Multiple if then optimization

**duncan303** · - 2nd March 2008, 15:47

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** · - 2nd March 2008, 18:14

Originally Posted by duncan303

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** · - 2nd March 2008, 20:24

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

**duncan303** · - 3rd March 2008, 00:10

Originally Posted by tenaja

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** · - 3rd March 2008, 00:25

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

**Mugelpower** · - 3rd March 2008, 07:06

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....

**sayzer** · - 3rd March 2008, 08:12

Here it is
982 words

Code:

<font color="#008000">@__config _XT_OSC &amp; _WDT_ON &amp; _MCLRE_ON &amp; _LVP_OFF &amp; _CP_OFF

</font><font color="#000080"><b>INCLUDE </b></font><font color="#008000"><b>&quot;modedefs.bas&quot;
</b></font><font color="#000080"><b>DEFINE </b></font>OSC <font color="#FF0000"><b>4
</b></font>Uin        <font color="#000080"><b>VAR WORD
</b></font>B0         <font color="#000080"><b>VAR WORD </b><i>' Cnt is a word variable
</i></font>InputData  <font color="#000080"><b>VAR WORD </b><i>' variable to receive data into
</i></font>RepNo      <font color="#000080"><b>VAR BYTE

</b><i>' START OF MAIN PROGRAM
'
</i></font>CMCON = <font color="#FF0000"><b>7 </b></font><font color="#000080"><i>' RA0-RA3 are digital I/O
</i></font>TRISA = <font color="#FF0000"><b>0 </b></font><font color="#000080"><i>' PORT A is output
</i></font>TRISB = <font color="#FF0000"><b>1 </b></font><font color="#000080"><i>' RB0 is Input others output

</i></font>Main:

     <font color="#000080"><b>SERIN </b></font>PORTB.<font color="#FF0000"><b>0</b></font>,N2400,B0
     B0 = <font color="#FF0000"><b>100 </b></font>* B0
     Uin = B0 / <font color="#FF0000"><b>207
     </b></font><font color="#000080"><b>GOSUB </b></font>Bargraph
     <font color="#000080"><b>PAUSE </b></font><font color="#FF0000"><b>5

</b></font><font color="#000080"><b>GOTO </b></font>Main

Bargraph:

<font color="#000080"><b>LCDOUT </b></font><font color="#FF0000"><b>$fe</b></font>,<font color="#FF0000"><b>1      </b></font><font color="#000080"><i>'Valid for all cases.

</i><b>SELECT CASE </b></font>Uin
       
 <font color="#000080"><b>CASE IS </b></font>&lt; <font color="#FF0000"><b>10 
      </b></font><font color="#000080"><b>LCDOUT </b></font><font color="#008000"><b>&quot;TOO LOW&quot;
 </b></font><font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>10 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>15
      </b></font>RepNo = <font color="#FF0000"><b>1
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>15 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>19
      </b></font>RepNo = <font color="#FF0000"><b>2
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>19 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>24
      </b></font>RepNo = <font color="#FF0000"><b>3
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>24 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>29
      </b></font>RepNo = <font color="#FF0000"><b>4
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>29 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>34
      </b></font>RepNo = <font color="#FF0000"><b>5
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>34 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>43
      </b></font>RepNo = <font color="#FF0000"><b>6
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>43 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>53
      </b></font>RepNo = <font color="#FF0000"><b>7
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>53 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>62 
      </b></font>RepNo = <font color="#FF0000"><b>8
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>62 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>72
      </b></font>RepNo = <font color="#FF0000"><b>8
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD
      <font color="#000080"><b>GOSUB </b></font>LCD2
      RepNo = <font color="#FF0000"><b>1      
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD
 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>72 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>81
      </b></font>RepNo = <font color="#FF0000"><b>8
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD
      <font color="#000080"><b>GOSUB </b></font>LCD2
      RepNo = <font color="#FF0000"><b>2
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>81 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>86
      </b></font>RepNo = <font color="#FF0000"><b>8
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD
      <font color="#000080"><b>GOSUB </b></font>LCD2
      RepNo = <font color="#FF0000"><b>3
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>86 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>91
      </b></font>RepNo = <font color="#FF0000"><b>8
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD
      <font color="#000080"><b>GOSUB </b></font>LCD2
      RepNo = <font color="#FF0000"><b>4
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>91 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>96
      </b></font>RepNo = <font color="#FF0000"><b>8
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD
      <font color="#000080"><b>GOSUB </b></font>LCD2
      RepNo = <font color="#FF0000"><b>5
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>96 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>100
      </b></font>RepNo = <font color="#FF0000"><b>8
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD
      <font color="#000080"><b>GOSUB </b></font>LCD2
      RepNo = <font color="#FF0000"><b>6
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>100 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>105
      </b></font>RepNo = <font color="#FF0000"><b>8
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD
      <font color="#000080"><b>GOSUB </b></font>LCD2
      RepNo = <font color="#FF0000"><b>7
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE IS </b></font>&gt; <font color="#FF0000"><b>105 </b></font><font color="#000080"><b>AND IS </b></font>&lt;= <font color="#FF0000"><b>110
      </b></font>RepNo = <font color="#FF0000"><b>8
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD
      <font color="#000080"><b>GOSUB </b></font>LCD2
      RepNo = <font color="#FF0000"><b>8
      </b></font><font color="#000080"><b>GOSUB </b></font>RepLCD

 <font color="#000080"><b>CASE ELSE 
      LCDOUT </b></font><font color="#FF0000"><b>$FE</b></font>,<font color="#FF0000"><b>$C0</b></font>,<font color="#008000"><b>&quot;TOO RICH&quot;
</b></font><font color="#000080"><b>END SELECT

RETURN

</b></font>RepLCD:
    <font color="#000080"><b>WHILE </b></font>RepNo &gt; <font color="#FF0000"><b>0
          </b></font><font color="#000080"><b>LCDOUT </b></font><font color="#FF0000"><b>255
          </b></font>RepNo = RepNo - <font color="#FF0000"><b>1
    </b></font><font color="#000080"><b>WEND
   </b></font><font color="#000080"><b>RETURN

</b></font>LCD2:
    <font color="#000080"><b>LCDOUT </b></font><font color="#FF0000"><b>$FE</b></font>,<font color="#FF0000"><b>$C0
    </b></font><font color="#000080"><b>RETURN
    
</b></font>

Btw:
Select case produces 100 words more!
So, if you go with your IF..THENs, it will be approx. 882 words, but select case provides a clean look.

**Acetronics2** · - 3rd March 2008, 08:46

Another way

Code:

'************************************************* ****************
'* 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 *
'  569 Lines
'************************************************* ****************
'
' DEFINITIONS

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


DEFINE OSC 4

NbPatterns	var Byte
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

bargraph:

IF Uin < 10 THEN LCDOUT $FE,1,"TOO LOW" : GOTO Show

IF Uin > 110 THEN LCDOUT $FE,1,"TOO HIGH" : GOTO Show


LOOKDOWN2 Uin , < [ 11,16,20,25,30,35,44,54,63], NbPatterns 

LCDOUT $FE, 1, REP 255\ NbPatterns

IF Uin > 62 THEN

LOOKDOWN2 Uin , < [ 63,73,82,87,92,97,101,106,111], NbPatterns 

LCDOUT $FE, 1, REP 255\ 8

LCDOUT $FE, $C0, REP 255\ NbPatterns

ENDIF

Show:

Pause 5 
goto main


END ' End of program

569 Words ...

Alain

skimask · - 3rd March 2008, 19:31

Originally Posted by sayzer

CASE IS >19 AND IS <= 24

Does the AND in the CASE IS actually work?
I thought the CASE could only take one parameter to work on...

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