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Optimize DateTime.Year/.DayOfYear properties; fix comments #73277

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merged 16 commits into from
Aug 6, 2022
Merged

Optimize DateTime.Year/.DayOfYear properties; fix comments #73277

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77e8be2
Optimize DateTime.Year; fix comments
SergeiPavlov Aug 3, 2022
feb2931
Correct 'r1 = ...' comment
SergeiPavlov Aug 3, 2022
983a400
Optimize DateTime.DayOfYear
SergeiPavlov Aug 3, 2022
de9a57a
Shift instead of division
SergeiPavlov Aug 3, 2022
39a504a
Improve 'r1 = ' comments
SergeiPavlov Aug 3, 2022
6ef4798
Revert "Improve 'r1 = ' comments"
SergeiPavlov Aug 3, 2022
9057983
Further optimize DayOfYear
SergeiPavlov Aug 4, 2022
4dc340b
Change .Year implementation to uint arithmetic
SergeiPavlov Aug 4, 2022
e244a98
DayOfYear_RandomCheck() test
SergeiPavlov Aug 5, 2022
f7aae35
Use .Days instead of .TotalDays for simplicity
SergeiPavlov Aug 5, 2022
03f05c9
Add DayOfYear_Exhaustive
SergeiPavlov Aug 5, 2022
33a2574
Compare day by <=
SergeiPavlov Aug 5, 2022
00a4ce8
Speedup DayOfYear_Exhaustive test
SergeiPavlov Aug 5, 2022
085bdf3
fix unsed var varning
SergeiPavlov Aug 5, 2022
114c923
Remove Slow DayOfYear_Exhaustive test
SergeiPavlov Aug 5, 2022
8da61ac
Merge remote-tracking branch 'upstream/main' into optimize_DateTime_Year
SergeiPavlov Aug 6, 2022
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64 changes: 27 additions & 37 deletions src/libraries/System.Private.CoreLib/src/System/DateTime.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -104,9 +104,16 @@ public readonly partial struct DateTime
// All OA dates must be less than (not <=) OADateMaxAsDouble
private const double OADateMaxAsDouble = 2958466.0;

// Euclidean Affine Functions Algorithm constants
// Euclidean Affine Functions Algorithm (EAF) constants

// Constants used for fast calculation of following subexpressions
// x / DaysPer4Years
// x % DaysPer4Years / 4
private const uint EafMultiplier = (uint)(((1UL << 32) + DaysPer4Years - 1) / DaysPer4Years); // 2,939,745
private const uint EafDivider = EafMultiplier * 4; // 11,758,980

private const ulong TicksPer6Hours = TicksPerHour * 6;
private const int March1BasedDayOfNewYear = 306; // Days between March 1 and January 1
private const int March1BasedDayOfNewYear = 306; // Days between March 1 and January 1

private static readonly uint[] s_daysToMonth365 = {
0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
Expand Down Expand Up @@ -1356,13 +1363,13 @@ public DateTime Date
// Cassio Neri, Lorenz Schneiderhttps - Euclidean Affine Functions and Applications to Calendar Algorithms - 2021
internal void GetDate(out int year, out int month, out int day)
{
// y400 = number of whole 400-year periods since 3/1/0000
// r1 = day number within 400-year period
(uint y400, uint r1) = Math.DivRem(((uint)(UTicks / TicksPer6Hours) | 3U) + 1224, DaysPer400Years);
ulong u2 = (ulong)Math.BigMul(2939745, (int)r1 | 3);
ushort daySinceMarch1 = (ushort)((uint)u2 / 11758980);
// y100 = number of whole 100-year periods since 3/1/0000
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// r1 = (day number within 100-year period) * 4
(uint y100, uint r1) = Math.DivRem(((uint)(UTicks / TicksPer6Hours) | 3U) + 1224, DaysPer400Years);
ulong u2 = (ulong)Math.BigMul((int)EafMultiplier, (int)r1 | 3);
ushort daySinceMarch1 = (ushort)((uint)u2 / EafDivider);
int n3 = 2141 * daySinceMarch1 + 197913;
year = (int)(100 * y400 + (uint)(u2 >> 32));
year = (int)(100 * y100 + (uint)(u2 >> 32));
// compute month and day
month = (ushort)(n3 >> 16);
day = (ushort)n3 / 2141 + 1;
Expand Down Expand Up @@ -1419,10 +1426,10 @@ public int Day
{
get
{
// r1 = day number within 400-year period
// r1 = (day number within 100-year period) * 4
uint r1 = (((uint)(UTicks / TicksPer6Hours) | 3U) + 1224) % DaysPer400Years;
ulong u2 = (ulong)Math.BigMul(2939745, (int)r1 | 3);
ushort daySinceMarch1 = (ushort)((uint)u2 / 11758980);
ulong u2 = (ulong)Math.BigMul((int)EafMultiplier, (int)r1 | 3);
ushort daySinceMarch1 = (ushort)((uint)u2 / EafDivider);
int n3 = 2141 * daySinceMarch1 + 197913;
// Return 1-based day-of-month
return (ushort)n3 / 2141 + 1;
Expand All @@ -1439,22 +1446,8 @@ public int Day
// Returns the day-of-year part of this DateTime. The returned value
// is an integer between 1 and 366.
//
public int DayOfYear
{
get
{
// y400 = number of whole 400-year periods since 3/1/0000
// r1 = day number within 400-year period
(uint y400, uint r1) = Math.DivRem(((uint)(UTicks / TicksPer6Hours) | 3U) + 1224, DaysPer400Years);
ulong u2 = (ulong)Math.BigMul(2939745, (int)r1 | 3);
ushort daySinceMarch1 = (ushort)((uint)u2 / 11758980);

int year = (int)(100 * y400 + (uint)(u2 >> 32)) + (daySinceMarch1 >= March1BasedDayOfNewYear ? 1 : 0);
return daySinceMarch1 >= March1BasedDayOfNewYear // DatePartDayOfYear case
? daySinceMarch1 - March1BasedDayOfNewYear + 1 // rollover December 31
: daySinceMarch1 + (366 - March1BasedDayOfNewYear) + (IsLeapYear(year) ? 1 : 0);
}
}
public int DayOfYear =>
1 + (int)(((((uint)(UTicks / TicksPer6Hours) | 3U) % (uint)DaysPer400Years) | 3U) * EafMultiplier / EafDivider);

// Returns the hash code for this DateTime.
//
Expand Down Expand Up @@ -1510,10 +1503,10 @@ public int Month
{
get
{
// r1 = day number within 400-year period
// r1 = (day number within 100-year period) * 4
uint r1 = (((uint)(UTicks / TicksPer6Hours) | 3U) + 1224) % DaysPer400Years;
ulong u2 = (ulong)Math.BigMul(2939745, (int)r1 | 3);
ushort daySinceMarch1 = (ushort)((uint)u2 / 11758980);
ulong u2 = (ulong)Math.BigMul((int)EafMultiplier, (int)r1 | 3);
ushort daySinceMarch1 = (ushort)((uint)u2 / EafDivider);
int n3 = 2141 * daySinceMarch1 + 197913;
return (ushort)(n3 >> 16) - (daySinceMarch1 >= March1BasedDayOfNewYear ? 12 : 0);
}
Expand Down Expand Up @@ -1569,13 +1562,10 @@ public int Year
{
get
{
// y400 = number of whole 400-year periods since 3/1/0000
// r1 = day number within 400-year period
(uint y400, uint r1) = Math.DivRem(((uint)(UTicks / TicksPer6Hours) | 3U) + 1224, DaysPer400Years);
ulong u2 = (ulong)Math.BigMul(2939745, (int)r1 | 3);
ushort daySinceMarch1 = (ushort)((uint)u2 / 11758980);

return (int)(100 * y400 + (uint)(u2 >> 32)) + (daySinceMarch1 >= March1BasedDayOfNewYear ? 1 : 0);
// y100 = number of whole 100-year periods since 1/1/0001
// r1 = (day number within 100-year period) * 4
(uint y100, uint r1) = Math.DivRem(((uint)(UTicks / TicksPer6Hours) | 3U), DaysPer400Years);
return 1 + (int)(100 * y100 + (r1 | 3) / DaysPer4Years);
}
}

Expand Down
38 changes: 38 additions & 0 deletions src/libraries/System.Runtime/tests/System/DateTimeTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -811,6 +811,44 @@ public void DayOfYear_Get_ReturnsExpected()
Assert.Equal(170, dateTime.DayOfYear);
}

[Fact]
public void DayOfYear_Random()
{
var random = new Random(2022);
var tries = 1000;
for (int i = 0; i < tries; ++i)
{
var dateTime = new DateTime(random.NextInt64(DateTime.MaxValue.Ticks));
var startOfYear = new DateTime(dateTime.Year, 1, 1);
var expectedDayOfYear = 1 + (dateTime - startOfYear).Days;
Assert.Equal(expectedDayOfYear, dateTime.DayOfYear);
}
}

[Fact]
public void DayOfYear_Exhaustive()
{
var ticksPer6hours = TimeSpan.TicksPerHour * 6;
for (int year = DateTime.MinValue.Year, lastYear = DateTime.MaxValue.Year; year <= lastYear; ++year)
{
var startOfYear = new DateTime(year, 1, 1);
for (int expectedDayOfYear = 1, lastDayOfYear = DateTime.IsLeapYear(expectedDayOfYear) ? 366 : 365; expectedDayOfYear <= lastDayOfYear; ++expectedDayOfYear)
{
var dateTime = startOfYear.AddDays(expectedDayOfYear - 1); // .DayOfYear implementation uses 6-hour granularity value
Assert.Equal(expectedDayOfYear, dateTime.DayOfYear); // and we check 4 time points per day

dateTime = dateTime.AddTicks(ticksPer6hours);
Assert.Equal(expectedDayOfYear, dateTime.DayOfYear);

dateTime = dateTime.AddTicks(ticksPer6hours);
Assert.Equal(expectedDayOfYear, dateTime.DayOfYear);

dateTime = dateTime.AddTicks(ticksPer6hours);
Assert.Equal(expectedDayOfYear, dateTime.DayOfYear);
}
}
}

[Fact]
public void TimeOfDay_Get_ReturnsExpected()
{
Expand Down