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snipsnip
Joined: 10 Feb 2014
Posts: 74
Location: Melbourne
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 Posted: Sun Mar 24, 2024 10:15 am Post subject: 2D array vs bootyfab |
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Hi guys, I've been working on this...
Is there any meaningful advantage to this method compared to using a standard 2d array in regards to execution speed?
it's for a 30 x 30 table
| Code: |
select case HeadingDeviation '/(case value = x axis)
case 1: Yaxis(0+accel) = balancepoint
case 2: Yaxis(30+accel) = balancepoint
case 3: Yaxis(60+accel) = balancepoint
case 4: Yaxis(90+accel) = balancepoint
case 5: Yaxis(120+accel) = balancepoint
case 6: Yaxis(150+accel) = balancepoint
case 7: Yaxis(180+accel) = balancepoint
case 8: Yaxis(210+accel) = balancepoint
case 9: Yaxis(240+accel) = balancepoint
case 10: Yaxis(270+accel) = balancepoint
case 11: Yaxis(300+accel) = balancepoint
case 12: Yaxis(330+accel) = balancepoint
case 13: Yaxis(360+accel) = balancepoint
case 14: Yaxis(390+accel) = balancepoint
case 15: Yaxis(420+accel) = balancepoint
case 16: Yaxis(450+accel) = balancepoint
case 17: Yaxis(480+accel) = balancepoint
case 18: Yaxis(510+accel) = balancepoint
case 19: Yaxis(540+accel) = balancepoint
case 20: Yaxis(570+accel) = balancepoint
case 21: Yaxis(600+accel) = balancepoint
case 22: Yaxis(630+accel) = balancepoint
case 23: Yaxis(660+accel) = balancepoint
case 24: Yaxis(690+accel) = balancepoint
case 25: Yaxis(720+accel) = balancepoint
case 26: Yaxis(750+accel) = balancepoint
case 27: Yaxis(780+accel) = balancepoint
case 28: Yaxis(810+accel) = balancepoint
case 29: Yaxis(840+accel) = balancepoint
case 30: Yaxis(870+accel) = balancepoint
end select |
(BASCOM-AVR version : 2.0.8.6 ) |
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albertsm
Joined: 09 Apr 2004
Posts: 5922
Location: Holland
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| Posted: Sun Mar 24, 2024 10:29 am Post subject: |
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i do not see the point of the select case, you can calculate the index right?
if you do not want to multiply you can also use a DATA table with the offset. then use lookup() get the index and add accel.
a huge select case with predictable values is not a good idea imo.
in worse case all values are checked before the proper is found. so that can take a long time.
you can easily test it with the sim.
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snipsnip
Joined: 10 Feb 2014
Posts: 74
Location: Melbourne
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| Posted: Sun Mar 24, 2024 11:11 am Post subject: |
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| albertsm wrote: | i do not see the point of the select case, you can calculate the index right?
if you do not want to multiply you can also use a DATA table with the offset. then use lookup() get the index and add accel.
a huge select case with predictable values is not a good idea imo.
in worse case all values are checked before the proper is found. so that can take a long time.
you can easily test it with the sim. |
Thanks for the reply.
I'd have thought select case would be the faster than a data table, but I assume a lot of incorrect stuff 
I wrote the above not realising bascom did multiple dimensional arrays. It's ugly code and if it's not significantly faster I'll change to a proper 2d array.
Sorry to say - Ive never used the sim.
this below is from the help files, and is what got me second guessing about going down the proper 2d road.
'While using multiple indexes might be a nice feature, it comes with a penalty : the processor need to calculate the address in memory based on the indexes. The more indexes you add, the more calculations/code is required.' |
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albertsm
Joined: 09 Apr 2004
Posts: 5922
Location: Holland
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| Posted: Sun Mar 24, 2024 11:27 am Post subject: |
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yes multi dim requires more code. for an array(a,b,c,d) all the indexes must be multiplied with the size and added to get the proper memory location.
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MWS
Joined: 22 Aug 2009
Posts: 2262
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| Posted: Sun Mar 24, 2024 6:17 pm Post subject: Re: 2D array vs bootyfab |
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| snipsnip wrote: | | Is there any meaningful advantage to this method compared to using a standard 2d array in regards to execution speed? |
Your unrolled code executes in the statistical mean slower than calculating the index in a one-dimensional array and both execute faster than a two-dimensional one.
| Code: | Dim HeadingDeviation As Byte
Dim accel As Byte
Dim balancepoint As Byte
Dim Yaxis(900) As Byte
Dim testpos As Byte
select case HeadingDeviation ' 21 to 163 cycles
case 1: Yaxis(0+accel) = balancepoint ' 21
' ...
case 15: Yaxis(420+accel) = balancepoint ' 91
' ...
case 30: Yaxis(870+accel) = balancepoint ' 163
end select
Dim idx As Word
idx = HeadingDeviation - 1 ' 81 cycles
idx = idx * 30
idx = idx + accel
Yaxis(idx) = balancepoint
Dim Yax(30, 30) As Byte
Yax(HeadingDeviation, accel) = balancepoint ' 232 cycles |
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