Function compute_multi_indices

fem/tensorcoefficient.cpp:210–273

index format: 'ij,jk->ik' (result after '->' is mandatory!); return: input data, result data, full set

        // index format: 'ij,jk->ik' (result after '->' is mandatory!); return: input data, result data,
        // full set
        Array<MultiIndex> compute_multi_indices(const string &index_signature,
                                                const Array<shared_ptr<CoefficientFunction>> &cfs) {
            Array<MultiIndex> idx_sets(cfs.Size() + 2);
            MultiIndex *current_idx_set = idx_sets.begin();
            MultiIndex &full_idx_set = idx_sets[cfs.Size() + 1];

            Array<char> chars;
            Array<int> char_counts;
            Array<char> free_symbols;

            int subset_cnt = 0;
            int subset_idx = 0;
            bool result_section = false;

            for_each(begin(index_signature), end(index_signature), [&](const char idx) {
                if (idx == '>' || idx == '\0')
                    return;

                if (idx == '-')
                    result_section = true;

                if (idx == ',' || idx == '-') {
                    ++current_idx_set;
                    ++subset_cnt;
                    subset_idx = 0;
                    return;
                }

                if ((idx < 'a' || idx > 'z') && (idx < 'A' || idx > 'Z'))
                    throw NG_EXCEPTION("invalid index character detected -- use only a-z, A-Z");

                if (!chars.Contains(idx)) {
                    if (result_section)
                        throw NG_EXCEPTION("detected 'result indices' not present in the inputs");

                    size_t subset_dim_i = 1;
                    if (cfs[subset_cnt]->Dimensions().Size() <= 1)
                        if (subset_idx > 1)
                            throw NG_EXCEPTION("tensor order mismatch");
                        else
                            subset_dim_i = cfs[subset_cnt]->Dimension();
                    else if (subset_idx + 1 > cfs[subset_cnt]->Dimensions().Size())
                        throw NG_EXCEPTION("tensor order mismatch");
                    else
                        subset_dim_i = cfs[subset_cnt]->Dimensions()[subset_idx];

                    full_idx_set.Append(Index{idx, chars.Size(), subset_dim_i});
                    current_idx_set->Append(full_idx_set[chars.Size()]);
                    chars.Append(idx);
                    char_counts.Append(1);
                } else if (!result_section && cfs[subset_cnt]->Dimensions()[subset_idx] !=
                                              full_idx_set[chars.Pos(idx)].dim) {
                    throw NG_EXCEPTION("dimensions of contracted indices do not match");
                } else {
                    current_idx_set->Append(full_idx_set[chars.Pos(idx)]);
                    if (!result_section)
                        char_counts[chars.Pos(idx)] += 1;
                }