Improve tiling speed (#195)

* Add a way to run tippecanoe single-threaded for profiling

* Do less work when the tilestats sample values list is already full

* Save a copy when retrieving the attribute key

* Fewer atomic operations

* Move string hashing from mbtiles to text

* Only do approximate attribute deduplication when writing tiles

* Feature dropping tests are sensitive to exact tile size

* All tile creators now create a string pool for the tile

* Features clipped away to nothing should not participate in that tile

* Revert "Only do approximate attribute deduplication when writing tiles"

This reverts commit c42b34b498.

* Also revert the related test changes

* Revert "Revert "Only do approximate attribute deduplication when writing tiles""

This reverts commit 18509876c3.

* Be more specific about the string hash function

* Use fnv1a instead of std::hash for everything

* Reduce the chance of hash collisions

* Stick a hash search on the front of the tree search in addpool

* Eliminate repeated hashing of the same string

* Switch instead of ifs in json parsing

* A few more cases to populate the hash in addpool

* Store the hash in the tree instead of recalculating

* Add explanatory comment for mysterious argument

* Fewer copies in attribute stringification

* Clean up ancient weirdness in JSON attribute stringification

* More serial_val cleanup

* Pass a serial_feature to rewrite instead of many broken-down arguments

* Get rid of the multiple geometries within `partial`

* Revert "Pass a serial_feature to rewrite instead of many broken-down arguments"

This reverts commit 6f4ab9b725.

* Goodbye, struct coalesce

* Revert "Features clipped away to nothing should not participate in that tile"

This reverts commit 124462fbdc.

* Migrating fields from partial to serial_feature

* Name reconciliation between serial_feature and partial

* Replace struct partial with an augmented serial_feature

* Fix some overzealous search-and-replace renaming

* Don't say struct so often

* Remove more of the former partial construction

* Commenting and cleaning up

* Trying again to avoid all these arguments to rewrite

* I swear I did this same thing before and it didn't work.

* More rewrite cleanup

* Exile --detect-shared-borders to its own file

* Add missing headers

* More commenting and cleanup

* More comments

* Sprinkle consts around

* Emplacing and std::moving

* More cleanup

* That shouldn't have worked after a std::move

* Don't need to allocate memory to compare keys

* Reduce use of the global string pool in tiling

* Another avoidable mvt_value construction

* Further reduction to explicit string pool passing

* These reverses are no longer optimizations

* These layernames can all be references

* Don't drag an unused layername string around with every feature

* Heed a compiler warning about potential buffer overflow

* Fix my confusion about which feature's string pool is relevant

* Avoid some unnecessary allocations in attribute accumulation

* Maybe faster serialization?

* Eliminate a comparison

* Do the same here

* Save a couple of allocations when parsing numbers in JSON

* Immediately assign features to layers instead of subdividing later

* Maintain tilestats for tippecanoe:retain_points_multiplier_sequence

* Crunch out more duplicate attribute values when writing out the tile

* Do tilestats for tippecanoe:retain_points_multiplier_first too

* Shell filters need to be real threads, even if nothing else does

* Simplify tippecanoe_minzoom/maxzoom representation

* Update version and changelog

tile-join.cpp

@@ -42,6 +42,7 @@
 #include "milo/dtoa_milo.h"
 #include "errors.hpp"
 #include "geometry.hpp"
+#include "thread.hpp"
 
 int pk = false;
 int pC = false;
@@ -85,6 +86,8 @@ void append_tile(std::string message, int z, unsigned x, unsigned y, std::map<st
 		exit(EXIT_MVT);
 	}
 
+	std::shared_ptr<std::string> tile_stringpool = std::make_shared<std::string>();
+
 	for (size_t l = 0; l < tile.layers.size(); l++) {
 		mvt_layer &layer = tile.layers[l];
 
@@ -213,7 +216,7 @@ void append_tile(std::string message, int z, unsigned x, unsigned y, std::map<st
 								outsv.s = joinval;
 
 								// Convert from double to int if the joined attribute is an integer
-								outval = stringified_to_mvt_value(outval.type, joinval.c_str());
+								outval = stringified_to_mvt_value(outval.type, joinval.c_str(), tile_stringpool);
 
 								attributes.insert(std::pair<std::string, std::pair<mvt_value, serial_val>>(joinkey, std::pair<mvt_value, serial_val>(outval, outsv)));
 								key_order.push_back(joinkey);
@@ -812,7 +815,7 @@ void dispatch_tasks(std::map<zxy, std::vector<std::string>> &tasks, std::vector<
 	}
 
 	for (size_t i = 0; i < CPUS; i++) {
-		if (pthread_create(&pthreads[i], NULL, join_worker, &args[i]) != 0) {
+		if (thread_create(&pthreads[i], NULL, join_worker, &args[i]) != 0) {
 			perror("pthread_create");
 			exit(EXIT_PTHREAD);
 		}