Split CPU and GPU exponent steppers

PerfectNumbers.Core/ThreadStaticPools.cs

@@ -329,31 +329,31 @@ namespace PerfectNumbers.Core
         }
 
         [ThreadStatic]
-        private static ExponentRemainderStepper _exponentRemainderStepper;
+        private static ExponentRemainderStepperCpu _exponentRemainderStepperCpu;
 
         [ThreadStatic]
-        private static bool _hasExponentRemainderStepper;
+        private static bool _hasExponentRemainderStepperCpu;
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal static ExponentRemainderStepper RentExponentStepper(in MontgomeryDivisorData divisorData)
+        internal static ExponentRemainderStepperCpu RentExponentStepperCpu(in MontgomeryDivisorData divisorData)
         {
-            if (_hasExponentRemainderStepper && _exponentRemainderStepper.MatchesDivisor(divisorData))
+            if (_hasExponentRemainderStepperCpu && _exponentRemainderStepperCpu.MatchesDivisor(divisorData))
             {
-                ExponentRemainderStepper stepper = _exponentRemainderStepper;
-                _hasExponentRemainderStepper = false;
+                ExponentRemainderStepperCpu stepper = _exponentRemainderStepperCpu;
+                _hasExponentRemainderStepperCpu = false;
                 stepper.Reset();
                 return stepper;
             }
 
-            return new ExponentRemainderStepper(divisorData);
+            return new ExponentRemainderStepperCpu(divisorData);
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal static void ReturnExponentStepper(ExponentRemainderStepper stepper)
+        internal static void ReturnExponentStepperCpu(ExponentRemainderStepperCpu stepper)
         {
             stepper.Reset();
-            _exponentRemainderStepper = stepper;
-            _hasExponentRemainderStepper = true;
+            _exponentRemainderStepperCpu = stepper;
+            _hasExponentRemainderStepperCpu = true;
         }
     }
 }