Add local to csr_eq_segment

Author: Mikolaj Komar

include/dr/mp/algorithms/reduce.hpp

@@ -35,10 +35,11 @@ inline auto dpl_reduce(rng::forward_range auto &&r, auto &&binary_op) {
                          sycl::known_identity_v<Fn, T>, binary_op);
     } else {
       dr::drlog.debug("  peel 1st value\n");
+      auto base = *rng::begin(r);
       return std::reduce(dpl_policy(),
                          dr::__detail::direct_iterator(rng::begin(r) + 1),
                          dr::__detail::direct_iterator(rng::end(r)),
-                         sycl_get(*rng::begin(r)), binary_op);
+                         sycl_get(base), binary_op);
     }
   }
 #else

include/dr/mp/containers/matrix_formats/csr_eq_segment.hpp

@@ -235,6 +235,36 @@ template <typename DSM> class csr_eq_segment_iterator {
     return dr::__detail::drop_segments(dsm_->segments(), segment_index_,
                                        index_);
   }
+  
+  auto local() const {
+    const auto my_process_segment_index = dsm_->rows_backend_.getrank();
+
+    assert(my_process_segment_index == segment_index_);
+    // auto offset = dsm_->row_offsets_[segment_index_];
+    // auto row_size = dsm_->row_size_;
+    auto segment_size = dsm_->vals_data_->segment_size();
+    auto local_vals = dsm_->vals_data_->segments()[segment_index_].begin().local();
+    auto local_vals_range = rng::subrange(local_vals, local_vals + segment_size);
+    auto local_cols = dsm_->cols_data_->segments()[segment_index_].begin().local();
+    auto local_cols_range = rng::subrange(local_cols, local_cols + segment_size);
+    // auto local_rows = dsm_->rows_data_;
+    auto zipped_results = rng::views::zip(local_vals_range, local_cols_range);
+    auto enumerated_zipped = rng::views::enumerate(zipped_results);
+    auto transformer = [&](auto entry) {
+      auto [index, pair] = entry;
+      auto [val, column] = pair;
+      auto row = 0; //TODO fix calculating row - it results in segfault
+      // auto row = rng::distance(
+      //           local_rows,
+      //           std::upper_bound(local_rows, local_rows + row_size, offset + index) -
+      //               1);
+      dr::index<index_type> index_obj(row, column);
+      value_type entry_obj(index_obj, val);
+      return entry_obj;
+    };
+    auto transformed_res = rng::transform_view(enumerated_zipped, transformer);
+    return transformed_res.begin();
+  }
 
 private:
   // all fields need to be initialized by default ctor so every default