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Minor doc updates. #16211

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Nov 2, 2023
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Minor doc updates. #16211

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41 changes: 30 additions & 11 deletions include/deal.II/base/symmetric_tensor.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1800,6 +1800,9 @@ SymmetricTensor<rank_, dim, Number>::memory_consumption()

namespace internal
{
/**
* Perform the double contraction between two rank-2 symmetric tensors.
*/
template <int dim, typename Number, typename OtherNumber = Number>
DEAL_II_HOST DEAL_II_CONSTEXPR inline DEAL_II_ALWAYS_INLINE
typename SymmetricTensorAccessors::
Expand All @@ -1817,14 +1820,17 @@ namespace internal
{
case 1:
return data[0] * sdata[0];
default:
// Start with the non-diagonal part to avoid some multiplications by
// 2.

default:
// Start with the non-diagonal part. These values appear
// twice in the matrix, but are only stored once. So we can
// get the double-contraction sum for these elements using
// only one multiplication each, and at the end multiplying
// things by 2.
result_type sum = data[dim] * sdata[dim];
for (unsigned int d = dim + 1; d < (dim * (dim + 1) / 2); ++d)
sum += data[d] * sdata[d];
sum += sum; // sum = sum * 2.;
sum += sum; // sum *= 2

// Now add the contributions from the diagonal
for (unsigned int d = 0; d < dim; ++d)
Expand All @@ -1835,6 +1841,10 @@ namespace internal



/**
* Perform the double contraction between a rank-4 and a rank-2
* symmetric tensor.
*/
template <int dim, typename Number, typename OtherNumber = Number>
DEAL_II_HOST DEAL_II_CONSTEXPR inline DEAL_II_ALWAYS_INLINE
typename SymmetricTensorAccessors::
Expand All @@ -1861,6 +1871,10 @@ namespace internal



/**
* Perform the double contraction between a rank-2 and a rank-4
* symmetric tensor.
*/
template <int dim, typename Number, typename OtherNumber = Number>
DEAL_II_HOST DEAL_II_CONSTEXPR inline DEAL_II_ALWAYS_INLINE
typename SymmetricTensorAccessors::StorageType<
Expand All @@ -1883,11 +1897,15 @@ namespace internal
base_tensor_type tmp;
for (unsigned int i = 0; i < tmp.dimension; ++i)
{
// Start with the non-diagonal part
// Start with the non-diagonal part. These values appear
// twice in the matrix, but are only stored once. So we can
// get the double-contraction sum for these elements using
// only one multiplication each, and at the end multiplying
// things by 2.
value_type sum = data[dim] * sdata[dim][i];
for (unsigned int d = dim + 1; d < (dim * (dim + 1) / 2); ++d)
sum += data[d] * sdata[d][i];
sum += sum; // sum = sum * 2.;
sum += sum; // sum *= 2

// Now add the contributions from the diagonal
for (unsigned int d = 0; d < dim; ++d)
Expand All @@ -1899,6 +1917,9 @@ namespace internal



/**
* Perform the double contraction between two rank-4 symmetric tensors.
*/
template <int dim, typename Number, typename OtherNumber = Number>
DEAL_II_HOST DEAL_II_CONSTEXPR inline DEAL_II_ALWAYS_INLINE
typename SymmetricTensorAccessors::StorageType<
Expand Down Expand Up @@ -1927,7 +1948,7 @@ namespace internal
// Start with the non-diagonal part
for (unsigned int d = dim; d < (dim * (dim + 1) / 2); ++d)
tmp[i][j] += data[i][d] * sdata[d][j];
tmp[i][j] += tmp[i][j]; // tmp[i][j] = tmp[i][j] * 2;
tmp[i][j] += tmp[i][j]; // tmp[i][j] *= 2;

// Now add the contributions from the diagonal
for (unsigned int d = 0; d < dim; ++d)
Expand All @@ -1948,10 +1969,8 @@ DEAL_II_HOST DEAL_II_CONSTEXPR inline DEAL_II_ALWAYS_INLINE
SymmetricTensor<rank_, dim, Number>::operator*(
const SymmetricTensor<2, dim, OtherNumber> &s) const
{
// need to have two different function calls
// because a scalar and rank-2 tensor are not
// the same data type (see internal function
// above)
// Dispatch to functions that know the types of the involved
// arguments via overloads.
return internal::perform_double_contraction<dim, Number, OtherNumber>(data,
s.data);
}
Expand Down