Quaternion.cxx

// Copyright 2023, UChicago Argonne, LLC
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// Software Name: NEML2 -- the New Engineering material Model Library, version 2
// By: Argonne National Laboratory
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#include "neml2/tensors/Quaternion.h"
 
#include "neml2/tensors/R2.h"
#include "neml2/tensors/Scalar.h"
 
namespace neml2
{
 
Quaternion
Quaternion::fill(const Real & s,
                 const Real & q1,
                 const Real & q2,
                 const Real & q3,
                 const torch::TensorOptions & options)
{
  return Quaternion::fill(
      Scalar(s, options), Scalar(q1, options), Scalar(q2, options), Scalar(q3, options));
}
 
Quaternion
Quaternion::fill(const Scalar & s, const Scalar & q1, const Scalar & q2, const Scalar & q3)
{
  return Quaternion(torch::stack({s, q1, q2, q3}, -1), s.batch_dim());
}
 
Scalar
Quaternion::operator()(TorchSize i) const
{
  return FixedDimTensor<Quaternion, 4>::base_index({i});
}
 
R2
Quaternion::to_R2() const
{
  const Quaternion & q = *this;
 
  Scalar v1s = q(1) * q(1);
  Scalar v2s = q(2) * q(2);
  Scalar v3s = q(3) * q(3);
 
  return R2::fill(1 - 2 * v2s - 2 * v3s,
                  2 * (q(1) * q(2) - q(3) * q(0)),
                  2 * (q(1) * q(3) + q(2) * q(0)),
                  2 * (q(1) * q(2) + q(3) * q(0)),
                  1 - 2 * v1s - 2 * v3s,
                  2 * (q(2) * q(3) - q(1) * q(0)),
                  2 * (q(1) * q(3) - q(2) * q(0)),
                  2 * (q(2) * q(3) + q(1) * q(0)),
                  1 - 2 * v1s - 2 * v2s);
}
} // namespace neml2