[MIRROR] Optimizations for reactions [MDB IGNORE] (#25788)

* Optimizations for reactions (#80380)

## About The Pull Request
1. Fixes #80365

The lowers the rounding accuracy for reaction rate from
`CHEMICAL_VOLUME_ROUNDING(0.01)` to
`CHEMICAL_QUANTIZATION_LEVEL(0.0001)`. This stops reactions from
abruptly ending when either their temperature/ph/volume become very low
values.

This also removes a call to `handle_reactions()` after the reaction has
finished so it that it doesn't restart reactions that have failed due to
failed environmental conditions(low ph/temps far below the optimal
value). This not only saves overhead but can also stop potential
infinite reaction loops(where if a reaction fails we try to restart it
again)

2. Simplifies math for temperature handling and stops each react step
from calling `handle_reactions()` when new reagent products are formed
thus making reactions slightly faster. Also ensures early return if
adding/removing reagents failed at any point & other smaller. nitpicks

3. Removes excess call to `update_total()` in each react step making it
even faster

## Changelog
🆑
fix: Reactions whose temps/ph values fall way below their optimal values
no longer restart & prevents infinite loops. Made reaction code slightly
faster
/🆑

* Optimizations for reactions

---------

Co-authored-by: SyncIt21 <110812394+SyncIt21@users.noreply.github.com>

code/modules/reagents/chemistry/equilibrium.dm

@@ -168,7 +168,7 @@
 	step_target_vol = 0
 	reacted_vol = 0 //Because volumes can be lost mid reactions
 	for(var/product in reaction.results)
-		step_target_vol += (multiplier * reaction.results[product])
+		step_target_vol += multiplier * reaction.results[product]
 		reacted_vol += holder.get_reagent_amount(product)
 	target_vol = reacted_vol + step_target_vol
 	return TRUE
@@ -277,7 +277,7 @@
 	//Calculate DeltaT (Deviation of T from optimal)
 	if(!reaction.is_cold_recipe)
 		if (cached_temp < reaction.optimal_temp && cached_temp >= reaction.required_temp)
-			delta_t = (((cached_temp - reaction.required_temp) ** reaction.temp_exponent_factor) / ((reaction.optimal_temp - reaction.required_temp) ** reaction.temp_exponent_factor))
+			delta_t = ((cached_temp - reaction.required_temp) / (reaction.optimal_temp - reaction.required_temp)) ** reaction.temp_exponent_factor
 		else if (cached_temp >= reaction.optimal_temp)
 			delta_t = 1
 		else //too hot
@@ -286,7 +286,7 @@
 			return
 	else
 		if (cached_temp > reaction.optimal_temp && cached_temp <= reaction.required_temp)
-			delta_t = (((reaction.required_temp - cached_temp) ** reaction.temp_exponent_factor) / ((reaction.required_temp - reaction.optimal_temp) ** reaction.temp_exponent_factor))
+			delta_t = ((reaction.required_temp - cached_temp) / (reaction.required_temp - reaction.optimal_temp)) ** reaction.temp_exponent_factor
 		else if (cached_temp <= reaction.optimal_temp)
 			delta_t = 1
 		else //Too cold
@@ -312,34 +312,39 @@
 	purity *= purity_modifier
 
 	//Now we calculate how much to add - this is normalised to the rate up limiter
-	var/delta_chem_factor = (reaction.rate_up_lim * delta_t) * seconds_per_tick//add/remove factor
+	var/delta_chem_factor = reaction.rate_up_lim * delta_t * seconds_per_tick//add/remove factor
 	//keep limited
 	if(delta_chem_factor > step_target_vol)
 		delta_chem_factor = step_target_vol
 	//Normalise to multiproducts
-	delta_chem_factor = round(delta_chem_factor / product_ratio, CHEMICAL_VOLUME_ROUNDING)
+	delta_chem_factor = round(delta_chem_factor / product_ratio, CHEMICAL_QUANTISATION_LEVEL)
 	if(delta_chem_factor <= 0)
 		to_delete = TRUE
 		return
 
 	//Calculate how much product to make and how much reactant to remove factors..
-	for(var/reagent in reaction.required_reagents)
-		holder.remove_reagent(reagent, (delta_chem_factor * reaction.required_reagents[reagent]))
+	var/required_amount
+	for(var/datum/reagent/requirement as anything in reaction.required_reagents)
+		required_amount = reaction.required_reagents[requirement]
+		if(!holder.remove_reagent(requirement, delta_chem_factor * required_amount))
+			to_delete = TRUE
+			return
 		//Apply pH changes
 		var/pH_adjust
 		if(reaction.reaction_flags & REACTION_PH_VOL_CONSTANT)
-			pH_adjust = ((delta_chem_factor * reaction.required_reagents[reagent]) / target_vol) * (reaction.H_ion_release * h_ion_mod)
+			pH_adjust = ((delta_chem_factor * required_amount) / target_vol) * (reaction.H_ion_release * h_ion_mod)
 		else //Default adds pH independant of volume
-			pH_adjust = (delta_chem_factor * reaction.required_reagents[reagent]) * (reaction.H_ion_release * h_ion_mod)
-		holder.adjust_specific_reagent_ph(reagent, pH_adjust)
+			pH_adjust = (delta_chem_factor * required_amount) * (reaction.H_ion_release * h_ion_mod)
+		holder.adjust_specific_reagent_ph(requirement, pH_adjust)
 
 	var/step_add
 	var/total_step_added = 0
-	for(var/product in reaction.results)
+	for(var/datum/reagent/product as anything in reaction.results)
 		//create the products
-		step_add = delta_chem_factor * reaction.results[product]
-		//Default handiling
-		holder.add_reagent(product, step_add, null, cached_temp, purity, override_base_ph = TRUE)
+		step_add = holder.add_reagent(product, delta_chem_factor * reaction.results[product], null, cached_temp, purity, override_base_ph = TRUE, no_react = TRUE)
+		if(!step_add)
+			to_delete = TRUE
+			return
 
 		//Apply pH changes
 		var/pH_adjust
@@ -348,6 +353,8 @@
 		else
 			pH_adjust = step_add * (reaction.H_ion_release * h_ion_mod)
 		holder.adjust_specific_reagent_ph(product, pH_adjust)
+
+		//record amounts created
 		reacted_vol += step_add
 		total_step_added += step_add
 
@@ -377,14 +384,13 @@
 	//post reaction checks
 	if(!(check_fail_states(total_step_added)))
 		to_delete = TRUE
+		return
 
 	//end reactions faster so plumbing is faster
 	//length is so that plumbing is faster - but it doesn't disable competitive reactions. Basically, competitive reactions will likely reach their step target at the start, so this will disable that. We want to avoid that. But equally, we do want to full stop a holder from reacting asap so plumbing isn't waiting an tick to resolve.
-	if((step_add >= step_target_vol) && (length(holder.reaction_list == 1)))
+	if((step_add >= step_target_vol) && (length(holder.reaction_list) == 1))
 		to_delete = TRUE
 
-	holder.update_total()
-
 /*
 * Calculates the total sum normalised purity of ALL reagents in a holder
 * Currently calculates it irrespective of required reagents at the start, but this should be changed if this is powergamed to required reagents

code/modules/reagents/chemistry/holder/holder.dm

@@ -643,7 +643,7 @@
 		reagent_volume = round(reagent.volume, CHEMICAL_QUANTISATION_LEVEL) //round to this many decimal places
 
 		//remove very small amounts of reagents
-		if((reagent_volume <= 0.05 && !is_reacting) || reagent_volume <= CHEMICAL_QUANTISATION_LEVEL)
+		if(!reagent_volume || (reagent_volume <= 0.05 && !is_reacting))
 			//end metabolization
 			if(isliving(my_atom))
 				if(reagent.metabolizing)
@@ -663,14 +663,14 @@
 
 		//compute volume & ph like we would normally
 		. += reagent_volume
-		total_ph += (reagent.ph * reagent_volume)
+		total_ph += reagent.ph * reagent_volume
 
 		//reasign rounded value
 		reagent.volume = reagent_volume
 
 	//assign the final values, rounding up can sometimes cause overflow so bring it down
 	total_volume = min(round(., CHEMICAL_VOLUME_ROUNDING), maximum_volume)
-	if(!.)
+	if(!total_volume)
 		ph = CHEMICAL_NORMAL_PH
 	else
 		ph = clamp(total_ph / total_volume, CHEMICAL_MIN_PH, CHEMICAL_MAX_PH)

code/modules/reagents/chemistry/holder/properties.dm

@@ -32,7 +32,7 @@
 
 		//short cut to break when we have found our one exact type
 		if(type_check == REAGENT_STRICT_TYPE)
-			break
+			return total_amount
 
 	return round(total_amount, CHEMICAL_VOLUME_ROUNDING)
 

code/modules/reagents/chemistry/holder/reactions.dm

@@ -236,8 +236,6 @@
 	is_reacting = FALSE
 	LAZYNULL(previous_reagent_list) //reset it to 0 - because any change will be different now.
 	update_total()
-	if(!QDELING(src))
-		handle_reactions() //Should be okay without. Each step checks.
 
 /*
 * Force stops the current holder/reagents datum from reacting