Add Decimal32, Decimal64, Decimal128 #100729

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

tannergooding · 2025-11-14T17:36:24Z

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

+            }
+        }
+
+        private static unsafe TValue DecimalIeee754BinaryEncoding<TDecimal, TValue>(bool signed, TValue significand, int exponent)


nit: exponent and significand are swapped compared to the typical order of such APIs

These types of APIs, even though they are private/internal, likely also benefit from XML doc comments to be explicit that that significand is the "full" (non-trailing) significand and exponent is the unbiased exponent.

The terms get interchanged a lot and so being explicit can help ensure future readers understand the intent.

Thanks, I have updated the method name and added comments to help it readable.

tannergooding · 2025-11-14T17:39:16Z

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

+            byte[] buffer = ArrayPool<byte>.Shared.Rent(TDecimal.BufferLength);
+            try
+            {
+                fixed (byte* pDigits = buffer)


more cases that are using unnecessary unsafe. NumberBuffer takes a span

Thanks, I have updated it.

tannergooding · 2025-11-14T17:39:55Z

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

+                    char* stackPtr = stackalloc char[CharStackBufferSize];
+                    var vlb = new ValueListBuilder<char>(new Span<char>(stackPtr, CharStackBufferSize));


this can directly use stackalloc in the ValueListBuilder constructor as well, since the language will convert it to span implicitly

Hi @tannergooding , I follow your instruction, but it throws this error,

do you have another suggestion, or we just keep the old one.

Yeah, unfortunately there's actually a missing language feature here due to how we pass the data to NumberToString. We need ref scoped SomeRefStruct to do this one in particular.

Other callouts may not need that feature, just this one in particular does.

tannergooding · 2025-11-14T17:40:36Z

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

+            finally
+            {
+                ArrayPool<byte>.Shared.Return(buffer);
+            }


We don't typically put the return in a finally block. An exception being thrown is very unexpected and returning is not required for correctness

Thanks, I have removed the finally block.

tannergooding · 2025-11-14T17:41:02Z

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

+            where TValue : unmanaged, IBinaryInteger<TValue>
+        {
+            byte* buffer = number.DigitsPtr;
+            DecimalIeee754<TValue> unpackDecimal = value.Unpack();


Unpack should likely not be an extension method.

Hi @tannergooding , it is not an extension method, it is a method declared in IDecimalIeee754ParseAndFormatInfo interface

tannergooding · 2025-11-14T17:41:28Z

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

+            DecimalIeee754<TValue> unpackDecimal = value.Unpack();
+            number.IsNegative = unpackDecimal.Signed;
+
+            byte* p = buffer + TDecimal.Precision;


More cases that should use Span instead. There's a number of them and I don't plan to comment every instance

Thanks, I have updated it.

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 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

66a1127

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

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

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

Closed

RaymondHuy added 2 commits April 11, 2024 13:21

add comments

504f042

Add overflow message.

31ffd5c

tannergooding reviewed Nov 14, 2025

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RaymondHuy added 2 commits November 18, 2025 13:08

resolve some comments

e34d256

Merge branch 'master' into issue-81376

6947fe1

fix failed test cases

d17a6d3

build-analysis bot mentioned this pull request Nov 18, 2025

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

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3 tasks

RaymondHuy added 2 commits November 18, 2025 23:48

resolve some comments

b4c97a5

update

eb07b42

huoyaoyuan reviewed Nov 19, 2025

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RaymondHuy added 4 commits November 19, 2025 10:53

fix negative zero failed tests

5a1a8fe

add comments to clarify method parameters

516a200

replace readonly by property

bdf86f5

fix wrong decimal 64 mask

1921014

build-analysis bot mentioned this pull request Nov 19, 2025

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

Open

RaymondHuy added 5 commits November 26, 2025 21:35

handle NaN value

ee2acad

add test cases for NaN number

a9362e3

Handle Ulp value

8668878

Add test case for max value rounding

3f7be57

update

cef4924

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

		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;
	}

		char* stackPtr = stackalloc char[CharStackBufferSize];
		var vlb = new ValueListBuilder<char>(new Span<char>(stackPtr, CharStackBufferSize));

Add Decimal32, Decimal64, Decimal128 #100729

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Add Decimal32, Decimal64, Decimal128 #100729

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RaymondHuy commented Apr 6, 2024

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tannergooding commented Apr 9, 2024

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tannergooding Nov 18, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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znakeeye commented Nov 25, 2025

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huoyaoyuan commented Nov 25, 2025

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tannergooding Nov 18, 2025 •

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