Reuse GPU context for nested partial factoring

PerfectNumbers.Core/Gpu/GpuKernelPool.cs

@@ -46,6 +46,7 @@ public sealed class KernelContainer
     public MemoryBuffer1D<int, Stride1D.Dense>? SmallPrimeFactorExponentSlots;
     public MemoryBuffer1D<int, Stride1D.Dense>? SmallPrimeFactorCountSlot;
     public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimeFactorRemainingSlot;
+    public MemoryBuffer1D<byte, Stride1D.Dense>? SmallPrimeFactorFullyFactoredSlot;
     public MemoryBuffer1D<uint, Stride1D.Dense>? SmallPrimesLastOne;
     public MemoryBuffer1D<ulong, Stride1D.Dense>? SmallPrimesPow2LastOne;
     public MemoryBuffer1D<uint, Stride1D.Dense>? SmallPrimesLastSeven;
@@ -107,17 +108,20 @@ public readonly struct SmallPrimeFactorScratch
     public readonly MemoryBuffer1D<int, Stride1D.Dense> ExponentSlots;
     public readonly MemoryBuffer1D<int, Stride1D.Dense> CountSlot;
     public readonly MemoryBuffer1D<ulong, Stride1D.Dense> RemainingSlot;
+    public readonly MemoryBuffer1D<byte, Stride1D.Dense> FullyFactoredSlot;
 
     public SmallPrimeFactorScratch(
         MemoryBuffer1D<ulong, Stride1D.Dense> primeSlots,
         MemoryBuffer1D<int, Stride1D.Dense> exponentSlots,
         MemoryBuffer1D<int, Stride1D.Dense> countSlot,
-        MemoryBuffer1D<ulong, Stride1D.Dense> remainingSlot)
+        MemoryBuffer1D<ulong, Stride1D.Dense> remainingSlot,
+        MemoryBuffer1D<byte, Stride1D.Dense> fullyFactoredSlot)
     {
         PrimeSlots = primeSlots;
         ExponentSlots = exponentSlots;
         CountSlot = countSlot;
         RemainingSlot = remainingSlot;
+        FullyFactoredSlot = fullyFactoredSlot;
     }
 
     public void Clear()
@@ -126,6 +130,7 @@ public readonly struct SmallPrimeFactorScratch
         ExponentSlots.MemSetToZero();
         CountSlot.MemSetToZero();
         RemainingSlot.MemSetToZero();
+        FullyFactoredSlot.MemSetToZero();
     }
 }
 
@@ -273,7 +278,14 @@ public class GpuKernelPool
                 kernels.SmallPrimeFactorRemainingSlot = remainingSlot;
             }
 
-            return new SmallPrimeFactorScratch(primeSlots!, exponentSlots!, countSlot!, remainingSlot!);
+            MemoryBuffer1D<byte, Stride1D.Dense>? fullyFactoredSlot = kernels.SmallPrimeFactorFullyFactoredSlot;
+            if (fullyFactoredSlot is null)
+            {
+                fullyFactoredSlot = accelerator.Allocate1D<byte>(1);
+                kernels.SmallPrimeFactorFullyFactoredSlot = fullyFactoredSlot;
+            }
+
+            return new SmallPrimeFactorScratch(primeSlots!, exponentSlots!, countSlot!, remainingSlot!, fullyFactoredSlot!);
         }
     }