Provides compile-time contraction pattern analysis to determine optimal operation to perform.
A C++ compiler with C++17 support.
The following libraries are required to build EinsumsInCpp:
- BLAS and LAPACK.
- A Fast Fourier Transform library, either FFTW3 or DFT from MKL.
On my personal development machine, I use MKL for the above requirements. On GitHub Actions, stock BLAS, LAPACK, and FFTW3 are used.
Optional requirements:
- For call stack backtracing, refer to the requirements listed here.
This will optimize at compile-time to a BLAS dgemm call.
#include "einsums/TensorAlgebra.hpp"
using einsums; // Provides Tensor and create_random_tensor
using einsums::TensorAlgebra; // Provides einsum and Indices
using einsums::TensorAlgrebra::Index; // Provides i, j, k
Tensor<2> A = create_random_tensor("A", 7, 7);
Tensor<2> B = create_random_tensor("B", 7, 7);
Tensor<2> C{"C", 7, 7};
einsum(Indices{i, j}, &C, Indices{i, k}, A, Indices{k, j}, B);Two-Electron Contribution to the Fock Matrix
#include "einsums/TensorAlgebra.hpp"
using namespace einsums;
void build_Fock_2e_einsum(Tensor<2> *F,
const Tensor<4> &g,
const Tensor<2> &D) {
using namespace einsums::TensorAlgebra;
using namespace einsums::TensorAlgebra::Index;
// Will compile-time optimize to BLAS gemv
einsum(1.0, Indices{p, q}, F,
2.0, Indices{p, q, r, s}, g, Indices{r, s}, D);
// As written cannot be optimized.
// A generic arbitrary contraction function will be used.
einsum(1.0, Indices{p, q}, F,
-1.0, Indices{p, r, q, s}, g, Indices{r, s}, D);
}
W Intermediates in CCD
Wmnij = g_oooo;
// Compile-time optimizes to gemm
einsum(1.0, Indices{m, n, i, j}, &Wmnij,
0.25, Indices{i, j, e, f}, t_oovv,
Indices{m, n, e, f}, g_oovv);
Wabef = g_vvvv;
// Compile-time optimizes to gemm
einsum(1.0, Indices{a, b, e, f}, &Wabef,
0.25, Indices{m, n, e, f}, g_oovv,
Indices{m, n, a, b}, t_oovv);
Wmbej = g_ovvo;
// As written uses generic arbitrary contraction function
einsum(1.0, Indices{m, b, e, j}, &Wmbej,
-0.5, Indices{j, n, f, b}, t_oovv,
Indices{m, n, e, f}, g_oovv);CCD Energy
/// Compile-time optimizes to a dot product
einsum(0.0, Indices{}, &e_ccd,
0.25, Indices{i, j, a, b}, new_t_oovv,
Indices{i, j, a, b}, g_oovv);