Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Add fast Add, Multiply for numbers less than 2^64 #42

Merged
merged 2 commits into from
Jan 6, 2025
Merged

Add fast Add, Multiply for numbers less than 2^64 #42

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
a65a7ac
Add fast Add, Multiply for numbers less than 2^64
benaadams Jan 6, 2025
2a7da57
Add comment
benaadams Jan 6, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
67 changes: 53 additions & 14 deletions src/Nethermind.Int256/UInt256.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ namespace Nethermind.Int256

public UInt256(uint r0, uint r1, uint r2, uint r3, uint r4, uint r5, uint r6, uint r7)
{
if (Avx2.IsSupported)
if (Vector256<uint>.IsSupported)
{
Unsafe.SkipInit(out this.u0);
Unsafe.SkipInit(out this.u1);
Expand All @@ -52,7 +52,7 @@ public UInt256(uint r0, uint r1, uint r2, uint r3, uint r4, uint r5, uint r6, ui

public UInt256(ulong u0 = 0, ulong u1 = 0, ulong u2 = 0, ulong u3 = 0)
{
if (Avx2.IsSupported)
if (Vector256<ulong>.IsSupported)
{
Unsafe.SkipInit(out this.u0);
Unsafe.SkipInit(out this.u1);
Expand Down Expand Up @@ -82,7 +82,7 @@ public UInt256(in ReadOnlySpan<byte> bytes, bool isBigEndian = false)
}
else
{
if (Avx2.IsSupported)
if (Vector256<byte>.IsSupported)
{
Unsafe.SkipInit(out this.u0);
Unsafe.SkipInit(out this.u1);
Expand Down Expand Up @@ -187,7 +187,7 @@ public UInt256(in ReadOnlySpan<ulong> data, bool isBigEndian = false)
}
else
{
if (Avx2.IsSupported)
if (Vector256<ulong>.IsSupported)
{
Unsafe.SkipInit(out this.u0);
Unsafe.SkipInit(out this.u1);
Expand Down Expand Up @@ -404,6 +404,21 @@ public static void Add(in UInt256 a, in UInt256 b, out UInt256 res)

public static bool AddImpl(in UInt256 a, in UInt256 b, out UInt256 res)
{
if ((a.u1 | a.u2 | a.u3 | b.u1 | b.u2 | b.u3) == 0)
{
// Fast add for numbers less than 2^64 (18,446,744,073,709,551,615)
ulong u0 = a.u0 + b.u0;
// Assignment to res after in case is used as input for a or b (by ref aliasing)
res = default;
Unsafe.AsRef(in res.u0) = u0;
if (u0 < a.u0)
{
Unsafe.AsRef(in res.u1) = 1;
}
// Never overflows UInt256
return false;
}

if (Avx2.IsSupported)
{
Vector256<ulong> av = Unsafe.As<UInt256, Vector256<ulong>>(ref Unsafe.AsRef(in a));
Expand Down Expand Up @@ -982,6 +997,17 @@ private static void SubtractWithBorrow(ulong a, ulong b, ref ulong borrow, out u
// Multiply sets res to the product x*y
public static void Multiply(in UInt256 x, in UInt256 y, out UInt256 res)
{
if ((x.u1 | x.u2 | x.u3 | y.u1 | y.u2 | y.u3) == 0)
{
// Fast multiply for numbers less than 2^64 (18,446,744,073,709,551,615)
ulong high = Math.BigMul(x.u0, y.u0, out ulong low);
// Assignment to res after multiply in case is used as input for x or y (by ref aliasing)
res = default;
Unsafe.AsRef(in res.u0) = low;
Unsafe.AsRef(in res.u1) = high;
return;
}

ref ulong rx = ref Unsafe.As<UInt256, ulong>(ref Unsafe.AsRef(in x));
ref ulong ry = ref Unsafe.As<UInt256, ulong>(ref Unsafe.AsRef(in y));

Expand Down Expand Up @@ -1019,23 +1045,24 @@ public static bool MultiplyOverflow(in UInt256 x, in UInt256 y, out UInt256 res)
? 64 + Len64(u1)
: Len64(u0);

[SkipLocalsInit]
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private void Squared(out UInt256 result)
{
UInt256 z = this;
Span<ulong> res = stackalloc ulong[4];
(ulong carry0, ulong res0) = Multiply64(u0, u0);
(carry0, ulong temp1) = UmulHopi(carry0, u0, u1);
(carry0, ulong temp2) = UmulHopi(carry0, u0, u2);

(ulong carry0, res[0]) = Multiply64(z.u0, z.u0);
(carry0, ulong res1) = UmulHopi(carry0, z.u0, z.u1);
(carry0, ulong res2) = UmulHopi(carry0, z.u0, z.u2);
(ulong carry1, ulong res1) = UmulHopi(temp1, u0, u1);
(carry1, temp2) = UmulStepi(temp2,u1 , u1, carry1);

(ulong carry1, res[1]) = UmulHopi(res1, z.u0, z.u1);
(carry1, res2) = UmulStepi(res2, z.u1, z.u1, carry1);
(ulong carry2, ulong res2) = UmulHopi(temp2, u0, u2);

(ulong carry2, res[2]) = UmulHopi(res2, z.u0, z.u2);
// Don't care about carry here
ulong res3 = 2 * (u0 * u3 + u1 * u2) + carry0 + carry1 + carry2;

res[3] = 2 * (z.u0 * z.u3 + z.u1 * z.u2) + carry0 + carry1 + carry2;
result = new UInt256(res);
Unsafe.SkipInit(out result);
Unsafe.As<ulong, Vector256<ulong>>(ref Unsafe.AsRef(in result.u0)) = Vector256.Create(res0, res1, res2, res3);
}

public static void Exp(in UInt256 b, in UInt256 e, out UInt256 result)
Expand Down Expand Up @@ -1114,6 +1141,18 @@ public static void MultiplyMod(in UInt256 x, in UInt256 y, in UInt256 m, out UIn
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static void Umul(in UInt256 x, in UInt256 y, out UInt256 low, out UInt256 high)
{
if ((x.u1 | x.u2 | x.u3 | y.u1 | y.u2 | y.u3) == 0)
{
// Fast multiply for numbers less than 2^64 (18,446,744,073,709,551,615)
ulong highUL = Math.BigMul(x.u0, y.u0, out ulong lowUL);
// Assignment to high, low after multiply in case either is used as input for x or y (by ref aliasing)
high = default;
low = default;
Unsafe.AsRef(in low.u0) = lowUL;
Unsafe.AsRef(in low.u1) = highUL;
return;
}

(ulong carry, ulong l0) = Multiply64(x.u0, y.u0);
(carry, ulong res1) = UmulHopi(carry, x.u1, y.u0);
(carry, ulong res2) = UmulHopi(carry, x.u2, y.u0);
Expand Down
Loading