Remove ineffective group lookup optimization from code review feedback

Code review correctly identified that caching group values in the while condition
doesn't reduce array accesses since the array is still accessed on every iteration.

Co-authored-by: Quafadas <24899792+Quafadas@users.noreply.github.com>

Author: Copilot

vecxtensions/src/Tower.scala

@@ -429,8 +429,7 @@ case class Tower( layers: Seq[Layer],  id: UUID = UUID.randomUUID(), name: Optio
         var cumSum = 0.0
 
         // Process block of same group, computing cumulative sum in-place
-        var groupValue = g
-        while i < numLosses && {groupValue = years(i); groupValue == g} do
+        while i < numLosses && years(i) == g do
           cumSum += cededRaw(columnOffset + i)
           cededRaw(columnOffset + i) = cumSum
           i += 1
@@ -523,8 +522,7 @@ case class Tower( layers: Seq[Layer],  id: UUID = UUID.randomUUID(), name: Optio
         var isFirstInGroup = true
 
         // Process block of same group, computing differences in-place
-        var groupValue = g
-        while i < numLosses && {groupValue = years(i); groupValue == g} do
+        while i < numLosses && years(i) == g do
           val currentValue = cededRaw(columnOffset + i)
           if isFirstInGroup then
             // First element in group gets its own value - no change needed

vecxtensions/src/groupCumSum.scala

@@ -19,9 +19,7 @@ inline def groupCumSum(groups: Array[Int], values: Array[Double]): Array[Double]
       var cumSum = 0.0
 
       // Process block of same group, computing cumulative sum
-      // Optimize by caching group lookup
-      var groupValue = g
-      while i < n && {groupValue = groups(i); groupValue == g} do
+      while i < n && groups(i) == g do
         cumSum += values(i)
         result(i) = cumSum
         i += 1
@@ -44,8 +42,7 @@ inline def groupCumSumInPlace(groups: Array[Int], values: Array[Double]): Unit =
       var cumSum = 0.0
 
       // Process block of same group, computing cumulative sum in-place
-      var groupValue = g
-      while i < n && {groupValue = groups(i); groupValue == g} do
+      while i < n && groups(i) == g do
         cumSum += values(i)
         values(i) = cumSum
         i += 1

vecxtensions/src/groupDiff.scala

@@ -21,9 +21,7 @@ inline def groupDiff(groups: Array[Int], values: Array[Double]): Array[Double] =
       var isFirstInGroup = true
 
       // Process block of same group, computing differences
-      // Optimize by caching group lookup
-      var groupValue = g
-      while i < n && {groupValue = groups(i); groupValue == g} do
+      while i < n && groups(i) == g do
         if isFirstInGroup then
           result(i) = values(i) // First element in group gets its own value
           isFirstInGroup = false
@@ -51,8 +49,7 @@ inline def groupDiffInPlace(groups: Array[Int], values: Array[Double]): Unit =
       var isFirstInGroup = true
 
       // Process block of same group, computing differences in-place
-      var groupValue = g
-      while i < n && {groupValue = groups(i); groupValue == g} do
+      while i < n && groups(i) == g do
         val currentValue = values(i)
         if isFirstInGroup then
           // First element in group gets its own value - no change needed