you have done them. --> # New contributor declaration - [x] I am not making a trivial change, such as fixing a typo in a comment. - [x] I have written a PR description following these [rules](https://cbea.ms/git-commit/#why-not-how). - [x] I have run `pre-commit run --from-ref origin/main --to-ref HEAD`. - Select one of the following. - [x] I have added tests. - `/test` for `lit` tests - `/unittest` for C++ tests - `/python/test` for end-to-end tests - [ ] This PR does not need a test because `FILL THIS IN`. - Select one of the following. - [x] I have not added any `lit` tests. - [ ] The `lit` tests I have added follow these [best practices](https://mlir.llvm.org/getting_started/TestingGuide/#filecheck-best-practices), including the "tests should be minimal" section. (Usually running Python code and using the instructions it generates is not minimal.)
Jokeren
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Need to clamp since due to rounding, we can have overflow that was within the range before quantization. e.g., 3.3895e+38 -> log2(3.3895e+38 / max_fp8e4m3=448) ~= 119.17 -> round up to 120 + exp_bias=127 -> scale=247 3.3895e+38 / 2**120 ~= 254.9976 -> round to 256 in fp8e4m3fn Dequantization: 256 * 2**120 > 3.4e38 overflowing 3.38953139e38 <!--- The core Triton is a small number of people, and we receive many PRs (thank you!). To help us review your code more quickly, **if you are a new contributor (less than 3 PRs merged) we ask that you complete the following tasks and include the filled-out checklist in your PR description.** Complete the following tasks before sending your PR, and replace `[ ]` with `[x]` to indicate you have done them. --> # New contributor declaration - [x] I am not making a trivial change, such as fixing a typo in a comment. - [x] I have written a PR description following these [rules](https://cbea.ms/git-commit/#why-not-how). - [x] I have run `pre-commit run --from-ref origin/main --to-ref HEAD`. - Select one of the following. - [x] I have added tests. - `/test` for `lit` tests - `/unittest` for C++ tests - `/python/test` for end-to-end tests - [ ] This PR does not need a test because `FILL THIS IN`. - Select one of the following. - [x] I have not added any `lit` tests. - [ ] The `lit` tests I have added follow these [best practices](https://mlir.llvm.org/getting_started/TestingGuide/#filecheck-best-practices), including the "tests should be minimal" section. (Usually running Python code and using the instructions it generates is not minimal.)
ita9naiwa
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Oct 12, 2025
…#8356) Need to clamp since due to rounding, we can have overflow that was within the range before quantization. e.g., 3.3895e+38 -> log2(3.3895e+38 / max_fp8e4m3=448) ~= 119.17 -> round up to 120 + exp_bias=127 -> scale=247 3.3895e+38 / 2**120 ~= 254.9976 -> round to 256 in fp8e4m3fn Dequantization: 256 * 2**120 > 3.4e38 overflowing 3.38953139e38 <!--- The core Triton is a small number of people, and we receive many PRs (thank you!). To help us review your code more quickly, **if you are a new contributor (less than 3 PRs merged) we ask that you complete the following tasks and include the filled-out checklist in your PR description.** Complete the following tasks before sending your PR, and replace `[ ]` with `[x]` to indicate you have done them. --> # New contributor declaration - [x] I am not making a trivial change, such as fixing a typo in a comment. - [x] I have written a PR description following these [rules](https://cbea.ms/git-commit/#why-not-how). - [x] I have run `pre-commit run --from-ref origin/main --to-ref HEAD`. - Select one of the following. - [x] I have added tests. - `/test` for `lit` tests - `/unittest` for C++ tests - `/python/test` for end-to-end tests - [ ] This PR does not need a test because `FILL THIS IN`. - Select one of the following. - [x] I have not added any `lit` tests. - [ ] The `lit` tests I have added follow these [best practices](https://mlir.llvm.org/getting_started/TestingGuide/#filecheck-best-practices), including the "tests should be minimal" section. (Usually running Python code and using the instructions it generates is not minimal.)
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Need to clamp since due to rounding, we can have overflow that was within
the range before quantization.
e.g., 3.3895e+38 -> log2(3.3895e+38 / max_fp8e4m3=448) ~= 119.17 -> round
up to 120 + exp_bias=127 -> scale=247
3.3895e+38 / 2120 ~= 254.9976 -> round to 256 in fp8e4m3fn
Dequantization: 256 * 2120 > 3.4e38 overflowing 3.38953139e38
New contributor declaration
I am not making a trivial change, such as fixing a typo in a comment.
I have written a PR description following these
rules.
I have run
pre-commit run --from-ref origin/main --to-ref HEAD.Select one of the following.
/testforlittests/unittestfor C++ tests/python/testfor end-to-end testsFILL THIS IN.Select one of the following.
littests.littests I have added follow these best practices,including the "tests should be minimal" section. (Usually running Python code
and using the instructions it generates is not minimal.)