intrinsics module with alternative implementations #915
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jalvesz
changed the title
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One philosophical question: should the fsum interface be renamed to Regarding the kahan versions, given that the accuracy gains are close between the pure chunked version and the kahan one, I'm wondering which level of support should be enabled to switch between them? |
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IMHO shorter names are better, and don't see a problem if they overlap with the intrinsics. First, because one can always pick the right version: use stdlib_intrinsics, only: dot_productvs. ! Force using intrinsic
intrinsic :: dot_productAnd then because they can be augmented by more/different arguments c = dot_product(a,b) ! intrinsic
c = dot_product(a,b,mode='kahan') ! stdlib
c = dot_product(a,b,mode='blocked') ! stdlib
...I find this more elegant and definitely not confusing. |
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| #### Description | ||
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| The `stdlib_sum` function can replace the intrinsic `sum` for `real` or `complex` arrays. It follows a chunked implementation which maximizes vectorization potential as well as reducing the round-off error. This procedure is recommended when summing large arrays, for repetitive summation of smaller arrays consider the classical `sum`. |
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No specific reason, when implementing the first version my first need was for reals and so that's what I proposed here. I can test if it also brings benefits for integers and extend the template.
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| #### Description | ||
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| The `stdlib_dot_product_kahan` function can replace the intrinsic `dot_product` for 1D `real` or `complex` arrays. It follows a chunked implementation which maximizes vectorization potential , complemented by the same `elemental` kernel based on the [kahan summation](https://en.wikipedia.org/wiki/Kahan_summation_algorithm) used for `stdlib_sum` to reduce the round-off error. |
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is the license of wikipedia in agreement with the MIT license of stdlib?
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I did not take content directly from Wikipedia, I just cited the wiki page that summarizes the kahan summation algorithm. Would such citation be problematic?
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Ok. Most content of WIkipedia is under CC BY-SA4.0, which states: "Share Alike—If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original."
To avoid any potential confusions/issues, maybe could you reference to the original paper: https://doi.org/10.1145%2F363707.363723 ?
| !! This interface provides standard conforming call for sum of elements of any rank. | ||
| !! The 1-D base implementation follows a chunked approach for optimizing performance and increasing accuracy. | ||
| !! The `N-D` interfaces calls upon the `(N-1)-D` implementation. | ||
| !! Supported data types include `real` and `complex`. |
I prefer to keep use stdlib_intrinsics, only: dot_product => stdlib_dot_productWith this approach, the user will not inadvertently use the stdlib implementation.
This approach would break backward compatibility with the intrinsics. IMO I prefer the previous approach (either an overlap, or a name with a prefix |
Co-authored-by: Jeremie Vandenplas <[email protected]>
Co-authored-by: Jeremie Vandenplas <[email protected]>
Co-authored-by: Jeremie Vandenplas <[email protected]>
Add intrinsics module containing replacements for intrinsic function where some feature is found interesting: faster implementation, better accuracy, both simultaneously.
This PR follows the discussion in discourse https://fortran-lang.discourse.group/t/lfortran-now-supports-all-intrinsic-functions/8844/41 and it's based on https://github.com/jalvesz/fast_math
stdlib_sumandstdlib_sum_kahan)stdlib_dot_productandstdlib_dot_product_kahan)cc: @fortran-lang/stdlib @perazz @certik @jvdp1