Improve performance of surveying => faster search

- def.h: changed vectors for inorganics to contain uint8_t instead of bool which improves the performance when using std::fill and std::memset to batch-set the whole array
- survey.cpp: using std::memset instead of direct assignment to reset the inorganic vectors, also using the actual size of each vector for the call
- changelog.txt: add note concerning the changes

docs/changelog.txt

@@ -42,6 +42,7 @@ changelog.txt uses a syntax similar to RST, with a few special sequences:
 
 ## Misc Improvements
 - `tweak` hide-priority: changed so that priorities stay hidden (or visible) when exiting and re-entering the designations menu
+- `embark-assistant`: slightly improved performance of surveying and improved code a little
 
 ## Lua
 - ``gui.Painter``: fixed error when calling ``viewport()`` method

plugins/embark-assistant/defs.h

@@ -91,9 +91,12 @@ namespace embark_assist {
             int16_t river_elevation = 100;
             int8_t adamantine_level;  // -1 = none, 0 .. 3 = cavern 1 .. magma sea. Currently not used beyond present/absent.
             int8_t magma_level;  // -1 = none, 0 .. 3 = cavern 3 .. surface/volcano
-            std::vector<bool> metals;
+            // using uint8_t instead of bool as vector<bool> gets optimized for a small memory footprint which leads to a significant overhead when iterating over all entries, 
-            std::vector<bool> economics;
+            // also there seems to be no template specialization for std::fill in MSVS C++11 in regards to std::vector<bool> and std::memset does not work as expected (=> not at all that is)
-            std::vector<bool> minerals;
+            // have a look here https://github.com/DFHack/dfhack/pull/1771#discussion_r579498636 for the related discussion and furter resources
+            std::vector<uint8_t> metals;
+            std::vector<uint8_t> economics;
+            std::vector<uint8_t> minerals;
         };
 
         typedef std::array<std::array<mid_level_tile, 16>, 16> mid_level_tiles;

plugins/embark-assistant/survey.cpp

@@ -909,15 +909,14 @@ void inline copy_incursion_values(embark_assist::defs::mid_level_tile_incursion_
 //=================================================================================
 
 void reset_mlt_inorganics(embark_assist::defs::mid_level_tiles &mlts) {
-    const uint16_t size = mlts[0][0].metals.size();
     for (uint8_t i = 0; i < 16; i++) {
         for (uint8_t k = 0; k < 16; k++) {
             embark_assist::defs::mid_level_tile &mlt = mlts[i][k];
-            for (uint16_t l = 0; l < size; l++) {
+            // std::memset is much faster than std::fill and also faster than direct assignment - also std::fill might be compiled to std::memset but is not guaranteed to happen
-                mlt.metals[l] = false;
+            // have a look here for why: https://travisdowns.github.io/blog/2020/01/20/zero.html
-                mlt.economics[l] = false;
+            std::memset(&mlt.metals[0], false, mlt.metals.size() * sizeof(mlt.metals[0]));
-                mlt.minerals[l] = false;
+            std::memset(&mlt.economics[0], false, mlt.economics.size() * sizeof(mlt.economics[0]));
-            }
+            std::memset(&mlt.minerals[0], false, mlt.minerals.size() * sizeof(mlt.minerals[0]));
         }
     }
 }