Calculation Problem - value goes to zero after 65

[Ingvar]

Hi Darrel,

Isn't it wonderful when we try to improve the accuracy with about half a ppm .... and the world has hardly descided how long a nautical mile really is. I got "1 knot = 1.15078030303 mph" from http://www.geocities.com/TheTropics/...311/ktmph.html , but after doing a little more digging around, i now agree with you. It shows that you can't really trust anything you find on the net.

BTW, i really like the way you do the rounding, i can imagine that beeing speedy in assembler ....... i just might steal it sometime ;-)

Just to be a pain, i'll show how i'd do this calculation with rounding(and adding that extra little accuracy). Perhaps someone will find it useful.

Dec_speed = ((Dec_speed */ 2946) + 5) / 10

It's probably a little slower than your method since it involves a division.

/Ingvar

[Darrel Taylor]

Ingvar,

OK, now we're getting silly, but I just can't resist.

Same thing as before, With Rounding, less code.

Dummy = Dec_speed * 9881
Dec_speed = R0 + R2.15 + Dec_speed

Saved 30 Words in the process.

OK, I'll quit now,
   Darrel

[Ingvar]

While were on the task of reducing and optimizing Toms code, i feel a strong urge to reduce .......

SSD4= (ssmax[18]>>4)
SSD3= (ssmax[18] & $f)
SSD2= (ssmax[17]>>4)
SSD1= (ssmax[17] & $f)

Then convert to Decimal:
Dec_speed=(ssd4*4096)+(ssd3*256)+(ssd2*16)+ssd1 ' convert to dec

..... into .....

Dec_speed.HighByte = ssmax[18]
Dec_speed.LowByte = ssmax[17]

...... thus saving time, codespace and ram ... you name it.

How about it Darrel, want a shot at it ;-)

[Darrel Taylor]

Good eye Ingvar,

I didn't even notice that he was Ripping them apart, just to re-assemble them back exactly like they were. That's a pretty big code savings.

And, here's my "Shot at it"

@Dec_Speed = _ssmax + 17
Dec_Speed   VAR  WORD  EXT

Zero Code.

Think we can reduce it even farther??

Darrel

[Dwayne]

Hello Darrell,,


Darrell>>Zero Code.

Think we can reduce it even farther?? <<


There goes the bankruptsy of Pkzip....

Dwayne

[Ingvar]

Ouch, i believe your "Shot at it" found it's target ..... sinking .... mayday. It's difficult to beat zero code, really difficult ...... sort of impossible.

However, i want to point out that if you change the value of "Dec_Speed" you infact change the values in the array(ssmax17&18). This makes it impossible to use for other tasks, not a problem in this application(i hope). I bet you know that but some people find it difficult to get their head around this.

Good job!

/Ingvar

[Darrel Taylor]

All true, I guess it's Bad Form to re-use variables like that.

So here it is. The End all, Be all solution to Tom's Knot to MPH conversion.

@Knots = _ssmax + 17
Knots    VAR  WORD  ext

Dec_speed = Knots * 9881
Dec_speed = R0 + R2.15 + Knots

That way it preserves the original Knots value and calculates Dec_speed from it.

Ok, now I really quit.

Darrel