porting CEV-Eris pickweight procs.

code/__HELPERS/_lists.dm

@@ -231,40 +231,77 @@
 
 //Picks a random element from a list based on a weighting system:
 //1. Adds up the total of weights for each element
-//2. Gets a number between 1 and that total
+//2. Gets the total from 0% to 100% of previous total value.
 //3. For each element in the list, subtracts its weighting from that number
 //4. If that makes the number 0 or less, return that element.
-/proc/pickweight(list/L)
+/proc/pickweight(list/L, base_weight = 1)
 	var/total = 0
 	var/item
 	for (item in L)
 		if (!L[item])
-			L[item] = 1
+			L[item] = base_weight
 		total += L[item]
 
-	total = rand(1, total)
+	total = rand() * total
 	for (item in L)
-		total -=L [item]
+		total -= L[item]
 		if (total <= 0)
 			return item
 
-	return null
-
-/proc/pickweightAllowZero(list/L) //The original pickweight proc will sometimes pick entries with zero weight.  I'm not sure if changing the original will break anything, so I left it be.
+//Picks a number of elements from a list based on weight.
+//This is highly optimised and good for things like grabbing 200 items from a list of 40,000
+//Much more efficient than many pickweight calls
+/proc/pickweight_mult(list/L, quantity, base_weight = 1)
+	//First we total the list as normal
 	var/total = 0
 	var/item
 	for (item in L)
 		if (!L[item])
-			L[item] = 0
+			L[item] = base_weight
 		total += L[item]
 
-	total = rand(0, total)
-	for (item in L)
-		total -=L [item]
-		if (total <= 0 && L[item])
-			return item
+	//Next we will make a list of randomly generated numbers, called Requests
+	//It is critical that this list be sorted in ascending order, so we will build it in that order
+	//First one is free, so we start counting at 2
+	var/list/requests = list(rand(1, total))
+	for (var/i in 2 to quantity)
+		//Each time we generate the next request
+		var/newreq = rand()* total
+		//We will loop through all existing requests
+		for (var/j in 1 to requests.len)
+			//We keep going through the list until we find an element which is bigger than the one we want to add
+			if (requests[j] > newreq)
+				//And then we insert the newqreq at that point, pushing everything else forward
+				requests.Insert(j, newreq)
+				break
 
-	return null
+
+
+	//Now when we get here, we have a list of random numbers sorted in ascending order.
+	//The length of that list is equal to Quantity passed into this function
+	//Next we make a list to store results
+	var/list/results = list()
+
+	//Zero the total, we'll reuse it
+	total = 0
+
+	//Now we will iterate forward through the items list, adding each weight to the total
+	for (item in L)
+		total += L[item]
+
+		//After each item we do a while loop
+		while (requests.len && total >= requests[1])
+			//If the total is higher than the value of the first request
+			results += item //We add this item to the results list
+			requests.Cut(1,2) //And we cut off the top of the requests list
+
+			//This while loop will repeat until the next request is higher than the total.
+			//The current item might be added to the results list many times, in this process
+
+	//By the time we get here:
+		//Requests will be empty
+		//Results will have a length of quality
+	return results
 
 //Pick a random element from the list and remove it from the list.
 /proc/pick_n_take(list/L)
@@ -274,6 +311,13 @@
 		. = L[picked]
 		L.Cut(picked,picked+1)			//Cut is far more efficient that Remove()
 
+//Pick a random element from the list by weight and remove it from the list.
+//Result is returned as a list in the format list(key, value)
+/proc/pickweight_n_take(list/L, base_weight = 1)
+	if (L.len)
+		. = pickweight(L, base_weight)
+		L.Remove(.)
+
 //Returns the top(last) element from the list and removes it from the list (typical stack function)
 /proc/pop(list/L)
 	if(L.len)

code/controllers/subsystem/vote.dm

@@ -361,7 +361,7 @@ SUBSYSTEM_DEF(vote)
 						picked = S
 					runnable_storytellers[S] *= round(stored_gamemode_votes[initial(S.name)]*100000,1)
 				if(!picked)
-					picked = pickweightAllowZero(runnable_storytellers)
+					picked = pickweight(runnable_storytellers, 0)
 				GLOB.dynamic_storyteller_type = picked
 			if("map")
 				var/datum/map_config/VM = config.maplist[.]

code/datums/ai_laws.dm

@@ -253,7 +253,7 @@
 	var/datum/ai_laws/lawtype
 	var/list/law_weights = CONFIG_GET(keyed_list/law_weight)
 	while(!lawtype && law_weights.len)
-		var/possible_id = pickweightAllowZero(law_weights)
+		var/possible_id = pickweight(law_weights, 0)
 		lawtype = lawid_to_type(possible_id)
 		if(!lawtype)
 			law_weights -= possible_id

code/game/gamemodes/game_mode.dm

@@ -272,7 +272,7 @@
 		reports += config.mode_reports[config_tag]
 		Count++
 	for(var/i in Count to rand(3,5)) //Between three and five wrong entries on the list.
-		var/false_report_type = pickweightAllowZero(report_weights)
+		var/false_report_type = pickweight(report_weights, 0)
 		report_weights[false_report_type] = 0 //Make it so the same false report won't be selected twice
 		reports += config.mode_reports[false_report_type]
 

code/game/objects/effects/landmarks.dm

@@ -483,7 +483,7 @@ INITIALIZE_IMMEDIATE(/obj/effect/landmark/start/new_player)
 			if(!SSmapping.station_room_templates[t])
 				log_world("Station room spawner placed at ([T.x], [T.y], [T.z]) has invalid ruin name of \"[t]\" in its list")
 				templates -= t
-		template_name = pickweightAllowZero(templates)
+		template_name = pickweight(templates, 0)
 	if(!template_name)
 		GLOB.stationroom_landmarks -= src
 		qdel(src)

code/modules/antagonists/traitor/datum_traitor.dm

@@ -48,7 +48,7 @@
 			var/datum/traitor_class/class = GLOB.traitor_classes[C]
 			var/weight = LOGISTIC_FUNCTION(1.5*class.weight,chaos_weight,class.chaos,0)
 			weights[C] = weight * 1000
-	var/choice = pickweightAllowZero(weights)
+	var/choice = pickweight(weights, 0)
 	if(!choice)
 		choice = TRAITOR_HUMAN // it's an "easter egg"
 	var/datum/traitor_class/actual_class = GLOB.traitor_classes[choice]