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I know vectorized code is faster than using loops, so I've been trying to so with this code. I was hoping someone could show me how to improve these for and if loops. The program is meant to calculate the power load curve of a house, taking into account whether the different appliances are switch on or switch off at different hours of day, month, and year.

The ProbFanSummerWd, ProbCellChargerSummerWd, etc. are probability matrices used to decide if the appliance is on or off based on a previous random "choose"; TotalLoad is the resultant power curve. This function is repeated many times within a larger program and consumes much time.

How could I improve those for and if loops? How can I replace them with vectorization?

I hope someone will help me. Thank you very much.

HourCount = 0; for DayYear = 1:size(Season,2) %LOOP - ONE YEAR if Season(DayYear) == 1 %LOOP - SUMMER SEASON if WeekDay(DayYear)>=1 && WeekDay(DayYear)<=5 %SUMMER WEEKDAY for Hour = 1:24 %LOOP - ONE DAY HourCount = HourCount+1; for h = 1:NumHouse %LOOP - HOUSE Choose = rand(1); %CellCharger if Choose <= ProbCellChargerSummerWd(Hour) TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ PowCellCharger; else TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ StandByCellCharger; end Choose = rand(1); %Fan if Choose <= ProbFanSummerWd(Hour) TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ PowFan; else TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ StandByFan; end Choose = rand(1); %Fridge if Choose <= ProbFridgeSummerWd(Hour) TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ PowFridge; else TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ StandByFridge; end Choose = rand(1); %Heater if Choose <= ProbHeaterSummerWd(Hour) TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ PowHeater; else TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ StandByHeater; end Choose = rand(1); %Iron if Choose <= ProbIronSummerWd(Hour) TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ PowIron; else TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ StandByIron; end Choose = rand(1); %LampKitchen if Choose <= ProbLampKitchenSummerWd(Hour) TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ PowLampKitchen; else TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ StandByLampKitchen; end Choose = rand(1); %LampRoom if Choose <= ProbLampRoomSummerWd(Hour) TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ PowLampRoom; else TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ StandByLampRoom; end Choose = rand(1); %Radio if Choose <= ProbRadioSummerWd(Hour) TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ PowRadio; else TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ StandByRadio; end Choose = rand(1); %TV20 if Choose <= ProbTvSummerWd(Hour) TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ PowTv; else TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ StandByTv; end end end
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It is helpful to work in small steps when vectorizing code. For example, in this code, you should start by trying only to vectorize only one if-statement in the innermost loop.

Take for example:

for h = 1:NumHouse %LOOP - HOUSE Choose = rand(1); %CellCharger if Choose <= ProbCellChargerSummerWd(Hour) TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ PowCellCharger; else TotalLoad(1,HourCount) = TotalLoad(1,HourCount)+ StandByCellCharger; end end

If you use the iterator in the code, I like to think about my goal is to replace all references to "h" (the iterator) with a ":" (vectorized version of the iterator).

If you do not use the iterator in the code, it is even easier. For example, the above code does not use the iterator, so we can simply rewrite the same in vectorized form, as:

Choose = rand(1, NumHouse); %CellCharger ChooseIdx = (Choose <= ProbCellChargerSummerWd(Hour)); TotalLoad(1,HourCount) = TotalLoad(1,HourCount) + ... ChooseIdx .* PowCellCharger + ... ~ChooseIdx .* StandByCellCharger;

That's it! No loops necessary!

Some other helpful vectorization tricks are available here. Once you have vectorized code, you can make it much faster using the GPU :)

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Thank you very much for your comments Mike Fineli, they have been very helpful to me!!!

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