32-bit Multiplication Question

Archiver

I had been looking around ways to do 32-bit multiplication with BS2.
Most of the solutions I found only display the upper 32-bit Word for
display purposes using Debug like the following:

ValueX VAR Word
ValueY VAR Word
ValueZ0 VAR Word
VAlueZ1 VAR Word

DO
DEBUG "Value1:"
DEBUGIN HEX4 ValueX
DEBUG CR
DEBUGIN HEX4 ValueY
DEBUG CR

ValueZ0 = ValueX * ValueY
ValueZ1 = ValueY ** ValueY

DEBUG HEX4 ValueX," * ",HEX4 ValueY," = ",HEX4 ValueZ1,HEX4 ValueZ0

What I really want is to work with it rather than just displaying like
the following:

ValueX = 700
ValueY = (ValueX * 1000) / 900

In the real world that would give me 777.7.... But in BS2 if I
multiply 700 * 1000, that would exceed the 16-bit limit. I don't want
to multiply it by 10 or 100. I need more precision. As you can see my
final value that I was looking for is still 16-bit even though I can't
get fractions in BS2 but I'm still happy with 777.

- Johari

Archiver

Johari

I've posted double and quad precision multiply and divide examples at:
http://www.emesystems.com/BS2math6.htm

You have to still have to watch out for the scaling of the variables.
It depends on what you want to do.

Al Williams offers a floating point math coprocessor chip.

-- regards
Tracy Allen
electronically monitored ecosystems
http://www.emesystems.com
mailto:tracy@e...


>I had been looking around ways to do 32-bit multiplication with BS2.
>Most of the solutions I found only display the upper 32-bit Word for
>display purposes using Debug like the following:
>
>ValueX VAR Word
>ValueY VAR Word
>ValueZ0 VAR Word
>VAlueZ1 VAR Word
>
>DO
>DEBUG "Value1:"
>DEBUGIN HEX4 ValueX
>DEBUG CR
>DEBUGIN HEX4 ValueY
>DEBUG CR
>
>ValueZ0 = ValueX * ValueY
>ValueZ1 = ValueY ** ValueY
>
>DEBUG HEX4 ValueX," * ",HEX4 ValueY," = ",HEX4 ValueZ1,HEX4 ValueZ0
>
>What I really want is to work with it rather than just displaying like
>the following:
>
>ValueX = 700
>ValueY = (ValueX * 1000) / 900
>
>In the real world that would give me 777.7.... But in BS2 if I
>multiply 700 * 1000, that would exceed the 16-bit limit. I don't want
>to multiply it by 10 or 100. I need more precision. As you can see my
>final value that I was looking for is still 16-bit even though I can't
>get fractions in BS2 but I'm still happy with 777.
>
>- Johari
>
>
>
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Archiver

>ValueX = 700
>ValueY = (ValueX * 1000) / 900
>
>In the real world that would give me 777.7.... But in BS2 if I
>multiply 700 * 1000, that would exceed the 16-bit limit. I don't want
>to multiply it by 10 or 100. I need more precision. As you can see my
>final value that I was looking for is still 16-bit even though I can't
>get fractions in BS2 but I'm still happy with 777.
>
>- Johari


For that example, where 1000 and 900 are constants, the multiplier is 10/9, so
X=700
y=X * 10/9
debug dec y,cr
can be done by the Stamp and prints an answer of 777.

If you need one more digit of precision you can do,
X=700
y = (X * 10/9 *10) + (X*10//9 *10 /9)
debug dec y/10,".",dec1 y,cr

which prints 777.7

Another way to do it is to use the ** operator, which works with a 32
bit intermediate result.

X=700
y = X + (X ** 7282) ' 1/9 = 7282/65536
debug dec y,cr ' prints 777

or for more precision,
y = X*10 + (X*2**36409) '
debug dec y/10,".",dec1 y,cr ' prints 777.7

The ** method works even when the constants are not simple like 10/9,
for example, 1023/917 = 1.1156.

If the other values are also variables, not constants, then you have
to fall back on true double precision methods.
more on ** and multiply by constant at
http://www.emesystems.com/BS2math1.htm
and more on double precision at
http://www.emesystems.com/BS2math6.htm


-- Tracy