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Make by-divisor GPU kernels reuse read-only operands

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Marek Lemańczyk committed 2025-10-08 18:47:16 +02:00
1 parent cd1debe9d6
commit 6918bd28ff
8 files changed
+594 -250
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PerfectNumbers.Core/Gpu/GpuKernelPool.cs
+16 -11
View File
@@ -247,6 +247,7 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
GpuUInt128 q = twoP;
q.Mul64(k);
q.Add(GpuUInt128.One);
ReadOnlyGpuUInt128 readOnlyQ = q.AsReadOnly();
// Small-cycles in-kernel early rejection from device table
if (q.High == 0UL && q.Low < (ulong)smallCycles.Length)
@@ -271,13 +272,13 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
ulong phi64 = phi.Low;
// TODO: Replace these Pow2Mod calls with the ProcessEightBitWindows helper when the shared windowed
// scalar implementation lands; benchmarks showed the windowed kernel trimming per-divisor runtime by ~2.4×.
if (GpuUInt128.Pow2Mod(phi64, q) != GpuUInt128.One)
if (GpuUInt128.Pow2Mod(phi64, in readOnlyQ) != GpuUInt128.One)
{
orders[index] = 0UL;
return;
}
GpuUInt128 halfPow = GpuUInt128.Pow2Mod(phi64 >> 1, q) - GpuUInt128.One;
GpuUInt128 halfPow = GpuUInt128.Pow2Mod(phi64 >> 1, in readOnlyQ) - GpuUInt128.One;
if (GpuUInt128.BinaryGcd(halfPow, q) != GpuUInt128.One)
{
orders[index] = 0UL;
@@ -285,7 +286,7 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
}
ulong div = FastDiv64Gpu(phi64, exponent, divMul);
GpuUInt128 divPow = GpuUInt128.Pow2Mod(div, q) - GpuUInt128.One;
GpuUInt128 divPow = GpuUInt128.Pow2Mod(div, in readOnlyQ) - GpuUInt128.One;
if (GpuUInt128.BinaryGcd(divPow, q) != GpuUInt128.One)
{
orders[index] = 0UL;
@@ -298,6 +299,7 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
private static void OrderKernelScan(Index1D index, ulong exponent, ulong divMul, ArrayView<GpuUInt128> qs, ArrayView<ulong> orders)
{
GpuUInt128 q = qs[index];
ReadOnlyGpuUInt128 readOnlyQ = q.AsReadOnly();
GpuUInt128 phi = q - GpuUInt128.One;
if (phi.High != 0UL)
{
@@ -308,14 +310,14 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
ulong phi64 = phi.Low;
// TODO: Once the ProcessEightBitWindows helper is available, switch this order kernel to that faster
// Pow2Mod variant so cycle checks inherit the same gains observed in GpuPow2ModBenchmarks.
GpuUInt128 pow = GpuUInt128.Pow2Mod(phi64, q);
GpuUInt128 pow = GpuUInt128.Pow2Mod(phi64, in readOnlyQ);
if (pow != GpuUInt128.One)
{
orders[index] = 0UL;
return;
}
GpuUInt128 halfPow = GpuUInt128.Pow2Mod(phi64 >> 1, q) - GpuUInt128.One;
GpuUInt128 halfPow = GpuUInt128.Pow2Mod(phi64 >> 1, in readOnlyQ) - GpuUInt128.One;
if (GpuUInt128.BinaryGcd(halfPow, q) != GpuUInt128.One)
{
orders[index] = 0UL;
@@ -323,7 +325,7 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
}
ulong div = FastDiv64Gpu(phi64, exponent, divMul);
GpuUInt128 divPow = GpuUInt128.Pow2Mod(div, q) - GpuUInt128.One;
GpuUInt128 divPow = GpuUInt128.Pow2Mod(div, in readOnlyQ) - GpuUInt128.One;
if (GpuUInt128.BinaryGcd(divPow, q) != GpuUInt128.One)
{
orders[index] = 0UL;
@@ -410,6 +412,7 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
GpuUInt128 q = twoP;
q.Mul64(kStart);
q.Add(GpuUInt128.One);
ReadOnlyGpuUInt128 readOnlyQ = q.AsReadOnly();
if (q.High == 0UL && q.Low < (ulong)smallCycles.Length)
{
ulong cycle = smallCycles[(int)q.Low];
@@ -422,7 +425,7 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
}
// TODO: Swap Pow2Minus1Mod for the eight-bit window helper once the scalar version switches;
// benchmarks show the windowed variant cuts large-divisor scans from ~51 µs to ~21 µs.
if (GpuUInt128.Pow2Minus1Mod(exponent, q) != GpuUInt128.Zero)
if (GpuUInt128.Pow2Minus1Mod(exponent, in readOnlyQ) != GpuUInt128.Zero)
{
orders[index] = 0UL;
return;
@@ -559,6 +562,7 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
GpuUInt128 q = twoP;
q.Mul64(k);
q.Add(GpuUInt128.One);
ReadOnlyGpuUInt128 readOnlyQ = q.AsReadOnly();
// Small-cycles in-kernel early rejection from device table
if (q.High == 0UL && q.Low < (ulong)smallCycles.Length)
@@ -578,19 +582,19 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
ulong phi64 = phi.Low;
// TODO: Upgrade this pow2mod order kernel to the ProcessEightBitWindows helper once available so GPU residue
// scans avoid the single-bit ladder that benchmarks found to be 2.3× slower on large exponents.
if (GpuUInt128.Pow2Mod(phi64, q) != GpuUInt128.One)
if (GpuUInt128.Pow2Mod(phi64, in readOnlyQ) != GpuUInt128.One)
{
return;
}
GpuUInt128 halfPow = GpuUInt128.Pow2Mod(phi64 >> 1, q) - GpuUInt128.One;
GpuUInt128 halfPow = GpuUInt128.Pow2Mod(phi64 >> 1, in readOnlyQ) - GpuUInt128.One;
if (GpuUInt128.BinaryGcd(halfPow, q) != GpuUInt128.One)
{
return;
}
ulong div = FastDiv64Gpu(phi64, exponent, divMul);
GpuUInt128 divPow = GpuUInt128.Pow2Mod(div, q) - GpuUInt128.One;
GpuUInt128 divPow = GpuUInt128.Pow2Mod(div, in readOnlyQ) - GpuUInt128.One;
if (GpuUInt128.BinaryGcd(divPow, q) != GpuUInt128.One)
{
return;
@@ -645,6 +649,7 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
GpuUInt128 q = twoP;
q.Mul64(k);
q.Add(GpuUInt128.One);
ReadOnlyGpuUInt128 readOnlyQ = q.AsReadOnly();
// Small-cycles in-kernel early rejection from device table
if (q.High == 0UL && q.Low < (ulong)smallCycles.Length)
{
@@ -656,7 +661,7 @@ public ref struct GpuKernelLease(IDisposable limiter, GpuContextLease gpu, Kerne
}
// TODO: Replace this Pow2Mod check with the ProcessEightBitWindows helper once Pow2Minus1Mod adopts it;
// residue order scans will then benefit from the same 2× speedup the benchmarked windowed kernel delivered.
if (GpuUInt128.Pow2Mod(exponent, q) != GpuUInt128.One)
if (GpuUInt128.Pow2Mod(exponent, in readOnlyQ) != GpuUInt128.One)
{
return;
}