Boolean / Logical Expression Shortcuts
The follow code snippets demo various approaches for achieving the same calculations/results using various boolean/logical expressions. Why would you want to ? Well, sometimes you can stumble upon alternative methods that might actually execute faster than the built in functionality. Which can be very useful if you're trying to squeeze out a bit more performance, or perhaps you're trying to write really unreadable code... :)
However, It's well worth keep in mind that just because Method A might be faster than method B today, it may not be in the future. So it always pays to query the performance of any approach you're using.
Related To
A Crash Course In Optimization (http://www.underwaredesign.com/forums/index.php?topic=2548.0)
Swapping Values
This was original written as query to the performance in DB eons ago. Interestingly, it's actually quicker than SWAP providing the operations are inline.
[pbcode]
type tTiming
Name$
StartTime
TotalTime
AverageTime#
Frames
endtype
Dim Times(100) as tTiming
// These flags are used for the display routines
Global ThisTest
Global DisplayLargest=true
// number of cycles to execute each test. We need a lot of tests in order to see any bias in the performance
MaxTests=5000
TestCounter=1000
// Values we're swapping
A =130
B =150
Do
Cls 0
print "Tests = "+str$(TestCounter)
print " A = "+str$(A);
print " B = "+str$(B);
ThisTest=0
StartTiming(ThisTest,"Swap Operation")
for lp=0 to MaxTests
swap A,B
next
DisplayResult(ThisTest)
StartTiming(ThisTest,"3 Move Swap")
for lp=0 to MaxTests
t=a
a=b
b=t
next
DisplayResult(ThisTest)
StartTiming(ThisTest,"4 Move Swap")
for lp=0 to MaxTests
t1=a
t2=b
a=t2
b=t1
next
DisplayResult(ThisTest)
StartTiming(ThisTest,"Xor Swap")
for lp=0 to MaxTests
maskab= (a xor b)
B=-1-((-1 xor a) xor maskab)
A=-1-((-1 xor b) XOR maskab)
next
DisplayResult(ThisTest)
StartTiming(ThisTest,"Mult/Div Swap")
for lp=0 to MaxTests
s=a*b
a=s/a
b=s/b
next
DisplayResult(ThisTest)
StartTiming(ThisTest,"Delta Swap")
for lp=0 to MaxTests
delta=(a-b)
a=a-delta
b=b+delta
next
DisplayResult(ThisTest)
Sync
decloop TestCounter
Print "Test Complete"
DisplayLargest=False
DisplayOrdersResults(ThisTest)
Sync
waitkey
Function DisplayResult(ThisTest)
s$=make$(" ",30)
message$= right$(s$+upper$(Times(ThisTest).Name$),30)
Message$=Message$+" Time:"+str$( EndTiming(ThisTest))
print Message$
inc ThisTest
EndFunction
Function StartTiming(Index,Message$)
Times(Index).Name$=Message$
Times(Index).StartTime=Timer()
Times(Index).Frames=Times(Index).Frames+1
EndFunction
Function EndTiming(Index)
Dt=Timer()-Times(Index).StartTime
Times(Index).TotalTime=Times(Index).TotalTime+Dt
Average#=float(Times(Index).TotalTime)/Times(Index).Frames
Times(Index).AverageTime=Average#
EndFunction Average#
Function DisplayOrdersResults(NumberOfItems)
Dim Mask(NumberOFItems)
Ink $ff00ff
print "RESULTS - Fastest to Slowest"
Ink $ff0000
for lp=0 to NumberOfItems-1
Lowest# =99999
LowestIndex =0
for SearchLp=0 to NumberOfItems-1
if Mask(Searchlp)=0
if Lowest#>Times(SearchLP).AverageTime
Lowest#=Times(SearchLP).AverageTime
LowestIndex=Searchlp
endif
endif
next
//
ThisTest=LowestINdex
Mask(LowestIndex)=true
DisplayResult(LowestIndex)
ink $ffffff
next
EndFunction
[/pbcode]
Highest Value
This is just some experiments with a few of detecting the highest of the two integer values.
[pbcode]
type tTiming
Name$
StartTime
TotalTime
AverageTime#
Frames
endtype
Dim Times(100) as tTiming
// These flags are used for the display routines
Global ThisTest
Global DisplayLargest=true
// number of cycles to execute each test. We need a lot of tests in order to see any bias in the performance
MaxTests=5000
TestCounter=1000
// Values we're comparing
A =130
B =150
Do
Cls 0
print "Tests = "+str$(TestCounter)
print " A = "+str$(A);
print " B = "+str$(B);
ThisTest=0
StartTiming(ThisTest,"IF / THEN")
for lp=0 to MaxTests
// use IF/THEN
C=A
if B>A then C=B
next
DisplayResult(ThisTest,C)
StartTiming(ThisTest,"IF / Else /ENDIF")
for lp=0 to MaxTests
// use IF/THEN
if B>A
B=B
else
C=A
endif
next
DisplayResult(ThisTest,C)
StartTiming(ThisTest,"MaxVal Function")
for lp=0 to MaxTests
c=maxval(a,b)
next
DisplayResult(ThisTest,C)
StartTiming(ThisTest,"Boolean With Mult")
for lp=0 to MaxTests
// Find the largest of two values
C= ((A>=B) * A) + ((A<B) * B)
next
DisplayResult(ThisTest,C)
StartTiming(ThisTest,"Boolean with bitwise and")
for lp=0 to MaxTests
// Find the largest of two values (without multiples)
C= ((-1+(A<=B)) & A) + ((-1+(A>B)) & B)
next
DisplayResult(ThisTest,C)
StartTiming(ThisTest,"Delta Method 1")
for lp=0 to MaxTests
// Delta method, find diff between values, then Add differnece if B larger then A.
C= A+((B-A)*(B>A))
next
DisplayResult(ThisTest,C)
StartTiming(ThisTest,"Delta Method 2")
for lp=0 to MaxTests
// No mult version of Delta method
C= A+(-1+(A>B) &(B-A))
next
DisplayResult(ThisTest,C)
Sync
decloop TestCounter
Print "Test Complete"
DisplayLargest=False
DisplayOrdersResults(ThisTest)
Sync
waitkey
Function DisplayResult(ThisTest,C)
s$=make$(" ",30)
message$= right$(s$+upper$(Times(ThisTest).Name$),30)
if DisplayLargest
Message$=Message$+" Largest Value:"+str$( c)
endif
Message$=Message$+" Time:"+str$( EndTiming(ThisTest))
print Message$
inc ThisTest
EndFunction
Function StartTiming(Index,Message$)
Times(Index).Name$=Message$
Times(Index).StartTime=Timer()
Times(Index).Frames=Times(Index).Frames+1
EndFunction
Function EndTiming(Index)
Dt=Timer()-Times(Index).StartTime
Times(Index).TotalTime=Times(Index).TotalTime+Dt
Average#=float(Times(Index).TotalTime)/Times(Index).Frames
Times(Index).AverageTime=Average#
EndFunction Average#
Function DisplayOrdersResults(NumberOfItems)
Dim Mask(NumberOFItems)
Ink $ff00ff
print "RESULTS - Fastest to Slowest"
Ink $ff0000
for lp=0 to NumberOfItems-1
Lowest# =99999
LowestIndex =0
for SearchLp=0 to NumberOfItems-1
if Mask(Searchlp)=0
if Lowest#>Times(SearchLP).AverageTime
Lowest#=Times(SearchLP).AverageTime
LowestIndex=Searchlp
endif
endif
next
//
ThisTest=LowestINdex
Mask(LowestIndex)=true
DisplayResult(LowestIndex,C)
ink $ffffff
next
EndFunction
[/pbcode]
Value Within Range
In this test, we're looking at some ways of detecting if a value falls within an inclusive (can be equal to the bottom and lower limits) range.
Note: we're assuming the range limited are in order here.
[pbcode]
type tTiming
Name$
StartTime
TotalTime
AverageTime#
Frames
endtype
Dim Times(100) as tTiming
// These flags are used for the display routines
Global ThisTest
Global DisplayLargest=true
// number of cycles to execute each test. We need a lot of tests in order to see any bias in the performance
MaxTests=5000
TestCounter=1000
// Ranges we're comparing within
RangeBottom=100
RangeTop=200
Value=150
Do
Cls 0
print "Tests = "+str$(TestCounter)
print " Range Bot = "+str$(RangeBottom);
print " Range Top = "+str$(RangeTop);
print " Test Value = "+str$(Value)
ThisTest=0
StartTiming(ThisTest,"Range Function")
for lp=0 to MaxTests
result=range(Value,RangeBottom,RangeTop)
next
DisplayResult(ThisTest)
print Result
StartTiming(ThisTest,"Combined Compare")
for lp=0 to MaxTests
// Combined Compare
Result=0
if (Value>=RangeBottom) and (Value<=RangeTop)
result=true
endif
next
DisplayResult(ThisTest)
print Result
StartTiming(ThisTest,"Split Compare")
for lp=0 to MaxTests
// Combined Compare
Result=0
if Value>=RangeBottom
if Value<=RangeTop
result=true
endif
endif
next
DisplayResult(ThisTest)
print Result
// Boolean Compare
StartTiming(ThisTest,"Boolean Compare (AND)")
for lp=0 to MaxTests
// Combined Compare
Result= (Value>=RangeBottom) and (Value<=RangeTop)
next
DisplayResult(ThisTest)
print Result
// Boolean Compare
StartTiming(ThisTest,"Boolean Compare (SUBTRACT)")
for lp=0 to MaxTests
// Combined Compare
Result= (Value>=RangeBottom) - (Value>RangeTop)
next
DisplayResult(ThisTest)
print Result
// Boolean Compare
StartTiming(ThisTest,"Split Boolean Compare")
for lp=0 to MaxTests
// Combined Compare
Result= (Value>=RangeBottom)
if Value>RangeTop
result=false
endif
next
DisplayResult(ThisTest)
print Result
Sync
decloop TestCounter
Print "Test Complete"
DisplayLargest=False
DisplayOrdersResults(ThisTest)
Sync
waitkey
Function DisplayResult(ThisTest)
s$=make$(" ",30)
message$= right$(s$+upper$(Times(ThisTest).Name$),30)
Message$=Message$+" Time:"+str$( EndTiming(ThisTest))
print Message$
inc ThisTest
EndFunction
Function StartTiming(Index,Message$)
Times(Index).Name$=Message$
Times(Index).StartTime=Timer()
Times(Index).Frames=Times(Index).Frames+1
EndFunction
Function EndTiming(Index)
Dt=Timer()-Times(Index).StartTime
Times(Index).TotalTime=Times(Index).TotalTime+Dt
Average#=float(Times(Index).TotalTime)/Times(Index).Frames
Times(Index).AverageTime=Average#
EndFunction Average#
Function DisplayOrdersResults(NumberOfItems)
Dim Mask(NumberOFItems)
Ink $ff00ff
print "RESULTS - Fastest to Slowest"
Ink $ff0000
for lp=0 to NumberOfItems-1
Lowest# =99999
LowestIndex =0
for SearchLp=0 to NumberOfItems-1
if Mask(Searchlp)=0
if Lowest#>Times(SearchLP).AverageTime
Lowest#=Times(SearchLP).AverageTime
LowestIndex=Searchlp
endif
endif
next
ThisTest=LowestINdex
Mask(LowestIndex)=true
DisplayResult(LowestIndex)
ink $ffffff
next
EndFunction
[/pbcode]
Distance/Range Checking
The follow examples run through various methods for detecting if an Target object is within a range of the Source object. You commonly find this type of calc in collisions. Interestingly the inline version is quickest in PB1.64j. Although you'd probably get the better results in a real world situation by screening the X or Y axis first, before falling into the distance calc. If objects are spread out, then this will act as early reject, otherwise we're calcing the distance every update.
[pbcode]
type tTiming
Name$
StartTime
TotalTime
AverageTime#
Frames
endtype
Dim Times(100) as tTiming
// These flags are used for the display routines
Global ThisTest
Global DisplayLargest=true
// number of cycles to execute each test. We need a lot of tests in order to see any bias in the performance
MaxTests=5000
TestCounter=500
// Ranges we're comparing within
ThisRange=400
RangeSquared=ThisRange*ThisRange
SrcObjectX=100
SrcObjectY=100
TargetX=200
TargetY=200
Do
Cls 0
print "Tests = "+str$(TestCounter)
ThisTest=0
StartTiming(ThisTest,"GetDistance Function")
for lp=0 to MaxTests
result=GetDistance2D(TargetX,TargetY,SrcObjectX,SrcObjectY)< ThisRange
next
DisplayResult(ThisTest)
print result
StartTiming(ThisTest,"Check Distance (SQRT) #1")
for lp=0 to MaxTests
result=CheckDistance(TargetX,TargetY,SrcObjectX,SrcObjectY,ThisRange)
next
DisplayResult(ThisTest)
print result
StartTiming(ThisTest,"Check Distance (SQRT) #2")
for lp=0 to MaxTests
result=CheckDistance2(TargetX,TargetY,SrcObjectX,SrcObjectY,ThisRange)
next
DisplayResult(ThisTest)
print result
StartTiming(ThisTest,"Check Distance (SQUARED) #3")
for lp=0 to MaxTests
result=CheckDistance3(TargetX,TargetY,SrcObjectX,SrcObjectY,ThisRange)
next
DisplayResult(ThisTest)
print result
StartTiming(ThisTest,"Check Distance (Pre SQUARED) #4")
for lp=0 to MaxTests
result=CheckDistance4(TargetX,TargetY,SrcObjectX,SrcObjectY,RangeSquared)
next
DisplayResult(ThisTest)
print result
StartTiming(ThisTest,"Inline (squared distance)")
for lp=0 to MaxTests
DiffX = SrcObjectX-TargetX
DiffY = SrcObjectY-TargetY
result=(DiffX*DiffX + DiffY*DiffY) < RangeSquared
next
DisplayResult(ThisTest)
print result
StartTiming(ThisTest,"Inline (squared distance & X axis compare)")
for lp=0 to MaxTests
if SrcObjectX<TargetX
DiffX=TargetX-SrcObjectX
else
DiffX=SrcObjectX-TargetX
endif
if DiffX<ThisRange
DiffY = SrcObjectY-TargetY
result=(DiffX*DiffX + DiffY*DiffY) < RangeSquared
else
result=0
endif
next
DisplayResult(ThisTest)
print result
StartTiming(ThisTest,"Inline (squared distance & X/Y axis compare)")
for lp=0 to MaxTests
result=0
if SrcObjectX<TargetX
DiffX=TargetX-SrcObjectX
else
DiffX=SrcObjectX-TargetX
endif
if DiffX<ThisRange
if SrcObjectY<TargetY
DiffY=TargetY-SrcObjectY
else
DiffY=SrcObjectY-TargetY
endif
if DiffY<ThisRange
result=(DiffX*DiffX + DiffY*DiffY) < RangeSquared
endif
endif
next
DisplayResult(ThisTest)
print result
Sync
decloop TestCounter
Print "Test Complete"
DisplayLargest=False
DisplayOrdersResults(ThisTest)
Sync
waitkey
Function DisplayResult(ThisTest)
s$=make$(" ",50)
message$= right$(s$+upper$(Times(ThisTest).Name$),50)
Message$=Message$+" Time:"+str$( EndTiming(ThisTest))
print Message$
inc ThisTest
EndFunction
Function StartTiming(Index,Message$)
Times(Index).Name$=Message$
Times(Index).StartTime=Timer()
Times(Index).Frames=Times(Index).Frames+1
EndFunction
Function EndTiming(Index)
Dt=Timer()-Times(Index).StartTime
Times(Index).TotalTime=Times(Index).TotalTime+Dt
Average#=float(Times(Index).TotalTime)/Times(Index).Frames
Times(Index).AverageTime=Average#
EndFunction Average#
Function DisplayOrdersResults(NumberOfItems)
Dim Mask(NumberOFItems)
Ink $ff00ff
print "RESULTS - Fastest to Slowest"
Ink $ff0000
for lp=0 to NumberOfItems-1
Lowest# =99999
LowestIndex =0
for SearchLp=0 to NumberOfItems-1
if Mask(Searchlp)=0
if Lowest#>Times(SearchLP).AverageTime
Lowest#=Times(SearchLP).AverageTime
LowestIndex=Searchlp
endif
endif
next
ThisTest=LowestINdex
Mask(LowestIndex)=true
DisplayResult(LowestIndex)
ink $ffffff
next
EndFunction
Psub CheckDistance(SrcObjectX,SrcObjectY,TargetX,TargetY,ThisRange)
DiffX = SrcObjectX-TargetX
DiffY = SrcObjectY-TargetY
Distance = sqrt(DiffX*DiffX + DiffY*DiffY)
if Distance < ThisRange
RetVal = 1
else
RetVal = 0
endif
EndPsub RetVal
Psub CheckDistance2(SrcObjectX,SrcObjectY,TargetX,TargetY,ThisRange)
DiffX = SrcObjectX-TargetX
DiffY = SrcObjectY-TargetY
RetVal= sqrt(DiffX*DiffX + DiffY*DiffY) < ThisRange
endPsub RetVal
Psub CheckDistance3(SrcObjectX,SrcObjectY,TargetX,TargetY,ThisRange)
DiffX = SrcObjectX-TargetX
DiffY = SrcObjectY-TargetY
RetVal=(DiffX*DiffX + DiffY*DiffY) < (ThisRange*ThisRange)
endPsub RetVal
Psub CheckDistance4(SrcObjectX,SrcObjectY,TargetX,TargetY,RangeSquared)
DiffX = SrcObjectX-TargetX
DiffY = SrcObjectY-TargetY
RetVal= (DiffX*DiffX + DiffY*DiffY) < RangeSquared
endPsub RetVal
[/pbcode]