From cc850bf7998daa0d785facaca59f89ec2aab6225 Mon Sep 17 00:00:00 2001
From: "Somhairle H. Marisol" <muqiu-han@outlook.com>
Date: Mon, 21 Sep 2026 23:53:40 +0800
Subject: perf(sim): M6a 谣言窗口扫描去中间表——最新在前早停递归替代
 takeWhile/filter/sort，零分配且等价
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---
 src/LivingVillage.Kernel/Sim.fs | 44 +++++++++++++++++++++++------------------
 1 file changed, 25 insertions(+), 19 deletions(-)

diff --git a/src/LivingVillage.Kernel/Sim.fs b/src/LivingVillage.Kernel/Sim.fs
index fd50fed..cedadfa 100644
--- a/src/LivingVillage.Kernel/Sim.fs
+++ b/src/LivingVillage.Kernel/Sim.fs
@@ -685,17 +685,18 @@ module Sim =
         trimRumors nowTick (rumor :: rumors)
 
     let private latestRumorFor (receiver: NpcId) (world: World) : RumorEvent option =
-        // 工作集最新在前且 Tick 非递增，故只需扫描新鲜窗口；窗口外条目本就会被过滤掉。
-        world.Rumors
-        |> List.takeWhile (fun rumor -> world.Tick - rumor.Tick <= rumorFreshnessTicks)
-        |> List.filter (fun rumor ->
-            rumor.Receiver = receiver
-            && rumor.Tick <= world.Tick
-            && rumorStrengthAt world.Tick rumor >= rumorMinimumStrength)
-        |> List.sortByDescending (fun rumor ->
-            let (RumorId id) = rumor.Id
-            rumor.Tick, id)
-        |> List.tryHead
+        // 工作集最新在前且 Tick 非递增：第一条命中的即“Tick 最大、Id 最大”，与原实现
+        // （filter 后 sortByDescending 取头）等价；窗口外无分配提前返回。
+        let rec loop (rest: RumorEvent list) : RumorEvent option =
+            match rest with
+            | [] -> None
+            | rumor :: tail ->
+                if world.Tick - rumor.Tick > rumorFreshnessTicks then None
+                elif rumor.Receiver = receiver
+                     && rumor.Tick <= world.Tick
+                     && rumorStrengthAt world.Tick rumor >= rumorMinimumStrength then Some rumor
+                else loop tail
+        loop world.Rumors
 
     /// 工作集最新在前，头节点恒为最大 Id（每次追加 `max+1`），故 O(1) 取下一个 Id。
     /// 裁剪只丢尾部旧条目，不会丢头，因此该不变量在裁剪后仍成立。
@@ -826,14 +827,19 @@ module Sim =
 
     let private rumorIsDuplicate (request: ChatRequest) (parent: RumorEvent option) (world: World) : bool =
         let parentId = parent |> Option.map (fun rumor -> rumor.Id)
-        world.Rumors
-        |> List.takeWhile (fun rumor -> world.Tick - rumor.Tick <= rumorFreshnessTicks)
-        |> List.exists (fun rumor ->
-            rumor.Narrator = request.Narrator
-            && rumor.Receiver = request.Receiver
-            && rumor.Parent = parentId
-            && rumor.Tick <= world.Tick
-            && rumorStrengthAt world.Tick rumor >= rumorMinimumStrength)
+        // 窗口外条目强度必 < rumorMinimumStrength，与原全表 exists 等价；命中或越窗即无分配返回。
+        let rec loop (rest: RumorEvent list) : bool =
+            match rest with
+            | [] -> false
+            | rumor :: tail ->
+                if world.Tick - rumor.Tick > rumorFreshnessTicks then false
+                elif rumor.Narrator = request.Narrator
+                     && rumor.Receiver = request.Receiver
+                     && rumor.Parent = parentId
+                     && rumor.Tick <= world.Tick
+                     && rumorStrengthAt world.Tick rumor >= rumorMinimumStrength then true
+                else loop tail
+        loop world.Rumors
 
     type private ChatParticipant =
         | AvatarParticipant
-- 
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