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Explore Stack InternalThisThis recent post reminded me that AbsoluteTime is a fast kernel function.
Using the RandomDates function from Leonid's post:
dates = RandomDates[500000]; Needs["Calendar`"] rls = Thread[ Range[0, 6] -> {Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday} ]; Timing[result1 = DayOfWeek /@ dates;] Timing[result2 = Mod[Quotient[AbsoluteTime /@ dates, 60^2 24], 7] /. rls;] result1 === result2 {37.783, Null} {0.921, Null} True
~ 41X speed-up.
This recent post reminded me that AbsoluteTime is a fast kernel function.
Using the RandomDates function from Leonid's post:
dates = RandomDates[500000]; Needs["Calendar`"] rls = Thread[ Range[0, 6] -> {Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday} ]; Timing[result1 = DayOfWeek /@ dates;] Timing[result2 = Mod[Quotient[AbsoluteTime /@ dates, 60^2 24], 7] /. rls;] result1 === result2 {37.783, Null} {0.921, Null} True
~ 41X speed-up.
This recent post reminded me that AbsoluteTime is a fast kernel function.
Using the RandomDates function from Leonid's post:
dates = RandomDates[500000]; Needs["Calendar`"] rls = Thread[ Range[0, 6] -> {Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday} ]; Timing[result1 = DayOfWeek /@ dates;] Timing[result2 = Mod[Quotient[AbsoluteTime /@ dates, 60^2 24], 7] /. rls;] result1 === result2 {37.783, Null} {0.921, Null} True
~ 41X speed-up.
This recent post reminded me that AbsoluteTime is a fast kernel function.
Using the RandomDates function from Leonid's post:
dates = RandomDates[500000]; Needs["Calendar`"] rls = Thread[ Range[0, 6] -> {Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday} ]; Timing[result1 = DayOfWeek /@ dates;] Timing[result2 = Mod[Quotient[AbsoluteTime /@ dates, 60^2 24], 7] /. rls;] result1 === result2 {37.783, Null} {0.921, Null} True
~ 41X speed-up.