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Add specialized "permutation" transform (#1077)
* WIP: signed permutation * Simplify rotation matrix construction * Define integer quarter turn helper class * Add signed permutation class * Rename pos/neg to remove ambiguity * Use explicit characters and add determinant error checking * Add documentation
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| Original file line number | Diff line number | Diff line change |
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| //----------------------------------*-C++-*----------------------------------// | ||
| // Copyright 2024 UT-Battelle, LLC, and other Celeritas developers. | ||
| // See the top-level COPYRIGHT file for details. | ||
| // SPDX-License-Identifier: (Apache-2.0 OR MIT) | ||
| //---------------------------------------------------------------------------// | ||
| //! \file orange/transform/SignedPermutation.cc | ||
| //---------------------------------------------------------------------------// | ||
| #include "SignedPermutation.hh" | ||
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| #include "orange/MatrixUtils.hh" | ||
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| namespace celeritas | ||
| { | ||
| //---------------------------------------------------------------------------// | ||
| /*! | ||
| * Construct with an identity permutation. | ||
| */ | ||
| SignedPermutation::SignedPermutation() | ||
| : SignedPermutation{ | ||
| SignedAxes{{{'+', Axis::x}, {'+', Axis::y}, {'+', Axis::z}}}} | ||
| { | ||
| } | ||
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| //---------------------------------------------------------------------------// | ||
| /*! | ||
| * Construct with a permutation vector. | ||
| */ | ||
| SignedPermutation::SignedPermutation(SignedAxes permutation) : compressed_{0} | ||
| { | ||
| EnumArray<Axis, bool> encountered_ax{false, false, false}; | ||
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| SquareMatrix<int, 3> explicit_mat; | ||
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| for (auto ax : {Axis::z, Axis::y, Axis::x}) | ||
| { | ||
| auto new_ax_sign = permutation[ax]; | ||
| CELER_VALIDATE(new_ax_sign.first == '+' || new_ax_sign.first == '-', | ||
| << "invalid permutation sign '" << new_ax_sign.first | ||
| << "'"); | ||
| CELER_VALIDATE(new_ax_sign.second < Axis::size_, | ||
| << "invalid permutation axis"); | ||
| CELER_VALIDATE(!encountered_ax[new_ax_sign.second], | ||
| << "duplicate axis " << to_char(new_ax_sign.second) | ||
| << " in permutation matrix input"); | ||
| encountered_ax[new_ax_sign.second] = true; | ||
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| // Push back "flip bit" | ||
| compressed_ <<= 1; | ||
| compressed_ |= (new_ax_sign.first == '-' ? 0b1 : 0b0); | ||
| // Push back "new axis" | ||
| compressed_ <<= 2; | ||
| compressed_ |= to_int(new_ax_sign.second); | ||
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| // Explicitly construct row in error checking matrix | ||
| for (auto oax : {Axis::x, Axis::y, Axis::z}) | ||
| { | ||
| explicit_mat[to_int(ax)][to_int(oax)] = [oax, new_ax_sign] { | ||
| if (oax != new_ax_sign.second) | ||
| return 0; | ||
| if (new_ax_sign.first == '-') | ||
| return -1; | ||
| return 1; | ||
| }(); | ||
| } | ||
| } | ||
| int det = determinant(explicit_mat); | ||
| CELER_VALIDATE( | ||
| det == +1, | ||
| << "invalid rotation matrix: determinant should be +1 but is " << det); | ||
| } | ||
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| //---------------------------------------------------------------------------// | ||
| /*! | ||
| * Reconstruct the permutation. | ||
| */ | ||
| auto SignedPermutation::permutation() const -> SignedAxes | ||
| { | ||
| SignedAxes result; | ||
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| UIntT temp = compressed_; | ||
| for (auto ax : range(Axis::size_)) | ||
| { | ||
| // Copy "new axis" | ||
| result[ax].second = to_axis(temp & 0b11); | ||
| temp >>= 2; | ||
| // Push back "flip bit" | ||
| result[ax].first = temp & 0b1 ? '-' : '+'; | ||
| temp >>= 1; | ||
| } | ||
| return result; | ||
| } | ||
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| //---------------------------------------------------------------------------// | ||
| /*! | ||
| * Get a view to the data for type-deleted storage. | ||
| */ | ||
| auto SignedPermutation::data() const -> DataArray | ||
| { | ||
| static_assert( | ||
| max_value() == static_cast<UIntT>(static_cast<real_type>(max_value())), | ||
| "cannot round-trip real type and short int"); | ||
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| return {static_cast<real_type>(compressed_)}; | ||
| } | ||
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| //---------------------------------------------------------------------------// | ||
| /*! | ||
| * Make a permutation by rotating about the given axis. | ||
| */ | ||
| SignedPermutation make_permutation(Axis ax, QuarterTurn theta) | ||
| { | ||
| CELER_EXPECT(ax < Axis::size_); | ||
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| auto to_sign = [](int v) { return v < 0 ? '-' : '+'; }; | ||
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| int const cost = cos(theta); | ||
| int const sint = sin(theta); | ||
| Axis const uax = to_axis((to_int(ax) + 1) % 3); | ||
| Axis const vax = to_axis((to_int(ax) + 2) % 3); | ||
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| SignedPermutation::SignedAxes r; | ||
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| // Axis of rotation is unchanged | ||
| r[ax] = {to_sign(1), ax}; | ||
| if (cost != 0) | ||
| { | ||
| r[uax] = {to_sign(cost), uax}; | ||
| r[vax] = {to_sign(cost), vax}; | ||
| } | ||
| else | ||
| { | ||
| r[uax] = {to_sign(-sint), vax}; | ||
| r[vax] = {to_sign(sint), uax}; | ||
| } | ||
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| return SignedPermutation{r}; | ||
| } | ||
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| //---------------------------------------------------------------------------// | ||
| } // namespace celeritas |
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