Move core IoB loop from Decimal to Double

This commit converts one of the core internal IoB calculations from
using Decimal for numbers to Double. By using Double we give up on
precision but add speed due to hardware acceleration for floating
point math. The use of Double is confined to this internal algorithm,
the rest of the code that calls this function still operates on
Doubles.

Trio/Sources/APS/OpenAPSSwift/Iob/IobCalculation.swift

@@ -12,8 +12,8 @@ struct IobTotal: Codable {
 
 enum IobCalculation {
     struct IobCalculationResult {
-        let activityContrib: Decimal
-        let iobContrib: Decimal
+        let activityContrib: Double
+        let iobContrib: Double
     }
 
     /// logic to look up insulinPeakTime, taking into account `useCustomPeakTime`
@@ -65,7 +65,19 @@ enum IobCalculation {
         let iobContrib = insulin *
             (1 - S * (1 - a) * ((pow(minsAgo, 2) / (tau * end * (1 - a)) - minsAgo / tau - 1) * exp(-minsAgo / tau) + 1))
 
-        return IobCalculationResult(activityContrib: Decimal(activityContrib), iobContrib: Decimal(iobContrib))
+        guard activityContrib.isFinite, iobContrib.isFinite else {
+            return IobCalculationResult(activityContrib: 0, iobContrib: 0)
+        }
+
+        return IobCalculationResult(activityContrib: activityContrib, iobContrib: iobContrib)
+    }
+
+    /// Round a Double using the same logic as Decimal.jsRounded(scale:):
+    /// floor(value * 10^scale + 0.5) / 10^scale
+    private static func jsRound(_ value: Double, scale: Int) -> Decimal {
+        guard value.isFinite else { return 0 }
+        let multiplier = pow(10.0, Double(scale))
+        return Decimal((value * multiplier + 0.5).rounded(.down) / multiplier)
     }
 
     static func iobTotal(treatments: [ComputedPumpHistoryEvent], profile: Profile, time now: Date) throws -> IobTotal {
@@ -73,12 +85,12 @@ enum IobCalculation {
             throw IobError.diaNotSet
         }
 
-        var iob = Decimal(0)
-        var basaliob = Decimal(0)
-        var bolusiob = Decimal(0)
-        var netbasalinsulin = Decimal(0)
-        var bolusinsulin = Decimal(0)
-        var activity = Decimal(0)
+        var iob = 0.0
+        var basaliob = 0.0
+        var bolusiob = 0.0
+        var netbasalinsulin = 0.0
+        var bolusinsulin = 0.0
+        var activity = 0.0
 
         if dia < 5 {
             dia = 5
@@ -88,7 +100,7 @@ enum IobCalculation {
         let treatments = treatments.filter({ $0.timestamp <= now && $0.timestamp > diaAgo })
         for treatment in treatments {
             guard let tIOB = try iobCalc(treatment: treatment, time: now, dia: dia, profile: profile),
-                  let insulin = treatment.insulin
+                  let insulin = treatment.insulin.map({ Double($0) })
             else {
                 continue
             }
@@ -107,12 +119,12 @@ enum IobCalculation {
         }
 
         return IobTotal(
-            iob: iob.jsRounded(scale: 3),
-            activity: activity.jsRounded(scale: 4),
-            basaliob: basaliob.jsRounded(scale: 3),
-            bolusiob: bolusiob.jsRounded(scale: 3),
-            netbasalinsulin: netbasalinsulin.jsRounded(scale: 3),
-            bolusinsulin: bolusinsulin.jsRounded(scale: 3),
+            iob: jsRound(iob, scale: 3),
+            activity: jsRound(activity, scale: 4),
+            basaliob: jsRound(basaliob, scale: 3),
+            bolusiob: jsRound(bolusiob, scale: 3),
+            netbasalinsulin: jsRound(netbasalinsulin, scale: 3),
+            bolusinsulin: jsRound(bolusinsulin, scale: 3),
             time: now
         )
     }

TrioTests/OpenAPSSwiftTests/IobCalculateTests.swift

@@ -55,8 +55,8 @@ import Testing
         )
 
         #expect(result != nil)
-        #expect(result!.activityContrib.isWithin(0.0001, of: 0.0115))
-        #expect(result!.iobContrib.isWithin(0.0001, of: 1.8085))
+        #expect(result!.activityContrib.isApproximatelyEqual(to: 0.0115, epsilon: 0.0001))
+        #expect(result!.iobContrib.isApproximatelyEqual(to: 1.8085, epsilon: 0.0001))
     }
 
     @Test("should calculate IOB with custom peak time for rapid-acting insulin") func calculateCustomPeakRapidActing() async throws {
@@ -78,8 +78,8 @@ import Testing
         )
 
         #expect(result != nil)
-        #expect(result!.activityContrib.isWithin(0.0001, of: 0.0079))
-        #expect(result!.iobContrib.isWithin(0.0001, of: 1.8763))
+        #expect(result!.activityContrib.isApproximatelyEqual(to: 0.0079, epsilon: 0.0001))
+        #expect(result!.iobContrib.isApproximatelyEqual(to: 1.8763, epsilon: 0.0001))
     }
 
     @Test("should handle peak time limits for rapid-acting insulin") func handlePeakTimeLimitsRapidActing() async throws {
@@ -131,8 +131,8 @@ import Testing
         )
 
         #expect(result != nil)
-        #expect(result!.activityContrib.isWithin(0.0001, of: 0.01569))
-        #expect(result!.iobContrib.isWithin(0.0001, of: 1.7202))
+        #expect(result!.activityContrib.isApproximatelyEqual(to: 0.01569, epsilon: 0.0001))
+        #expect(result!.iobContrib.isApproximatelyEqual(to: 1.7202, epsilon: 0.0001))
     }
 
     @Test("should handle peak time limits for ultra-rapid insulin") func handlePeakTimeLimitsUltraRapid() async throws {