refactor with a more simd-friendly api

[codecov[bot]]

Codecov Report

Patch coverage: 87.83% and project coverage change: -2.20 :warning:

Comparison is base (67fc199) 90.48% compared to head (4c33d2a) 88.29%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #24 +/- ## ========================================== - Coverage 90.48% 88.29% -2.20% ========================================== Files 41 41 Lines 26138 27687 +1549 ========================================== + Hits 23651 24445 +794 - Misses 2487 3242 +755 ``` | [Impacted Files](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah) | Coverage Δ | | |---|---|---| | [faer-core/src/lib.rs](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah#diff-ZmFlci1jb3JlL3NyYy9saWIucnM=) | `63.11% <ø> (-12.93%)` | :arrow_down: | | [faer-core/src/mul.rs](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah#diff-ZmFlci1jb3JlL3NyYy9tdWwucnM=) | `73.85% <ø> (-25.21%)` | :arrow_down: | | [faer-cholesky/src/lib.rs](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah#diff-ZmFlci1jaG9sZXNreS9zcmMvbGliLnJz) | `3.12% <12.50%> (+0.09%)` | :arrow_up: | | [faer-cholesky/src/llt/solve.rs](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah#diff-ZmFlci1jaG9sZXNreS9zcmMvbGx0L3NvbHZlLnJz) | `25.23% <27.58%> (+2.76%)` | :arrow_up: | | [faer-cholesky/src/ldlt\_diagonal/solve.rs](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah#diff-ZmFlci1jaG9sZXNreS9zcmMvbGRsdF9kaWFnb25hbC9zb2x2ZS5ycw==) | `44.73% <44.82%> (+9.78%)` | :arrow_up: | | [faer-cholesky/src/llt/reconstruct.rs](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah#diff-ZmFlci1jaG9sZXNreS9zcmMvbGx0L3JlY29uc3RydWN0LnJz) | `59.52% <53.33%> (-0.06%)` | :arrow_down: | | [faer-svd/src/bidiag.rs](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah#diff-ZmFlci1zdmQvc3JjL2JpZGlhZy5ycw==) | `82.41% <65.91%> (+4.34%)` | :arrow_up: | | [faer-qr/src/col\_pivoting/reconstruct.rs](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah#diff-ZmFlci1xci9zcmMvY29sX3Bpdm90aW5nL3JlY29uc3RydWN0LnJz) | `74.80% <71.87%> (-0.95%)` | :arrow_down: | | [faer-qr/src/no\_pivoting/reconstruct.rs](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah#diff-ZmFlci1xci9zcmMvbm9fcGl2b3RpbmcvcmVjb25zdHJ1Y3QucnM=) | `74.38% <73.52%> (-0.41%)` | :arrow_down: | | [faer-cholesky/src/llt/inverse.rs](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah#diff-ZmFlci1jaG9sZXNreS9zcmMvbGx0L2ludmVyc2UucnM=) | `75.40% <73.68%> (-1.16%)` | :arrow_down: | | ... and [30 more](https://codecov.io/gh/sarah-ek/faer-rs/pull/24?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah) | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sarah)

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