division question

[golfnut]

Not great on this, hence the post..


Ive a factor to be held permanently in code and its 1333333.33

this forms the numerator every time I do a division conversion on a counter result.
A valid conversion may be :-

1333333.33 / 4092 hopefully would give 325.8 -I would like to display 326 on a 7segment!!
or
1333333.33 / 1332 or 1333 whatever,,,

24 bits for a numerator ??? also I dont like the look of the .33 on the end what would happen there??

GN

 

[eclectic]

1333333.33

That's a LOT of digits!
And a LOT of accuracy.

Is it anything to do with this thread?
http://www.picaxeforum.co.uk/showthread.php?t=14158&page=3

Or something else?

e

 

[golfnut]

Hi, no its this years project!

1333333.33 (dec) divided by nos in range 1330 to 4100 (dec)

I thought computers were good at math ??

 

[hippy]

A rewrite of code earlier today for 32-bit divided by 16-bit ...

#Picaxe 20X2
#No_Table
#No_data
#Terminal 9600

Symbol K       = 13333333
Symbol Kmsw    = K / $00010000
Symbol Klsw    = K & $0000FFFF

Symbol Ndiv    = w10
Symbol Nmsw    = w11
Symbol Nlsw    = w12
Symbol Nresult = w13

For Ndiv = 1330 To 4100

  SetFreq M64

  Nresult = 0
  Nmsw    = Kmsw
  Nlsw    = Klsw

  Do while Nmsw <> 0 Or Nlsw >= Ndiv
    If Nlsw < Ndiv Then
      Nmsw = Nmsw - 1
    End If
    Nlsw = Nlsw - Ndiv
    Nresult = Nresult + 1
  Loop

  BinToAscii Nresult, b1,b2,b3,b4,b5

  SetFreq M8

  SerTxd( "1333333.33 / ", #Ndiv, " ~= ", b1,b2,b3,b4,".",b5, CR, LF )

Next

 

[Jeremy Leach]

Hmmm, I think the fact that 4000000/3 = 1333333.33 has got to be a little significant here

I'd work with 4000000 and see if you can think of a way to simplify the division.

 

[Jeremy Leach]

And another idea, would be to take this graph, and approximate the curve by a set of straight lines, which could be used to get the result, by feeding in the Denominator value. i.e a lookup with interpolation. Not the easiest thing to code but definitely doable.

 

[golfnut]

Hi thx for the code

Hi, I run your code on sim for an hour or so and kind got in a mess,

I added a value to w10 of 4100 to simulate having a count from other HW



Symbol Ndiv = w10
Symbol Nmsw = w11
Symbol Nlsw = w12
Symbol Nresult = w13

let w10 = 4100


For Ndiv = 1330 To 4100

but it would not print the result as it didnt come out of the loop, after a few thousand loops.
Now I now your the dude on this stuff , so it aint you.
So cmon where and how bad did I mess up..

GN

 

[hippy]

It will run slowly and 'take forever' as it's a repeated subtraction but it appears to be working when I tried simulating. Perhaps post the code you've changed things to.

 

[marks]

Hi Golfnut,
try this too lol

w10=4092   '     number 1330 to 4100

w11=w10*3/10
w12=40000/w11*10

w14=40000//w11*10/w11
w15=40000//w11*10//w11
w15=w15*10/w11 :if w15>5 then  let w14= w14+1 :endif
w10=w12+w14

BINTOASCII w10,b8,b7,b6,b5,b4 

SERTXD (CR, LF, "",b9,b8,b7,b6,b5,b4,"  ", CR, LF)

 

[golfnut]

Hi Marks I tested your work and most of its great.

But some numbers dont work right.

e,g, 1333333/ count

if I enter denominator as count of 4040 the result is = 330 ok
if I enter denominator as count of 4050 the result is = 349 --- and it should be 329 ?

cheers
GN

 

[golfnut]

Hippy, Hi.

with you code I cut and pasted it.

Added

Symbol Nresult = w13

let Ndiv = 4032 'This part'

For Ndiv = 1330 To 4100

And I took the # off the ndiv on the serial out line..

I cant get it to exit the loop.
GN

 

[golfnut]

I caught a top gear episode and it had finished

Display red 1333333.33 1333333.33 13333333.33 .......

Im redoing it with the # back in

GN

 

[hippy]

with you code I cut and pasted it.

Added

Symbol Nresult = w13

let Ndiv = 4032 'This part'

For Ndiv = 1330 To 4100

And I took the # off the ndiv on the serial out line..

I cant get it to exit the loop.

Putting an "Ndiv=" before "For Ndiv=" will have absolutely no effect, the FOR will set Ndiv immediately overwriting the previous assignment. I've no idea why you took the # out; it is there for a reason

Using the simulator it appears that the variables are changing as I would expect but I didn't let it finish as I got bored waiting for it to complete. There will be numerous iterations before the loop does exit; 10,000 iterations for each result.

Say simulation does 10 iterations of the loop per second, 10,000 iterations will take 1,000 seconds; over 16 minutes. Longer if you don't have simulation running at the fastest speed. If you ran the entire program through simulation it would take over a month to complete.

Some things aren't suited to simulation, and this is one of them. That's also the reason the 20X2 is set to run at 64MHz; division by repeated subtraction can be incredibly slow especially with large enumerators and small divisors.

 

[golfnut]

Perhaps I worded my conundrom wrong from the outset,,

I will have a count -- I dont know what it will be , , but I know that the range of values will be approx what was stated 1332 to 4100 ish.

I will do a measure - somehow and get a count val as above - say 4000.

where shall I place my count number?

this Number has to get into the PICAXE and the code you kindly provided will pick it up and process it to give a result

i would be mega pleased if 4000 gave result output of 333

How long may this take on the real uprocessor - a few seconds max?

thanks again - for your support, time and effort. It is appreciated and it does turn projects I would have had to abandon into tangible learning kit..
GN

 

[marks]

Hi Golfnut,
can you please recheck your formula or maybe your reusing a variable somewhere.
I simulated 4050 with this program and it did return 329.
thanks marks

w10=4040'     number 1330 to 4100

w11=w10*3/10
w12=40000/w11*10

w14=40000//w11*10/w11
w15=40000//w11*10//w11
w15=w15*10/w11 :if w15>5 then  let w14= w14+1 :endif
w10=w12+w14

BINTOASCII w10,b8,b7,b6,b5,b4 
SERTXD (CR, LF, "",b9,b8,b7,b6,b5,b4,"  ", CR, LF)

after thinking about why you got a correct result for 4040 that is the value of w12(basic accuracy) ie w14 would be 0. (so you have a problem with adding w14 ).
info w14 improves accuracy of the count
w15 is the decimal part ie if > than 5(0.5) then 1 will be added to 14
hope this helps a bit lol.

for 4040 w12=330 w14=0 w15=0 ie (330.0)
for 4050 w12=320 w14=9 w15=2 ie(329.2)

 

[hippy]

This will calculate a single value; gives 1333333.33 / 4032 ~= 0330.6 on a real chip ...

#Picaxe 20X2
#No_Table
#No_data
#Terminal 9600

Symbol K       = 13333333
Symbol Kmsw    = K / $00010000
Symbol Klsw    = K & $0000FFFF

Symbol Ndiv    = w10
Symbol Nmsw    = w11
Symbol Nlsw    = w12
Symbol Nresult = w13

Ndiv = 4032

SetFreq M64

Nresult = 0
Nmsw    = Kmsw
Nlsw    = Klsw

Do while Nmsw <> 0 Or Nlsw >= Ndiv
  If Nlsw < Ndiv Then
    Nmsw = Nmsw - 1
  End If
  Nlsw = Nlsw - Ndiv
  Nresult = Nresult + 1
Loop

BinToAscii Nresult, b1,b2,b3,b4,b5

SetFreq M8

SerTxd( "1333333.33 / ", #Ndiv, " ~= ", b1,b2,b3,b4,".",b5, CR, LF )

 

[golfnut]

Hi Marks I ran your code again.

4050 comes out as ..

00349 on th serial output buffer window

maybe its a setting I dont have on my sim?

I have trouble displaying the simulated lcd too.
thanks for the code

hope you got the weather its 'toilet' here

GN

 

[golfnut]

code in HW

Thanks Hippy, takes about 3 seconds to do the math.

I gotta make a wombai counter and some opto devices

Then gotta work out how to get my counter 3byte wide No into picaxe!

thanks again..