将股票持仓盈亏切换为定点批次账本

crates/fidc-core/src/platform_expr_strategy.rs

@@ -10069,12 +10069,12 @@ impl PlatformExprStrategy {
             equity: market_value,
             value_percent,
             unrealized_pnl: position.unrealized_pnl(),
-            realized_pnl: position.realized_pnl,
+            realized_pnl: position.realized_pnl(),
             pnl: position.pnl(),
             day_trade_quantity_delta: position.day_trade_quantity_delta() as i64,
             trading_pnl: position.trading_pnl,
             position_pnl: position.position_pnl,
-            dividend_receivable: position.dividend_receivable,
+            dividend_receivable: position.dividend_receivable(),
         };
         let stop_hit = if self.config.stop_loss_expr.trim().is_empty() {
             false

crates/fidc-core/src/portfolio.rs

@@ -6,35 +6,78 @@ use std::collections::{BTreeMap, BTreeSet};
 use crate::data::{DataSet, DataSetError, PriceField};
 use crate::fixed_point::{FixedMoney, MONEY_SCALE};
 
+fn fixed_money(value: f64, label: &str) -> Result<FixedMoney, String> {
+    FixedMoney::from_f64(value)
+        .ok_or_else(|| format!("{label} is not representable as fixed-point money: {value}"))
+}
+
+fn fixed_money_or_panic(value: f64, label: &str) -> FixedMoney {
+    fixed_money(value, label).unwrap_or_else(|error| panic!("{error}"))
+}
+
+fn allocate_fixed_value(
+    total: FixedMoney,
+    allocated_quantity: u32,
+    total_quantity: u32,
+) -> Result<FixedMoney, String> {
+    if allocated_quantity > total_quantity || total_quantity == 0 {
+        return Err("invalid fixed-point lot allocation quantity".to_string());
+    }
+    if allocated_quantity == total_quantity {
+        return Ok(total);
+    }
+    let product = total
+        .raw()
+        .checked_mul(i128::from(allocated_quantity))
+        .ok_or_else(|| "fixed-point lot allocation overflow".to_string())?;
+    let divisor = i128::from(total_quantity);
+    let quotient = product / divisor;
+    let remainder = product % divisor;
+    let rounded = if remainder
+        .checked_abs()
+        .and_then(|value| value.checked_mul(2))
+        .is_some_and(|value| value >= divisor)
+    {
+        quotient
+            .checked_add(product.signum())
+            .ok_or_else(|| "fixed-point lot allocation overflow".to_string())?
+    } else {
+        quotient
+    };
+    Ok(FixedMoney::from_raw(rounded))
+}
+
 #[derive(Debug, Clone)]
 pub struct PositionLot {
     pub acquired_date: NaiveDate,
     pub quantity: u32,
-    pub entry_price: f64,
+    // Total values keep partial-lot allocation exact without a rounded per-share mirror.
-    pub price: f64,
+    entry_value: FixedMoney,
+    cost_basis: FixedMoney,
 }
 
 #[derive(Debug, Clone)]
 pub struct Position {
     pub symbol: String,
     pub quantity: u32,
+    // ALV-compatible moving average including buy costs; partial sells do not rebase it.
     pub average_cost: f64,
     pub last_price: f64,
-    pub realized_pnl: f64,
+    realized_pnl: FixedMoney,
-    realized_entry_pnl: f64,
+    realized_entry_pnl: FixedMoney,
     pub trading_pnl: f64,
     pub position_pnl: f64,
-    pub dividend_receivable: f64,
+    dividend_receivable: FixedMoney,
     day_start_quantity: u32,
     day_start_price: f64,
     day_split_ratio: f64,
-    day_dividend_cash: f64,
+    day_dividend_cash: FixedMoney,
     day_trade_quantity_delta: i32,
-    day_trade_cost: f64,
+    day_trade_cost: FixedMoney,
     day_buy_quantity: u32,
     day_sell_quantity: u32,
-    day_buy_value: f64,
+    day_buy_value: FixedMoney,
-    day_sell_value: f64,
+    day_sell_value: FixedMoney,
     lots: Vec<PositionLot>,
 }
 
@@ -45,21 +88,21 @@ impl Position {
             quantity: 0,
             average_cost: 0.0,
             last_price: 0.0,
-            realized_pnl: 0.0,
+            realized_pnl: FixedMoney::ZERO,
-            realized_entry_pnl: 0.0,
+            realized_entry_pnl: FixedMoney::ZERO,
             trading_pnl: 0.0,
             position_pnl: 0.0,
-            dividend_receivable: 0.0,
+            dividend_receivable: FixedMoney::ZERO,
             day_start_quantity: 0,
             day_start_price: 0.0,
             day_split_ratio: 1.0,
-            day_dividend_cash: 0.0,
+            day_dividend_cash: FixedMoney::ZERO,
             day_trade_quantity_delta: 0,
-            day_trade_cost: 0.0,
+            day_trade_cost: FixedMoney::ZERO,
             day_buy_quantity: 0,
             day_sell_quantity: 0,
-            day_buy_value: 0.0,
+            day_buy_value: FixedMoney::ZERO,
-            day_sell_value: 0.0,
+            day_sell_value: FixedMoney::ZERO,
             lots: Vec::new(),
         }
     }
@@ -85,17 +128,24 @@ impl Position {
 
         let previous_quantity = self.quantity;
         let previous_average_cost = self.average_cost;
+        let gross_amount = fixed_money_or_panic(
+            execution_price * quantity as f64,
+            "position buy gross amount",
+        );
         self.lots.push(PositionLot {
             acquired_date: date,
             quantity,
-            entry_price: execution_price,
+            entry_value: gross_amount,
-            price: execution_price,
+            cost_basis: gross_amount,
         });
         self.quantity += quantity;
         self.last_price = normalized_mark_price(mark_price, execution_price);
         self.day_trade_quantity_delta += quantity as i32;
         self.day_buy_quantity += quantity;
-        self.day_buy_value += execution_price * quantity as f64;
+        self.day_buy_value = self
+            .day_buy_value
+            .checked_add(gross_amount)
+            .expect("fixed-point day buy value overflow");
         if previous_quantity > 0
             && previous_average_cost.is_finite()
             && previous_average_cost > 0.0
@@ -128,9 +178,14 @@ impl Position {
             ));
         }
 
+        let total_proceeds = fixed_money(
+            execution_price * quantity as f64,
+            "position sell gross amount",
+        )?;
         let mut remaining = quantity;
-        let mut realized = 0.0;
+        let mut remaining_proceeds = total_proceeds;
-        let mut realized_entry = 0.0;
+        let mut realized = FixedMoney::ZERO;
+        let mut realized_entry = FixedMoney::ZERO;
         let average_cost_before_sell = self.average_cost;
 
         while remaining > 0 {
@@ -138,9 +193,38 @@ impl Position {
                 return Err(format!("position {} has no lots to sell", self.symbol));
             };
 
-            let lot_sell = remaining.min(first_lot.quantity);
+            let lot_quantity_before = first_lot.quantity;
-            realized += (execution_price - first_lot.price) * lot_sell as f64;
+            let lot_sell = remaining.min(lot_quantity_before);
-            realized_entry += (execution_price - first_lot.entry_price) * lot_sell as f64;
+            let lot_proceeds = allocate_fixed_value(remaining_proceeds, lot_sell, remaining)?;
+            let lot_cost =
+                allocate_fixed_value(first_lot.cost_basis, lot_sell, lot_quantity_before)?;
+            let lot_entry =
+                allocate_fixed_value(first_lot.entry_value, lot_sell, lot_quantity_before)?;
+            realized = realized
+                .checked_add(
+                    lot_proceeds
+                        .checked_sub(lot_cost)
+                        .ok_or_else(|| "fixed-point realized PnL overflow".to_string())?,
+                )
+                .ok_or_else(|| "fixed-point realized PnL overflow".to_string())?;
+            realized_entry = realized_entry
+                .checked_add(
+                    lot_proceeds
+                        .checked_sub(lot_entry)
+                        .ok_or_else(|| "fixed-point realized entry PnL overflow".to_string())?,
+                )
+                .ok_or_else(|| "fixed-point realized entry PnL overflow".to_string())?;
+            first_lot.cost_basis = first_lot
+                .cost_basis
+                .checked_sub(lot_cost)
+                .ok_or_else(|| "fixed-point lot cost underflow".to_string())?;
+            first_lot.entry_value = first_lot
+                .entry_value
+                .checked_sub(lot_entry)
+                .ok_or_else(|| "fixed-point lot entry underflow".to_string())?;
+            remaining_proceeds = remaining_proceeds
+                .checked_sub(lot_proceeds)
+                .ok_or_else(|| "fixed-point sell proceeds underflow".to_string())?;
             first_lot.quantity -= lot_sell;
             remaining -= lot_sell;
 
@@ -151,11 +235,20 @@ impl Position {
 
         self.quantity -= quantity;
         self.last_price = normalized_mark_price(mark_price, execution_price);
-        self.realized_pnl += realized;
+        self.realized_pnl = self
-        self.realized_entry_pnl += realized_entry;
+            .realized_pnl
+            .checked_add(realized)
+            .ok_or_else(|| "fixed-point realized PnL overflow".to_string())?;
+        self.realized_entry_pnl = self
+            .realized_entry_pnl
+            .checked_add(realized_entry)
+            .ok_or_else(|| "fixed-point realized entry PnL overflow".to_string())?;
         self.day_trade_quantity_delta -= quantity as i32;
         self.day_sell_quantity += quantity;
-        self.day_sell_value += execution_price * quantity as f64;
+        self.day_sell_value = self
+            .day_sell_value
+            .checked_add(total_proceeds)
+            .ok_or_else(|| "fixed-point day sell value overflow".to_string())?;
         if self.quantity == 0 {
             self.recalculate_average_cost();
         } else if average_cost_before_sell.is_finite() && average_cost_before_sell > 0.0 {
@@ -164,7 +257,7 @@ impl Position {
             self.recalculate_average_cost();
         }
         self.refresh_day_pnl();
-        Ok(realized)
+        Ok(realized.to_f64())
     }
 
     pub fn sellable_qty(&self, date: NaiveDate) -> u32 {
@@ -180,22 +273,49 @@ impl Position {
     }
 
     pub fn unrealized_pnl(&self) -> f64 {
-        (self.last_price - self.average_cost) * self.quantity as f64
+        if self.quantity == 0 {
+            return 0.0;
+        }
+        fixed_money_or_panic(
+            self.last_price * self.quantity as f64,
+            "position marked value",
+        )
+        .checked_sub(self.total_cost_basis())
+        .expect("fixed-point unrealized PnL overflow")
+        .to_f64()
     }
 
     pub fn unrealized_entry_pnl(&self) -> f64 {
-        let Some(avg_price) = self.average_entry_price() else {
+        if self.quantity == 0 {
             return 0.0;
-        };
+        }
-        (self.last_price - avg_price) * self.quantity as f64
+        fixed_money_or_panic(
+            self.last_price * self.quantity as f64,
+            "position marked value",
+        )
+        .checked_sub(self.total_entry_value())
+        .expect("fixed-point unrealized entry PnL overflow")
+        .to_f64()
     }
 
     pub fn pnl(&self) -> f64 {
-        self.realized_pnl + self.unrealized_pnl()
+        self.realized_pnl.to_f64() + self.unrealized_pnl()
     }
 
     pub fn entry_pnl(&self) -> f64 {
-        self.realized_entry_pnl + self.unrealized_entry_pnl()
+        self.realized_entry_pnl.to_f64() + self.unrealized_entry_pnl()
+    }
+
+    pub fn realized_pnl(&self) -> f64 {
+        self.realized_pnl.to_f64()
+    }
+
+    pub fn realized_entry_pnl(&self) -> f64 {
+        self.realized_entry_pnl.to_f64()
+    }
+
+    pub fn dividend_receivable(&self) -> f64 {
+        self.dividend_receivable.to_f64()
     }
 
     pub fn day_start_quantity(&self) -> u32 {
@@ -215,18 +335,18 @@ impl Position {
     }
 
     pub fn bought_value(&self) -> f64 {
-        self.day_buy_value
+        self.day_buy_value.to_f64()
     }
 
     pub fn sold_value(&self) -> f64 {
-        self.day_sell_value
+        self.day_sell_value.to_f64()
     }
 
     pub fn buy_avg_price(&self) -> f64 {
         if self.day_buy_quantity == 0 {
             0.0
         } else {
-            self.day_buy_value / self.day_buy_quantity as f64
+            self.day_buy_value.to_f64() / self.day_buy_quantity as f64
         }
     }
 
@@ -234,31 +354,34 @@ impl Position {
         if self.day_sell_quantity == 0 {
             0.0
         } else {
-            self.day_sell_value / self.day_sell_quantity as f64
+            self.day_sell_value.to_f64() / self.day_sell_quantity as f64
         }
     }
 
     pub fn transaction_cost(&self) -> f64 {
-        self.day_trade_cost
+        self.day_trade_cost.to_f64()
     }
 
     pub fn begin_trading_day(&mut self) {
         self.day_start_quantity = self.quantity;
         self.day_start_price = self.last_price;
         self.day_split_ratio = 1.0;
-        self.day_dividend_cash = 0.0;
+        self.day_dividend_cash = FixedMoney::ZERO;
         self.day_trade_quantity_delta = 0;
-        self.day_trade_cost = 0.0;
+        self.day_trade_cost = FixedMoney::ZERO;
         self.day_buy_quantity = 0;
         self.day_sell_quantity = 0;
-        self.day_buy_value = 0.0;
+        self.day_buy_value = FixedMoney::ZERO;
-        self.day_sell_value = 0.0;
+        self.day_sell_value = FixedMoney::ZERO;
         self.refresh_day_pnl();
     }
 
     pub fn record_trade_cost(&mut self, value: f64) {
         if value.is_finite() {
-            self.day_trade_cost += value.max(0.0);
+            self.day_trade_cost = self
+                .day_trade_cost
+                .checked_add(fixed_money_or_panic(value.max(0.0), "position trade cost"))
+                .expect("fixed-point day trade cost overflow");
             self.refresh_day_pnl();
         }
     }
@@ -267,27 +390,33 @@ impl Position {
         if quantity == 0 || !value.is_finite() {
             return;
         }
-        let cost = value.max(0.0);
+        let cost = fixed_money_or_panic(value.max(0.0), "position buy trade cost");
-        if cost <= 0.0 {
+        if cost.raw() <= 0 {
             return;
         }
         if let Some(lot) = self.lots.last_mut() {
-            lot.price += cost / quantity as f64;
+            lot.cost_basis = lot
+                .cost_basis
+                .checked_add(cost)
+                .expect("fixed-point lot cost overflow");
             if self.quantity > 0 && self.average_cost.is_finite() && self.average_cost > 0.0 {
-                self.average_cost += cost / self.quantity as f64;
+                self.average_cost += cost.to_f64() / self.quantity as f64;
             } else {
                 self.recalculate_average_cost();
             }
         }
-        self.day_trade_cost += cost;
+        self.day_trade_cost = self
+            .day_trade_cost
+            .checked_add(cost)
+            .expect("fixed-point day trade cost overflow");
         self.refresh_day_pnl();
     }
 
     pub fn set_dividend_receivable(&mut self, value: f64) {
         self.dividend_receivable = if value.is_finite() {
-            value.max(0.0)
+            fixed_money_or_panic(value.max(0.0), "position dividend receivable")
         } else {
-            0.0
+            FixedMoney::ZERO
         };
     }
 
@@ -306,12 +435,7 @@ impl Position {
         if self.quantity == 0 {
             return None;
         }
-        let total = self
+        Some(self.total_entry_value().to_f64() / self.quantity as f64)
-            .lots
-            .iter()
-            .map(|lot| lot.entry_price * lot.quantity as f64)
-            .sum::<f64>();
-        Some(total / self.quantity as f64)
     }
 
     fn recalculate_average_cost(&mut self) {
@@ -320,13 +444,23 @@ impl Position {
             return;
         }
 
-        let total_cost = self
+        self.average_cost = self.total_cost_basis().to_f64() / self.quantity as f64;
-            .lots
+    }
-            .iter()
-            .map(|lot| lot.price * lot.quantity as f64)
-            .sum::<f64>();
 
-        self.average_cost = total_cost / self.quantity as f64;
+    fn total_entry_value(&self) -> FixedMoney {
+        self.lots.iter().fold(FixedMoney::ZERO, |total, lot| {
+            total
+                .checked_add(lot.entry_value)
+                .expect("fixed-point position entry value overflow")
+        })
+    }
+
+    fn total_cost_basis(&self) -> FixedMoney {
+        self.lots.iter().fold(FixedMoney::ZERO, |total, lot| {
+            total
+                .checked_add(lot.cost_basis)
+                .expect("fixed-point position cost basis overflow")
+        })
     }
 
     pub fn apply_cash_dividend(&mut self, dividend_per_share: f64) -> f64 {
@@ -346,20 +480,36 @@ impl Position {
             return 0.0;
         }
 
+        let mut cash_delta = FixedMoney::ZERO;
         for lot in &mut self.lots {
-            lot.entry_price -= dividend_per_share;
+            let lot_dividend = fixed_money_or_panic(
+                dividend_per_share * lot.quantity as f64,
+                "position cash dividend",
+            );
+            lot.entry_value = lot
+                .entry_value
+                .checked_sub(lot_dividend)
+                .expect("fixed-point lot entry dividend adjustment overflow");
             if adjust_cost_basis {
-                lot.price -= dividend_per_share;
+                lot.cost_basis = lot
+                    .cost_basis
+                    .checked_sub(lot_dividend)
+                    .expect("fixed-point lot cost dividend adjustment overflow");
             }
+            cash_delta = cash_delta
+                .checked_add(lot_dividend)
+                .expect("fixed-point cash dividend overflow");
         }
         if adjust_cost_basis {
             self.average_cost -= dividend_per_share;
         }
         self.last_price -= dividend_per_share;
-        let cash_delta = self.quantity as f64 * dividend_per_share;
+        self.day_dividend_cash = self
-        self.day_dividend_cash += cash_delta;
+            .day_dividend_cash
+            .checked_add(cash_delta)
+            .expect("fixed-point day dividend cash overflow");
         self.refresh_day_pnl();
-        cash_delta
+        cash_delta.to_f64()
     }
 
     pub fn apply_split_ratio(&mut self, ratio: f64) -> i32 {
@@ -374,8 +524,8 @@ impl Position {
             .map(|lot| PositionLot {
                 acquired_date: lot.acquired_date,
                 quantity: round_half_up_u32(lot.quantity as f64 * ratio),
-                entry_price: lot.entry_price / ratio,
+                entry_value: lot.entry_value,
-                price: lot.price / ratio,
+                cost_basis: lot.cost_basis,
             })
             .collect::<Vec<_>>();
 
@@ -410,13 +560,38 @@ impl Position {
         self.position_pnl = if self.day_start_quantity == 0 || self.day_start_price <= 0.0 {
             0.0
         } else {
+            fixed_money_or_panic(
                 adjusted_old_quantity
-                * (self.last_price - (self.day_start_price / self.day_split_ratio))
+                    * (self.last_price - (self.day_start_price / self.day_split_ratio)),
-                + self.day_dividend_cash
+                "position daily mark PnL",
+            )
+            .checked_add(self.day_dividend_cash)
+            .expect("fixed-point position daily PnL overflow")
+            .to_f64()
         };
-        self.trading_pnl = (self.day_buy_quantity as f64 * self.last_price - self.day_buy_value)
+        let buy_mark = if self.day_buy_quantity == 0 {
-            + (self.day_sell_value - self.day_sell_quantity as f64 * self.last_price)
+            FixedMoney::ZERO
-            - self.day_trade_cost;
+        } else {
+            fixed_money_or_panic(
+                self.day_buy_quantity as f64 * self.last_price,
+                "position day buy mark value",
+            )
+        };
+        let sell_mark = if self.day_sell_quantity == 0 {
+            FixedMoney::ZERO
+        } else {
+            fixed_money_or_panic(
+                self.day_sell_quantity as f64 * self.last_price,
+                "position day sell mark value",
+            )
+        };
+        self.trading_pnl = buy_mark
+            .checked_sub(self.day_buy_value)
+            .and_then(|value| value.checked_add(self.day_sell_value))
+            .and_then(|value| value.checked_sub(sell_mark))
+            .and_then(|value| value.checked_sub(self.day_trade_cost))
+            .expect("fixed-point position trading PnL overflow")
+            .to_f64();
     }
 }
 
@@ -467,7 +642,7 @@ pub(crate) struct SuccessorConversionOutcome {
 
 impl PortfolioState {
     pub fn new(initial_cash: f64) -> Self {
-        let initial_cash = Self::fixed_money(initial_cash, "initial cash")
+        let initial_cash = fixed_money(initial_cash, "initial cash")
             .expect("initial cash must be finite fixed-point money");
         Self {
             initial_cash,
@@ -539,7 +714,7 @@ impl PortfolioState {
     pub fn apply_cash_delta(&mut self, delta: f64) -> Result<(), String> {
         self.cash = self
             .cash
-            .checked_add(Self::fixed_money(delta, "cash delta")?)
+            .checked_add(fixed_money(delta, "cash delta")?)
             .ok_or_else(|| "fixed-point cash overflow".to_string())?;
         Ok(())
     }
@@ -565,9 +740,9 @@ impl PortfolioState {
     }
 
     pub fn deposit_withdraw(&mut self, amount: f64) -> Result<(), String> {
-        let amount_money = Self::fixed_money(amount, "deposit_withdraw amount")?;
+        let amount_money = fixed_money(amount, "deposit_withdraw amount")?;
         let pending_withdrawal =
-            Self::fixed_money(self.pending_withdrawal_total(), "pending withdrawal total")?;
+            fixed_money(self.pending_withdrawal_total(), "pending withdrawal total")?;
         let available_cash = self
             .cash
             .checked_sub(pending_withdrawal)
@@ -602,9 +777,9 @@ impl PortfolioState {
         amount: f64,
         reason: impl Into<String>,
     ) -> Result<(), String> {
-        let amount_money = Self::fixed_money(amount, "deposit_withdraw amount")?;
+        let amount_money = fixed_money(amount, "deposit_withdraw amount")?;
         let pending_withdrawal =
-            Self::fixed_money(self.pending_withdrawal_total(), "pending withdrawal total")?;
+            fixed_money(self.pending_withdrawal_total(), "pending withdrawal total")?;
         let available_cash = self
             .cash
             .checked_sub(pending_withdrawal)
@@ -685,7 +860,7 @@ impl PortfolioState {
         let mut settled = Vec::with_capacity(due.len());
         for flow in due {
             let unit_net_value = self.unit_net_value();
-            let amount = Self::fixed_money(flow.amount, "scheduled cash flow")?;
+            let amount = fixed_money(flow.amount, "scheduled cash flow")?;
             self.cash = self
                 .cash
                 .checked_add(amount)
@@ -714,7 +889,7 @@ impl PortfolioState {
     }
 
     pub fn finance_repay(&mut self, amount: f64) -> Result<(), String> {
-        let amount_money = Self::fixed_money(amount, "finance_repay amount")?;
+        let amount_money = fixed_money(amount, "finance_repay amount")?;
         if amount_money.raw() > 0 {
             self.cash_liabilities = self
                 .cash_liabilities
@@ -763,7 +938,7 @@ impl PortfolioState {
     }
 
     pub fn apply_management_fee(&mut self, fee: f64) -> Result<(), String> {
-        let fee_money = Self::fixed_money(fee, "management fee")?;
+        let fee_money = fixed_money(fee, "management fee")?;
         if fee_money.raw() < 0 {
             return Err("management fee must be finite and non-negative".to_string());
         }
@@ -969,11 +1144,11 @@ impl PortfolioState {
                         0.0
                     },
                     unrealized_pnl: position.unrealized_entry_pnl(),
-                    realized_pnl: position.realized_entry_pnl,
+                    realized_pnl: position.realized_entry_pnl(),
                     pnl: position.entry_pnl(),
                     trading_pnl: position.trading_pnl,
                     position_pnl: position.position_pnl,
-                    dividend_receivable: position.dividend_receivable,
+                    dividend_receivable: position.dividend_receivable(),
                     old_quantity: position.day_start_quantity(),
                     bought_quantity: position.bought_quantity(),
                     sold_quantity: position.sold_quantity(),
@@ -1015,8 +1190,8 @@ impl PortfolioState {
             .map(|lot| PositionLot {
                 acquired_date: lot.acquired_date,
                 quantity: round_half_up_u32(lot.quantity as f64 * ratio),
-                entry_price: lot.entry_price / ratio,
+                entry_value: lot.entry_value,
-                price: lot.price / ratio,
+                cost_basis: lot.cost_basis,
             })
             .collect::<Vec<_>>();
         let expected_total = round_half_up_u32(old_quantity as f64 * ratio);
@@ -1046,8 +1221,14 @@ impl PortfolioState {
         let successor_average_cost_before = successor.average_cost;
         successor.lots.extend(converted_lots);
         successor.quantity = successor.lots.iter().map(|lot| lot.quantity).sum();
-        successor.realized_pnl += realized_pnl;
+        successor.realized_pnl = successor
-        successor.realized_entry_pnl += realized_entry_pnl;
+            .realized_pnl
+            .checked_add(realized_pnl)
+            .expect("fixed-point successor realized PnL overflow");
+        successor.realized_entry_pnl = successor
+            .realized_entry_pnl
+            .checked_add(realized_entry_pnl)
+            .expect("fixed-point successor realized entry PnL overflow");
         if converted_last_price > 0.0 {
             successor.last_price = converted_last_price;
         }
@@ -1092,11 +1273,6 @@ impl PortfolioState {
         })
     }
 
-    fn fixed_money(value: f64, label: &str) -> Result<FixedMoney, String> {
-        FixedMoney::from_f64(value)
-            .ok_or_else(|| format!("{label} is not representable as fixed-point money: {value}"))
-    }
-
     fn sum_fixed_money(
         values: impl IntoIterator<Item = f64>,
         label: &str,
@@ -1105,7 +1281,7 @@ impl PortfolioState {
             .into_iter()
             .try_fold(FixedMoney::ZERO, |total, value| {
                 total
-                    .checked_add(Self::fixed_money(value, label)?)
+                    .checked_add(fixed_money(value, label)?)
                     .ok_or_else(|| format!("fixed-point {label} overflow"))
             })
     }
@@ -1125,8 +1301,8 @@ impl PortfolioState {
         unit_net_value_before: f64,
     ) -> Result<(), String> {
         if unit_net_value_before > 0.0 && unit_net_value_before.is_finite() {
-            let unit_nav = Self::fixed_money(unit_net_value_before, "unit net value")?;
+            let unit_nav = fixed_money(unit_net_value_before, "unit net value")?;
-            let total_equity = Self::fixed_money(self.total_equity(), "total equity")?;
+            let total_equity = fixed_money(self.total_equity(), "total equity")?;
             let units_raw = total_equity
                 .raw()
                 .checked_mul(MONEY_SCALE)
@@ -1164,6 +1340,48 @@ mod tests {
         assert_eq!(portfolio.cash(), 1_000_000.0);
     }
 
+    #[test]
+    fn fixed_lot_allocation_rounds_nearest_and_conserves_total() {
+        let total = FixedMoney::from_raw(5);
+        let allocated = allocate_fixed_value(total, 1, 2).expect("positive allocation");
+        let remainder = total.checked_sub(allocated).expect("positive remainder");
+        assert_eq!(allocated.raw(), 3);
+        assert_eq!(remainder.raw(), 2);
+        assert_eq!(allocated.checked_add(remainder), Some(total));
+
+        let negative_total = FixedMoney::from_raw(-5);
+        let negative_allocated =
+            allocate_fixed_value(negative_total, 1, 2).expect("negative allocation");
+        let negative_remainder = negative_total
+            .checked_sub(negative_allocated)
+            .expect("negative remainder");
+        assert_eq!(negative_allocated.raw(), -3);
+        assert_eq!(negative_remainder.raw(), -2);
+        assert_eq!(
+            negative_allocated.checked_add(negative_remainder),
+            Some(negative_total)
+        );
+    }
+
+    #[test]
+    fn fifo_fixed_pnl_conserves_value_while_alv_average_cost_stays_stable() {
+        let date = NaiveDate::from_ymd_opt(2025, 1, 2).unwrap();
+        let mut position = Position::new("000001.SZ");
+        position.buy(date, 100, 10.0);
+        position.record_buy_trade_cost(100, 5.0);
+        position.buy(date, 100, 5.0);
+        position.record_buy_trade_cost(100, 5.0);
+
+        let realized = position.sell(100, 6.0).expect("partial FIFO sell");
+
+        assert_eq!(position.quantity, 100);
+        assert!((position.average_cost - 7.55).abs() < 1e-12);
+        assert!((position.average_entry_price().unwrap() - 5.0).abs() < 1e-12);
+        assert!((realized + 405.0).abs() < 1e-12);
+        assert!((position.unrealized_pnl() - 95.0).abs() < 1e-12);
+        assert!((position.pnl() + 310.0).abs() < 1e-12);
+    }
+
     #[test]
     fn positions_preserve_insertion_order() {
         let date = NaiveDate::from_ymd_opt(2025, 1, 2).unwrap();
@@ -1471,7 +1689,7 @@ mod tests {
             .expect("close");
 
         let position = portfolio.position("000001.SZ").expect("position");
-        assert!((position.dividend_receivable - 25.0).abs() < 1e-6);
+        assert!((position.dividend_receivable() - 25.0).abs() < 1e-6);
         assert!((position.position_pnl - 70.0).abs() < 1e-6);
         assert!((position.trading_pnl + 5.0).abs() < 1e-6);
     }
@@ -1702,7 +1920,7 @@ mod tests {
         assert!((position.sell_avg_price() - 12.0).abs() < 1e-6);
         assert!((position.transaction_cost() - 3.0).abs() < 1e-6);
         assert!((realized - 80.0).abs() < 1e-6);
-        assert!((position.realized_pnl - 80.0).abs() < 1e-6);
+        assert!((position.realized_pnl() - 80.0).abs() < 1e-6);
         assert!((position.position_pnl - 200.0).abs() < 1e-6);
         assert!((position.trading_pnl - 47.0).abs() < 1e-6);
         assert!((position.pnl() - (80.0 + position.unrealized_pnl())).abs() < 1e-6);