Multiple if then optimization

[Mugelpower]

Hi Gurus of Picland,

I´m building a Lambdatester that flattens somewhat out the hard jump in output voltage between lean and rich.

wrote a code that works. Fine, and fast enough because theres hardly need for speed.

Way of simple code for Picdummies like me .

But if an oldschool mechanic like me looks at it even he knows that theres plenty room for codesaving.
You Gurus fall down your chairs laughing and crying at the same time, I know.

'************************************************* ****************
'* Name : Analogbargraph1(16F628A).BAS *
'* Author : M.David *
'* Notice : Copyright (c) 2008 [select VIEW...EDITOR OPTIONS] *
'* : All Rights Reserved *
'* Date : 28.02.2008 *
'* Version : 1.0 *
'* Notes : needs 12F675 for Lambdatesting device and LCD 1X16 *
'* : input 0.1 - 1.1 Volts in GPIO.0 *
'* : needs ADCserout(12F675).bas *
'************************************************* ****************
'
' DEFINITIONS

@__config _XT_OSC & _WDT_ON & _MCLRE_ON & _LVP_OFF & _CP_OFF
Include "modedefs.bas"
CMCON=%00000111


DEFINE OSC 4
Uin var word
B0 VAR word ' Cnt is a word variable
inputData var word ' variable to receive data into


' START OF MAIN PROGRAM
'
CMCON = 7 ' RA0-RA3 are digital I/O
TRISA = 0 ' PORT A is output
TRISB = 1 ' RB0 is Input others output

main:

Serin PORTB.0,N2400,B0
B0 = 100 * B0
Uin = B0 / 207
gosub bargraph
Pause 5
goto main

bargraph:

if Uin < 10 then LCDOUT $FE,1,"TOO LOW"
if (Uin > 10) and (Uin <= 15 ) then
LCDOUT $FE,1,255
endif

if (Uin > 15) and (Uin <= 19 ) then
LCDOUT $FE,1,255,255
endif
if (Uin > 19) and (Uin <= 24 ) then
LCDOUT $FE,1,255,255,255
endif
if (Uin > 24) and (Uin <= 29 ) then
LCDOUT $FE,1,255,255,255,255
endif
if (Uin > 29) and (Uin <= 34 ) then
LCDOUT $FE,1,255,255,255,255,255
endif
if (Uin > 34) and (Uin <= 43 ) then
LCDOUT $FE,1,255,255,255,255,255,255
endif
if (Uin > 43) and (Uin <= 53 ) then
LCDOUT $FE,1,255,255,255,255,255,255,255
endif
if (Uin > 53) and (Uin <= 62 ) then
LCDOUT $FE,1,255,255,255,255,255,255,255,255
endif
if (Uin > 62) and (Uin <= 72 ) then
LCDOUT $FE,1,255,255,255,255,255,255,255,255,$FE,$C0,255
endif
if (Uin > 72) and (Uin <= 81 ) then
LCDOUT $FE,1,255,255,255,255,255,255,255,255,$FE,$C0,255, 255
endif
if (Uin > 81) and (Uin <= 86 ) then
LCDOUT $FE,1,255,255,255,255,255,255,255,255,$FE,$C0,255, 255,255
endif
if (Uin > 86) and (Uin <= 91 ) then
LCDOUT $FE,1,255,255,255,255,255,255,255,255,$FE,$C0,255, 255,255,255
endif
if (Uin > 91) and (Uin <= 96 ) then
LCDOUT $FE,1,255,255,255,255,255,255,255,255,$FE,$C0,255, 255,255,255,255
endif
if (Uin > 96) and (Uin <= 100 ) then
LCDOUT $FE,1,255,255,255,255,255,255,255,255,$FE,$C0,255, 255,255,255,255,255
endif
if (Uin > 100) and(Uin <= 105 ) then
LCDOUT $FE,1,255,255,255,255,255,255,255,255,$FE,$C0,255, 255,255,255,255,255,255
endif
if (Uin > 105) and(Uin <= 110 ) then
LCDOUT $FE,1,255,255,255,255,255,255,255,255,$FE,$C0,255, 255,255,255,255,255,255,255
endif
if Uin > 110 then
LCDOUT $FE,$C0,"TOO RICH"
endif

return

END ' End of program

on the other hand it works and shows how good and fast the combination of pics and PBP works.

Any Ideas? maybe case select or lookdown or whatever?

sincerely

Mugel

[Acetronics2]

Hi,

The Obvious Command is ... SELECT CASE

Note here you check Twice your values ... a better test arrangement looks like :

IF Value < 19
....
ENDIF

IF Value < 24
....
ENDIF

IF Value < 29
....
ENDIF

also can be used ...

IF Value < 10 THEN LCDOUT $FE, 1, "TOO LOW" 

LOOKDOWN2 Value , < ,[ 10,15,19,24,29, ....], NbPatterns 

LCDOUT $FE, 1, REP 255\ NbPatterns

Which is ... Somewhat shorter ( from the listing point of view ...)

Alain

[duncan303]

hi Mugel,

I don't know where all the gurus are today, but in thier absence I glanced at your post and thought you might like to take a look at the >select case< command. As all your conditions are sequentially discrete then this might be worth considering.

The trouble with long lists of if..thens are that once the condition is met (let say at the begginning of the list) then the program continues to chunder through all the remaining if...thens, whereas select case will exit at >end case< once the condition is met. Be careful though if your conditions are not discrete ,then you will have to arrange the cases in order of preference.

As to code space, I cannot remember but you could quickly swap the code over and see which is smaller.


Duncan

[tenaja]

The trouble with long lists of if..thens are that once the condition is met (let say at the beginning of the list) then the program continues to chunder through all the remaining if...thens, whereas select case will exit at >end case< once the condition is met. Be careful though if your conditions are not discrete ,then you will have to arrange the cases in order of preference.

Duncan

The way around this is to nest them, and put the largest value at the top. For instance, instead of this...

if a < 5 then...
endif...
if a < 10 then...
endif...

You do this for nesting:
if a < 10 then
if a < 5 then
code here...
else
code here...
endif
endif

or this for simple and fast testing:
if a < 10 then
code here...
goto SkipTests
endif
if a < 5
code here...
endif

SkipTests:

Using this method skips all of the IF's if the most extreme condition isn't true. All of this depends upon the assumption that the value of "a" isn't changed within any of the conditional statements.

[Archangel]

Hi Mugelpower,
Have you tried Darrel's Bargraph routine?
http://www.picbasic.co.uk/forum/showthread.php?t=2359

[duncan303]

The way around this is to nest them, and put the largest value at the top.

I am curious if this would compile with the list that Mugel has created, some 20 nested if…then...Else’s on a 16F device?

Duncan

[tenaja]

It should. I believe it just uses goto's, no stack use.

[Mugelpower]

yes the 20 if then work, no problem. Assembling took maybe 3 times longer then those blinky codes and it uses nearly 3/5 of the code space in my 16F628..but works flawlessly.

to Joe:

oh man I tried to use DTs bargraph routines but only got the error "coulnd´t open bargraph.bas" or something. Copied it in a "dozen" directories around the main PBP main and my project directories...didn´t work, always the same error.
But I uses DTs instant interrupt blinky program and that worked....so I don´t know a bone about how to work around "include" problems.

On the other my bargraph is quite crude with its big bars....but a fine bargraph isn´t an option here...way to hard to see while driving the car or bike, you need only sort of lean/rich tendencies and the lambda sensor it VERY jumpy around the stochiometric area.

8 leds would do but I did it mainly because of 3 reasons:

1.: I COULD do it.......with a little help of my friends....greetings to you all!
2.: One of my employees is sort of colour blind and wanted something to recocnize
without colours.
3.: we do a lot around sportscars engines and we test drive them mainly when the sun shines and a LED bargraph is hard to read while driving 100km/h in corners and the sun shining all over....

Yeah......I´m telling junk. Here in Germany the sun´s just a rumour you know, seen last time in june 2007 or so....