Random numbers...

pizzaguy · 2009-02-06 17:45

Im trying to make a program to generate a random number between 1 and 10.

I figured I would start by doing this:

RANDOM startnum 
  number = startnum / 6553.5

if i understand RANDOM, then this should make a decimal between 1 and 10, but i need it to be rounded to whole numbers. How would i go about doing this?

ProcessingData... · 2009-02-06 18:03

Pizzaguy, try something like this:

startnum·VAR Nib

number·· VAR· Nib

DO

RANDOM startnum

LOOP UNTIL startnum < 11

number = startnum

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Basic Stamp,···· Propeller,·· · SX,·· FUN!

START:·
>Proccessing Data. . . .··
>Task Complete. . .·.
>Saving Data. . . .
>Entering SLEEP Mode. . . .
>Signing OFF

Post Edited (ProcessingData...) : 2/6/2009 6:11:19 PM GMT

Mike Green · 2009-02-06 18:18

Another good way to do this is

RANDOM startnum
result = (startnum // 10) + 1

pizzaguy · 2009-02-06 22:52

Thanks mike that worked great... but when I set up a script to show all of the numbers generated via DEBUG, the numbers are always the same. Is there a way around that?
I found the RANDOM example where it continuously generates a number to make a number that "appears" random. But im not quite sure how to integrate it into my program.

But basically my main question now is, is there a way to get the Time, or some sort of variable that will be based on the time, since time will never be the same making it a good seed for RANDOM?

Post Edited (pizzaguy) : 2/6/2009 11:06:47 PM GMT

Mike Green · 2009-02-06 23:03

1) I'd have to see the rest of your program to see why you're not getting random numbers. I can't tell from just your description.

2) I'd have to see the example you found. I can't guess what it is.

3) The Stamps do not have a built-in real time clock, so you can't get the time from somewhere in the chip. You can add an external real time clock chip like the DS1302 or DS1307 and there are examples of this in the Nuts and Volts Columns collection. If you had any reason to use an external keypad or some external pushbutton, you could use the time between button pushes as a "random" input.

pizzaguy · 2009-02-06 23:10

This is my basic code at the moment (its just a modification of some demo code for the Parallax SumoBot)

' -----[noparse][[/noparse] Title ]----------------------------------------------------------------
' Mini Sumo 3.3 : Simple Mini Sumo (blind)
' {$STAMP BS2}

' -----[noparse][[/noparse] I/O Definitions ]------------------------------------------------------

LMotor          CON     13                      ' left servo motor
RMotor          CON     12                      ' right servo motor


' -----[noparse][[/noparse] Constants ]------------------------------------------------------------

LFwdFast        CON     1000                    ' left motor forward; fast
LFwdSlow        CON      800                    ' left motor forward; slow
LStop           CON      750                    ' left motor stop

RFwdFast        CON      500                    ' right motor forward; fast
RFwdSlow        CON      700                    ' right motor forward; slow
RStop           CON      750                    ' right motor stop

ClrEOL          CON     11                      ' clear to end of line (DEBUG)

' -----[noparse][[/noparse] Variables ]------------------------------------------------------------

pulses          VAR     Byte                    ' counter for motor control
temp            VAR     Byte

' -----[noparse][[/noparse] EEPROM Data ]----------------------------------------------------------

RunStatus       DATA    $00                     ' run status

' -----[noparse][[/noparse] Initialization ]-------------------------------------------------------

Reset:                                      ' user Reset button as On-Off
  READ RunStatus, temp                          ' read current status
  temp = ~temp                                  ' invert status
  WRITE RunStatus, temp                         ' save status for next reset
  IF (temp > 0) THEN Start_Delay                ' run now?
  END

Start_Delay:                                    ' mandatory five second delay
  PAUSE 10

' -----[noparse][[/noparse] Main Code ]------------------------------------------------------------

Main:
Go_Fwd:
  PULSOUT LMotor, LFwdFast
  PULSOUT RMotor, RFwdFast
  GOTO Main

what i want to do is have the robot go strait for a random distance.

This is the RANDOM example: (according to the PBASIC reference "RANDOM is executed continuously (using the previous resulting number as the next seed value) while the program waits for the user to press a button.")

' RANDOM.BS2
' Connect a button to I/O pin 7 as shown in the figure in the RANDOM
' command description and run this program. This program uses RANDOM to
' simulate a coin toss. After 100 trials, it reports the total number of
' heads and tails thrown.

' {$STAMP BS2}
' {$PBASIC 2.5}

Btn             PIN     7                       ' button input

flip            VAR     Word                    ' a random number
coin            VAR     flip.BIT0               ' Bit0 of the random number
trials          VAR     Byte                    ' number of flips
heads           VAR     Byte                    ' throws that come up heads
tails           VAR     Byte                    ' throws that come up tails
btnWrk          VAR     Byte                    ' workspace for BUTTON


Start:
  DEBUG CLS, "Press button to start"

Main:
  FOR trials = 1 TO 100                         ' flip coin 100 times

Hold:
    RANDOM flip                                 ' randomize while waiting
    BUTTON Btin, 0, 250, 100, btnWrk, 0, Hold   ' wait for button press
    IF (coin = 0) THEN                          ' 0 = heads, 1 = tails
      DEBUG CR, "Heads!"
      heads = heads + 1                         ' increment heads counter
    ELSE
      DEBUG CR, "Tails..."
      tails = tails + 1                         ' increment tails counter
    ENDIF
  NEXT

Done:
  DEBUG CR, CR, "Heads: ", DEC heads, " Tails: ", DEC tails
  END

Mike Green · 2009-02-06 23:58

' -----[noparse][[/noparse] Variables ]------------------------------------------------------------

pulses          VAR     Byte                    ' counter for motor control
temp            VAR     Byte
temp2          VAR     Byte
ranVal          VAR     Word

' -----[noparse][[/noparse] EEPROM Data ]----------------------------------------------------------

RunStatus       DATA    $00                     ' run status
RanNum         DATA     $00,$00              ' random value (a word)

' -----[noparse][[/noparse] Initialization ]-------------------------------------------------------

Reset:                                      ' user Reset button as On-Off
  READ RunStatus, temp                          ' read current status
  temp = ~temp                                  ' invert status
  WRITE RunStatus, temp                         ' save status for next reset
  READ  RanNum, temp2
  READ RanNum+1,ranVal         ' Get random value
  ranVal = ranVal * 256 + temp2
  RANDOM ranVal
  WRITE RanNum,ranVal           ' Store updated random value
  WRITE RanNum+1,ranVal/256
  IF (temp > 0) THEN Start_Delay                ' run now?
  END

This will ensure that "ranVal" will have a new random value every time the Stamp is reset until the program is downloaded the next time which initializes the random value to zero. The robot will move every other time the Stamp is reset whether it's powered on or the reset button is pressed. The Stamp can't tell the difference between a reset from a power on or from a reset button push.

You can use "ranVal" any way you want to in the rest of the program.

Random numbers...

Comments