Add Decimal32, Decimal64, Decimal128 by RaymondHuy · Pull Request #100729 · dotnet/runtime

RaymondHuy · 2024-04-06T17:29:27Z

ghost · 2024-04-06T17:29:33Z

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

src/libraries/System.Private.CoreLib/src/System/Number.Parsing.cs

huoyaoyuan · 2024-04-07T15:27:03Z

src/libraries/System.Private.CoreLib/src/System/Numerics/Decimal128.cs

+        static int IDecimalIeee754UnpackInfo<Decimal128, Int128, UInt128>.NumberDigitsPrecision => NumberDigitsPrecision;
+
+
+        private static Int128[] Int128Powers10 =>


If Int128 is not optimized, this can be optimally stored as a ReadOnlySpan of Int32/Int64 like Number.BigInteger.Pow10BigNumTable

huoyaoyuan · 2024-04-07T15:28:42Z

src/libraries/System.Private.CoreLib/src/System/Numerics/Decimal128.cs

+        public override int GetHashCode()
+        {
+            return _value.GetHashCode();
+        }


+0 and -0 should have the same hash code. The easiest way can be stripping the sign bit.

I also remember that there can be same values with different representations.

runtime/src/libraries/System.Private.CoreLib/src/System/Numerics/TotalOrderIeee754Comparer.cs

Lines 125 to 132 in 9b57a26

else

{

// Equivalant values are compared by their exponent parts,

// and the value with smaller exponent is considered closer to zero.

// This only applies to IEEE 754 decimals. Consider to add support if decimals are added into .NET.

return 0;

}

@huoyaoyuan Thanks for your review. However this PR targets only the first phase as following: #81376 (comment) so I haven't added NegativeZero and PositiveZero. I will update GetHashCode method in the next phase.

src/libraries/System.Private.CoreLib/src/System/Numerics/Decimal128.cs

src/libraries/System.Private.CoreLib/src/System/Number.DecimalIeee754.cs

tannergooding · 2024-04-09T17:06:13Z

This is on my radar to take a look at; just noting it might be a bit delayed due to other priorities for the .NET 9 release.

CC. @jeffhandley

huoyaoyuan · 2025-11-19T01:56:46Z

src/libraries/System.Private.CoreLib/src/System/Numerics/Decimal128.cs

+        private static readonly UInt128 PositiveInfinityValue = new UInt128(upper: 0x7800_0000_0000_0000, lower: 0);
+        private static readonly UInt128 NegativeInfinityValue = new UInt128(upper: 0xf800_0000_0000_0000, lower: 0);
+        private static readonly UInt128 ZeroValue = new UInt128(0, 0);
+        private static readonly UInt128 NegativeZeroValue = new UInt128(0x8000_0000_0000_0000, 0);


Can this be a problem for codegen since UInt128 is not const?

They should probably be properties instead

Thanks, I have updated it.

huoyaoyuan · 2025-11-19T02:17:45Z

src/libraries/System.Private.CoreLib/src/System/Numerics/Decimal128.cs

+            return Number.FormatDecimalIeee754<Decimal128, UInt128>(this, format, NumberFormatInfo.GetInstance(provider));
+        }
+
+        private static UInt128[] UInt128Powers10 =>


This can be a problem for constant embedding. long array can be encoded into executable and read by pairs.

znakeeye · 2025-11-25T09:43:28Z

Are there any preliminary benchmarks of these new types? I.e. How do decimal128 and decimal64 compare to the existing decimal type?

Also, can we expect these new types to arrive in .NET 11?

huoyaoyuan · 2025-11-25T11:24:12Z

Are there any preliminary benchmarks of these new types? I.e. How do decimal128 and decimal64 compare to the existing decimal type?

We are focusing on the different semantic first. Both types are having different existing standard to follow.

Also, can we expect these new types to arrive in .NET 11?

It's optimistic, but not a guarantee.

RaymondHuy · 2025-12-10T02:21:08Z

Hi @tannergooding, thanks for your review, I have resolved almost your comments (handle NaN, TDecimal.MaxValue + (Delta / 2) vs TDecimal.MaxValue + ((Delta / 2) - 1) rounding, remove unsafe, update parameter names, added comments). Can you help me review it again ?

RaymondHuy · 2026-01-23T16:35:54Z

Hi @tannergooding can you help me take a look at this PR when you have time 😉

tannergooding · 2026-01-23T21:39:20Z

Yes, this is still on my backlog, just had some other work items that have been higher priority. Sorry for the delay

jeffhandley · 2026-02-16T02:04:16Z

@RaymondHuy Just reassuring you this is still on our radar. We are committed to getting this into .NET 11 as early in the release as we can.

Copilot

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 13 comments.

src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Decimal32Tests.cs

src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Decimal128Tests.cs

Copilot · 2026-02-16T02:12:05Z

src/libraries/System.Private.CoreLib/src/System/Numerics/Decimal128.cs

+        private static UInt128 NegativeZeroValue => new UInt128(0x8000_0000_0000_0000, 0);
+        private static UInt128 QuietNaNValue => new UInt128(0x7C00_0000_0000_0000, 0);
+        private static UInt128 MaxInternalValue = new UInt128(upper: 0x5FFF_ED09_BEAD_87C0, lower: 0x378D_8E63_FFFF_FFFF);
+        private static UInt128 MinInternalValue = new UInt128(upper: 0xDFFF_ED09B_EAD_87C0, lower: 0x378D_8E63_FFFF_FFFF);


There appears to be a typo in the hexadecimal constant. The value 0xDFFF_ED09B_EAD_87C0 contains an extra 'B' after '09'. It should likely be 0xDFFF_ED09_BEAD_87C0 to match the pattern in MaxInternalValue on line 39.

Suggested change

private static UInt128 MinInternalValue = new UInt128(upper: 0xDFFF_ED09B_EAD_87C0, lower: 0x378D_8E63_FFFF_FFFF);

private static UInt128 MinInternalValue = new UInt128(upper: 0xDFFF_ED09_BEAD_87C0, lower: 0x378D_8E63_FFFF_FFFF);

src/libraries/System.Private.CoreLib/src/System/Numerics/Decimal128.cs

src/libraries/System.Private.CoreLib/src/System/Numerics/Decimal32.cs

src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Decimal32Tests.cs

src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Decimal64Tests.cs

src/libraries/System.Runtime/tests/System.Runtime.Tests/System/Decimal128Tests.cs

src/libraries/System.Private.CoreLib/src/System/Numerics/Decimal64.cs

Copilot · 2026-02-16T02:12:08Z

src/libraries/System.Private.CoreLib/src/System/Number.BigInteger.cs

+                    return new UInt128(((ulong)(_blocks[3]) << 96) + ((ulong)_blocks[2] << 64), ((ulong)(_blocks[1]) << 32) + _blocks[0]);
+                }
+
+                if (_length > 2)
+                {
+                    return new UInt128(((ulong)_blocks[2] << 64), ((ulong)(_blocks[1]) << 32) + _blocks[0]);
+                }
+
+                if (_length > 1)
+                {
+                    return ((ulong)(_blocks[1]) << 32) + _blocks[0];


The bit shift operation ((ulong)(_blocks[3]) << 96) is incorrect. A ulong is 64 bits, so shifting it by 96 bits will produce 0 or undefined behavior. For a UInt128 with blocks stored as 32-bit values, the upper bits should be constructed differently. The correct approach should be: new UInt128(((ulong)_blocks[3] << 32) + _blocks[2], ((ulong)_blocks[1] << 32) + _blocks[0]) since UInt128 takes two ulong parameters (upper and lower 64 bits).

Suggested change

return new UInt128(((ulong)(_blocks[3]) << 96) + ((ulong)_blocks[2] << 64), ((ulong)(_blocks[1]) << 32) + _blocks[0]);

}

if (_length > 2)

{

return new UInt128(((ulong)_blocks[2] << 64), ((ulong)(_blocks[1]) << 32) + _blocks[0]);

}

if (_length > 1)

{

return ((ulong)(_blocks[1]) << 32) + _blocks[0];

return new UInt128(((ulong)_blocks[3] << 32) + _blocks[2], ((ulong)_blocks[1] << 32) + _blocks[0]);

}

if (_length > 2)

{

return new UInt128(_blocks[2], ((ulong)_blocks[1] << 32) + _blocks[0]);

}

if (_length > 1)

{

return ((ulong)_blocks[1] << 32) + _blocks[0];

jeffhandley · 2026-02-16T02:48:15Z

@RaymondHuy Copilot's review produced some good feedback comments. The using statements and unused variables look straightforward enough, but the bit-shifting comment warrants your analysis and consideration, so I've left all those comments unaddressed.

RaymondHuy · 2026-02-16T17:56:58Z

Hi @jeffhandley , thanks for your review, I have resolved all of them and also added test case to bit-shifting comment.

RaymondHuy added 5 commits March 11, 2024 13:08

add constructor info

ac5e447

Add Decimal32

1af3337

add test cases

cee05c8

Add Decimal128

da72dcd

add tests

6f3827c

ghost added area-System.Numerics new-api-needs-documentation labels Apr 6, 2024

RaymondHuy marked this pull request as draft April 6, 2024 17:29

dotnet-policy-service bot added the community-contribution Indicates that the PR has been added by a community member label Apr 6, 2024

RaymondHuy added 2 commits April 7, 2024 07:42

Merge commit '83b0d939bedadf7d782b0b26307c2d8c1d5b76f4' into issue-81376

7e9344b

Fix digits pointer

f882b96

RaymondHuy marked this pull request as ready for review April 7, 2024 01:22

RaymondHuy marked this pull request as draft April 7, 2024 01:23

This was referenced Apr 7, 2024

slow macOS - "##[error]The job running on agent Azure Pipelines 9 ran longer than the maximum time of 60 minutes." dotnet/dnceng#1883

Open

[browser][MT] TIMED_OUT but 0 was expected #99888

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huoyaoyuan reviewed Apr 7, 2024

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RaymondHuy added 2 commits April 9, 2024 23:22

Implement ToString() method.

762f56d

resolve comments

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resolve comments

83937d2

RaymondHuy marked this pull request as ready for review April 9, 2024 17:21

build-analysis bot mentioned this pull request Apr 9, 2024

[browser] Process terminated assert handling at icall.c:6162 #100249

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Refactor shift operators to mask

19755ba

build-analysis bot mentioned this pull request Apr 10, 2024

ComInterfaceGenerator.Unit.Tests failed on linux-x64 running interpreter #100683

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RaymondHuy added 2 commits April 10, 2024 18:05

Extract common mask to property.

ede6ca3

add more tests

b4e5d34

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System.Text.RegularExpressions.Tests on Mono_Minijit_Debug-Ubuntu #100715

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RaymondHuy added 2 commits April 11, 2024 13:21

add comments

504f042

Add overflow message.

31ffd5c

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Cannot find 'arm64-v8a' device dotnet/dnceng#2284

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RaymondHuy added 2 commits November 18, 2025 23:48

resolve some comments

b4c97a5

update

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RaymondHuy added 4 commits November 19, 2025 10:53

fix negative zero failed tests

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add comments to clarify method parameters

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replace readonly by property

bdf86f5

fix wrong decimal 64 mask

1921014

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Unable to pull image from mcr.microsoft.com #117164

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RaymondHuy added 5 commits November 26, 2025 21:35

handle NaN value

ee2acad

add test cases for NaN number

a9362e3

Handle Ulp value

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Add test case for max value rounding

3f7be57

update

cef4924

RaymondHuy requested a review from tannergooding December 10, 2025 02:21

jeffhandley added this to the 11.0.0 milestone Feb 16, 2026

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Merge branch 'main' into issue-81376

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"We stopped hearing from agent Azure Pipelines 32. Verify the agent machine is running and has a healthy network connection" dotnet/dnceng#1886

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resolve comments

a3c87da

		static int IDecimalIeee754UnpackInfo<Decimal128, Int128, UInt128>.NumberDigitsPrecision => NumberDigitsPrecision;


		private static Int128[] Int128Powers10 =>

	else
	{
	// Equivalant values are compared by their exponent parts,
	// and the value with smaller exponent is considered closer to zero.

	// This only applies to IEEE 754 decimals. Consider to add support if decimals are added into .NET.
	return 0;
	}

	private static UInt128 MinInternalValue = new UInt128(upper: 0xDFFF_ED09B_EAD_87C0, lower: 0x378D_8E63_FFFF_FFFF);
	private static UInt128 MinInternalValue = new UInt128(upper: 0xDFFF_ED09_BEAD_87C0, lower: 0x378D_8E63_FFFF_FFFF);

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