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

Improve performance of integer formatting #76726

Merged
merged 3 commits into from
Oct 11, 2022
Merged

Improve performance of integer formatting #76726

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
7a55dfd
Improve performance of integer formatting
stephentoub Oct 6, 2022
b69eaf4
Merge branch 'main' into fasterintegerformatting
stephentoub Oct 10, 2022
038fde7
Address PR feedback (move license notice)
stephentoub Oct 10, 2022
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
113 changes: 68 additions & 45 deletions ...libraries/System.Private.CoreLib/src/System/Buffers/Text/FormattingHelpers.CountDigits.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -52,60 +52,83 @@ public static int CountDigits(UInt128 value)
return digits;
}

// Based on do_count_digits from https://github.com/fmtlib/fmt/blob/662adf4f33346ba9aba8b072194e319869ede54a/include/fmt/format.h#L1124
/*
Formatting library for C++
Copyright (c) 2012 - present, Victor Zverovich
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
--- Optional exception to the license ---
As an exception, if, as a result of your compiling your source code, portions
of this Software are embedded into a machine-executable object form of such
source code, you may redistribute such embedded portions in such object form
without including the above copyright and permission notices.
*/
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static int CountDigits(ulong value)
{
int digits = 1;
uint part;
if (value >= 10000000)
// Map the log2(value) to a power of 10.
ReadOnlySpan<byte> log2ToPow10 = new byte[]
{
if (value >= 100000000000000)
{
part = (uint)(value / 100000000000000);
digits += 14;
}
else
{
part = (uint)(value / 10000000);
digits += 7;
}
}
else
{
part = (uint)value;
}
1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5,
6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 10,
10, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15,
15, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 19, 19, 19, 19, 20
};
Debug.Assert(log2ToPow10.Length == 64);
uint index = Unsafe.Add(ref MemoryMarshal.GetReference(log2ToPow10), BitOperations.Log2(value));

if (part < 10)
{
// no-op
}
else if (part < 100)
// TODO https://github.com/dotnet/runtime/issues/60948: Use ReadOnlySpan<ulong> instead of ReadOnlySpan<byte>.
// Read the associated power of 10.
ReadOnlySpan<byte> powersOf10 = new byte[]
{
digits++;
}
else if (part < 1000)
{
digits += 2;
}
else if (part < 10000)
{
digits += 3;
}
else if (part < 100000)
{
digits += 4;
}
else if (part < 1000000)
{
digits += 5;
}
else
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // unused entry to avoid needing to subtract
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 0
0x0A, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 10
0x64, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 100
0xE8, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 1000
0x10, 0x27, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 10000
0xA0, 0x86, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, // 100000
0x40, 0x42, 0x0F, 0x00, 0x00, 0x00, 0x00, 0x00, // 1000000
0x80, 0x96, 0x98, 0x00, 0x00, 0x00, 0x00, 0x00, // 10000000
0x00, 0xE1, 0xF5, 0x05, 0x00, 0x00, 0x00, 0x00, // 100000000
0x00, 0xCA, 0x9A, 0x3B, 0x00, 0x00, 0x00, 0x00, // 1000000000
0x00, 0xE4, 0x0B, 0x54, 0x02, 0x00, 0x00, 0x00, // 10000000000
0x00, 0xE8, 0x76, 0x48, 0x17, 0x00, 0x00, 0x00, // 100000000000
0x00, 0x10, 0xA5, 0xD4, 0xE8, 0x00, 0x00, 0x00, // 1000000000000
0x00, 0xA0, 0x72, 0x4E, 0x18, 0x09, 0x00, 0x00, // 10000000000000
0x00, 0x40, 0x7A, 0x10, 0xF3, 0x5A, 0x00, 0x00, // 100000000000000
0x00, 0x80, 0xC6, 0xA4, 0x7E, 0x8D, 0x03, 0x00, // 1000000000000000
0x00, 0x00, 0xC1, 0x6F, 0xF2, 0x86, 0x23, 0x00, // 10000000000000000
0x00, 0x00, 0x8A, 0x5D, 0x78, 0x45, 0x63, 0x01, // 100000000000000000
0x00, 0x00, 0x64, 0xA7, 0xB3, 0xB6, 0xE0, 0x0D, // 1000000000000000000
0x00, 0x00, 0xE8, 0x89, 0x04, 0x23, 0xC7, 0x8A, // 10000000000000000000
};
Debug.Assert((index + 1) * sizeof(ulong) <= powersOf10.Length);
ulong powerOf10 = Unsafe.ReadUnaligned<ulong>(ref Unsafe.Add(ref MemoryMarshal.GetReference(powersOf10), index * sizeof(ulong)));
if (!BitConverter.IsLittleEndian)
{
Debug.Assert(part < 10000000);
digits += 6;
powerOf10 = BinaryPrimitives.ReverseEndianness(powerOf10);
}

return digits;
// Return the number of digits based on the power of 10, shifted by 1
// if it falls below the threshold.
bool lessThan = value < powerOf10;
return (int)(index - Unsafe.As<bool, byte>(ref lessThan)); // while arbitrary bools may be non-0/1, comparison operators are expected to return 0/1
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
Expand Down
Loading