ADD: New settings allow city growth factors to be determined by relat…

…ive rather than absolute city size. See the amended simuconf.tab for documentation.

dataobj/settings.cc

@@ -451,6 +451,11 @@ settings_t::settings_t() :
 	max_small_city_size = 1000;
 	max_city_size = 5000;
 
+	// 0 values for these mean that the above absolute threasholds are used instead.
+	// Set values in simuconf.tab to activate this feature.
+	capital_threshold_percentage = 0;
+	city_threshold_percentage = 0;
+
 	power_revenue_factor_percentage=100;
 
 	allow_making_public = true;
@@ -1471,6 +1476,11 @@ void settings_t::rdwr(loadsave_t *file)
 			}
 			file->rdwr_long(capital_threshold_size);
 			file->rdwr_long(city_threshold_size);
+			if (file->get_extended_version() >= 15 || (file->get_extended_version() >= 14 && file->get_extended_revision() >= 15))
+			{
+				file->rdwr_byte(capital_threshold_percentage);
+				file->rdwr_byte(city_threshold_percentage);
+			}
 		}
 
 		if(  file->get_version()>=110001  ) {
@@ -2569,6 +2579,9 @@ void settings_t::parse_simuconf(tabfile_t& simuconf, sint16& disp_width, sint16&
 	capital_threshold_size  = contents.get_int("capital_threshold_size", capital_threshold_size);
 	max_small_city_size  = contents.get_int("max_small_city_size", max_small_city_size);
 	max_city_size  = contents.get_int("max_city_size", max_city_size);
+	capital_threshold_percentage = contents.get_int("capial_threshold_percentage", capital_threshold_percentage);
+	city_threshold_percentage = contents.get_int("city_threshold_percentage", city_threshold_percentage); 
+
 	spacing_shift_mode = contents.get_int("spacing_shift_mode", spacing_shift_mode);
 	spacing_shift_divisor = contents.get_int("spacing_shift_divisor", spacing_shift_divisor);
 

dataobj/settings.h

@@ -619,6 +619,9 @@ class settings_t
 	uint32 max_small_city_size;
 	uint32 max_city_size;
 
+	uint8 capital_threshold_percentage;
+	uint8 city_threshold_percentage;
+
 	// The factor percentage of power revenue
 	// default: 100
 	// @author: Phystam
@@ -1044,6 +1047,11 @@ class settings_t
 	uint32 get_max_city_size() const { return max_city_size; }
 	void set_max_city_size(uint32 value) { max_city_size = value; }
 
+	uint8 get_capital_threshold_percentage() const { return capital_threshold_percentage; }
+	void set_capital_threshold_percentage(uint8 value) { capital_threshold_percentage = value; }
+	uint8 get_city_threshold_percentage() const { return city_threshold_percentage; }
+	void set_city_threshold_percentage(uint8 value) { city_threshold_percentage = value; }
+
 	uint16 get_default_increase_maintenance_after_years(waytype_t wtype) const { return default_increase_maintenance_after_years[wtype]; }
 	void set_default_increase_maintenance_after_years(waytype_t wtype, uint16 value) { default_increase_maintenance_after_years[wtype] = value; }
 	uint32 get_server_frames_ahead() const { return server_frames_ahead; }

gui/settings_stats.cc

@@ -217,6 +217,8 @@ void settings_extended_general_stats_t::init( settings_t *sets )
 
 	INIT_NUM( "city_threshold_size", sets->get_city_threshold_size(), 1000, 100000, gui_numberinput_t::AUTOLINEAR, false );
 	INIT_NUM( "capital_threshold_size", sets->get_capital_threshold_size(), 10000, 1000000, gui_numberinput_t::AUTOLINEAR, false );
+	INIT_NUM( "city_threshold_percentage", sets->get_city_threshold_percentage(), 0, 100, gui_numberinput_t::PLAIN, false);
+	INIT_NUM( "capital_threshold_percentage", sets->get_capital_threshold_percentage(), 0, 100, gui_numberinput_t::PLAIN, false);
 	INIT_NUM( "max_small_city_size", sets->get_max_small_city_size(), 1000, 100000, gui_numberinput_t::AUTOLINEAR, false );
 	INIT_NUM( "max_city_size", sets->get_max_city_size(), 10000, 1000000, gui_numberinput_t::AUTOLINEAR, false );
 	INIT_NUM( "congestion_density_factor", sets->get_congestion_density_factor(), 0, 1024, gui_numberinput_t::AUTOLINEAR, false );
@@ -320,6 +322,8 @@ void settings_extended_general_stats_t::read(settings_t *sets)
 
 	READ_NUM( sets->set_city_threshold_size );
 	READ_NUM( sets->set_capital_threshold_size );
+	READ_NUM( sets->set_city_threshold_percentage );
+	READ_NUM(sets->set_capital_threshold_percentage);
 	READ_NUM( sets->set_max_small_city_size );
 	READ_NUM( sets->set_max_city_size );
 	READ_NUM( sets->set_congestion_density_factor );

simcity.cc

@@ -2912,21 +2912,75 @@ void stadt_t::calc_growth()
 	settings_t const& s = welt->get_settings();
 
 	// smaller towns should grow slower to have villages for a longer time
-	sint32 const weight_factor =
-		get_city_population() < s.get_city_threshold_size() ? welt->get_settings().get_growthfactor_small()  :
-		get_city_population() < s.get_capital_threshold_size() ? welt->get_settings().get_growthfactor_medium() :
-		welt->get_settings().get_growthfactor_large();
+	// New for January 2020: what counts as a "smaller town" can be proportional to the size of towns if threshold percentages are set.
+	sint32 weight_factor; 
+
+	if (s.get_capital_threshold_percentage() == 0 && s.get_city_threshold_percentage() == 0)
+	{
+		// Percentages specified as zero - use the old algorithm
+		weight_factor =
+			get_city_population() < s.get_city_threshold_size() ? welt->get_settings().get_growthfactor_small() :
+			get_city_population() < s.get_capital_threshold_size() ? welt->get_settings().get_growthfactor_medium() :
+			s.get_growthfactor_large();
+	}
+	else
+	{
+		// It is possible that only one threshold percentage is set. In this case, assume the other.
+		uint8 capital_threshold_percentage = s.get_capital_threshold_percentage() ? s.get_capital_threshold_percentage() : s.get_city_threshold_percentage() / 4;
+		capital_threshold_percentage = capital_threshold_percentage ? capital_threshold_percentage : 1;
+		uint8 city_threshold_percentage = s.get_city_threshold_percentage() ? s.get_city_threshold_percentage() : capital_threshold_percentage * 4; 
+
+		// Now that we have the percentages, calculate how large that this city is compared to others in the game.
+		uint32 number_of_larger_cities = 0;
+		uint32 number_of_smaller_cities = 0;
+		FOR(const weighted_vector_tpl<stadt_t*>, const& city, welt->get_cities())
+		{
+			if (city == this)
+			{
+				continue;
+			}
+			if (city->get_city_population() > get_city_population())
+			{
+				number_of_larger_cities++;
+			}
+			else
+			{
+				number_of_smaller_cities++;
+			}
+		}
+
+		const uint32 total_cities = number_of_larger_cities + number_of_smaller_cities + 1;
+		const uint32 rank = number_of_larger_cities + 1;
+		const uint32 percentage = (rank * 100) / total_cities; 
+
+		if (rank == 1 || percentage <= s.get_capital_threshold_percentage())
+		{
+			weight_factor = s.get_growthfactor_large();
+		}
+		else if (percentage <= s.get_city_threshold_percentage())
+		{
+			weight_factor = s.get_growthfactor_medium();
+		}
+		else
+		{
+			weight_factor = s.get_growthfactor_small();
+		}
+	}
 
 	// now compute the growth for this step
 	sint32 growth_factor = weight_factor > 0 ? total_supply_percentage / weight_factor : 0;
 
+	// Formerly, congestion directly affected growth. However, this is not realistic: it should only
+	// affect growth indirectly by reducing the proportion of successful journeys. In any event,
+	// the percentage now has a new meaning: the percentage by which car journeys are slowed down.
+#if 0
 	// Congestion adversely impacts on growth. At 100% congestion, there will be no growth.
 	if(city_history_month[0][HIST_CONGESTION] > 0)
 	{
 		const uint32 congestion_factor = city_history_month[0][HIST_CONGESTION];
 		growth_factor -= (congestion_factor * growth_factor) / 100;
 	}
-
+#endif
 	// Scale up growth to have a larger fractional component. This allows small growth units to accumulate in the case of long months.
 	sint64 new_unsupplied_city_growth = (sint64)growth_factor * (CITYGROWTH_PER_CITICEN / 16ll);
 

simutrans/config/simuconf.tab

@@ -164,6 +164,34 @@ growthfactor_villages = 400
 growthfactor_cities = 200
 growthfactor_capitals = 100
 
+# The rate at which towns grow depends on their size. There are three different size categories:
+# "Villages", "Cities" and "Capitals". The following settings define the thresholds (in numbers 
+# of population) above which towns become "Cities" and "Capitals". Anything smaller than 
+# city_threshold_size is a "Village". These settings are overriden if any value in 
+# city_threshold_percentage or capital_threshold_percentage be set. 
+
+city_threshold_size = 2500
+capital_threshold_size = 25000
+
+# These values determine which rates of town growth apply depending, not on the absolute size
+# of the city, but rather its size relative to other cities in the game. If capital_threshold_percentage
+# is 5, for example, any city in the top 5% of cities by population count will be a capital. 
+# These settings override the absolute values in city_threshold_size and capital_threshold_size
+# unless their values are 0, which is the default. It is recommended to use these rather than absolute
+# values, especially in longer games, where all towns may grow to the size of "capitals" eventually.
+
+city_threshold_percentage = 20
+capital_threshold_percentage = 2
+
+# These values are used in the city generation algorithm to determine the maximum size of cities.
+# max_city_size is the maximum size, in citizens, of any city at the point of generation.
+# max_small_city_size is the size, in citizens, of any city other than a "big city" at the point of generation. 
+#
+# TIP: Set a lower number for these values the earlier that the game is started.
+
+max_city_size = 20000
+max_small_city_size = 3000
+
 # Enable this to use the old algorithm for city growth from Standard.
 # NOTE: The renovation_percentage in cityrules.tab should be increased if this be done.
 quick_city_growth = 0

simversion.h

@@ -28,8 +28,8 @@ extern "C" FILE * __cdecl __iob_func(void) { return _iob; }
 #define SIM_SERVER_MINOR    4
 
 #define EX_VERSION_MAJOR	14
-#define EX_VERSION_MINOR	5
-#define EX_SAVE_MINOR		14
+#define EX_VERSION_MINOR	6
+#define EX_SAVE_MINOR		15
 
 // Do not forget to increment the save game versions in settings_stats.cc when changing this