Best pratice for working with floating constants

Dear Kevin,

in my opinion your solution is the best and easiest way to use FLOAT values in calculations within VA. At least this is the way I have been using for many years now

As you did in your example, it is always recommended to work with bitshifts instead of multiplying the values by a power of ten for example. So, after calculation you can get rid of the fractional bits by a simple bitshift and you don't need to use the division operator, that can be very expensive regarding FPGA resources.

Greetings,

Oliver

Dear Kevin,

Thank you for your precise question.
There is one kind of valid float values you can use: ParameterTranslations...

In VA native(FPGA) processing you will need to use fixed point arithmetics.

Quote from kevinh

I am fairly new to VA and was wondering how to work with floating constants that I need in my computation.

Below you can find a simple example into fixed point arithmetics:

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The ShiftLeft will give you precision (here 10 bit) and I recommend RND to reduce to lower precision.
ShiftLeft by 10 bit will give you a resolution of 10bit = 1024 steps in between two integer values.
When you require more, use more bits...

Best regards,

Quote from kevinh

floating numbers in VA

The following details will help you to implement floating point into the software interface:

ParameterTranslation:

https://docs.baslerweb.com/liv…FloatParamTranslator.html
Formula Syntax: Mathematical Operations
The syntax complies to the GenICam API standard in version 2.0. The allowed formula elements are identical to the formula elements defined in the GenICam standard:
Basic operations:
()	brackets
+ - * /	addition, subtraction, multiplication, division
%	remainder
**	power
& | ^ ~	bitwise: and / or / xor / not
<> = > < <= >=	logical relations: not equal / equal / greater / less / less or equal / greater or equal
&&	logical and / logical or
<< >>	shift left / shift right
Basic operations Conditional operator <condition> ? <true_expr> : <false_expr>	Example: ${target.Value} = (${this.Value} > 0) ? 1 : 0;
Functions:
SGN(x)	return sign of x. Returns +1 for positive argument and -1 for negative argument
NEG(x)	swap sign of x
ABS(x)	return absolute value of x
SQRT(x)	return square root of x
TRUNC(x)	truncate x, which means returning the nearest integral value that is not larger in magnitude than x
FLOOR(x)	Round downward, returning the largest integral value that is not greater than x
CEIL(x)	Round upward, returning the smallest integral value that is not less than x
ROUND(x,precision)	round x to the number of decimal fractional digits given by precision, with halfway cases rounded away from zero
SIN(x)	return sine of an angle of x radians
COS(x)	return cosine of an angle of x radians
TAN(x)	return the tangent of an angle of x radians
ASIN(x)	return the principal value of the arc sine of x, expressed in radians
ACOS(x)	return the principal value of the arc cosine of x, expressed in radians
ATAN(x)	return the principal value of the arc tangent of x, expressed in radians
EXP(x)	return the base-e exponential function of x, which is e raised to the power x: ex
LN(x)	return the natural logarithm of x The natural logarithm is the base-e logarithm: the inverse of the natural exponential function (exp).
LG(x)	return the common (base-10) logarithm of x
E()	return Euler's number, 2.7182818284590451
PI()	return circle constant, 3.1415926535897931
Functions Example: ${target.Value} = NEG(${this.Value})
Access to Parameter Properties
The formulas can not only incorporate the values of parameters, but also specific properties of parameters, such as minimal value, maximal value, or step size:
${PathToModule/Module.ParamName.From} or ${PathToModule/Module.ParamName.Min}: minimal valid value of parameter PathToModule/Module.ParamName.
${PathToModule/Module.ParamName.To} or ${ PathToModule/Module.ParamName.Max}: maximum valid value of parameter PathToModule/Module.ParamName.
${PathToModule/Module.ParamName.Inc}: Increment (step size) between two valid values of parameter PathToModule/Module.ParamName.
${PathToModule/Module.ParamName.Enum("EnumName")}: Integer value of enumeration name EnumName.

Best regards,

Look here for a similar topic:

Sqrt operation for bit widths bigger than 32

Best regards,

In addition to the great posts above for the use of fixed point arithmetic:

Notation: u(5,3) means unsigned, 5 integer and 3 fractional bits.

There is a simple rule for fixed point arithmetic.

For additions or subtractions you need to use the same number of fractional bits at the input. The result will have the same number of fractional bits. Integer bits will increase by one.

So u(5,3) + u(9,3) will become u(10,3)

e.g. 1.5 + 2.25 = 3.75 --> 12 + 18 = 30

For multiplications and division the number of fractional bits at the inputs can differ. For multiplications the resulting fractional bits will be the sum of the input fractional bits. The resulting integer bits will be the sum of the input integer bits.

So u(5,3) * u(2,8) will become u(7,11)

e.g. 1.5 * 2.25 = 3.375 --> 12 * 576 = 6912

Johannes

Dear Johannes,

I would like to add one detail on the fractional bits:

Quote from Johannes Trein

Notation: u(5,3) means unsigned, 5 integer and 3 fractional bits.

In case of using 3 fractional bits, there will be 2³ values betreen two integer values:

Using 3 fractional bits will represent 2³ = 8 steps.

Each step in fixed point granularity : 1/8 = 0.125

Best regards,

Hi Kevin,

Quote from kevinh

I am hoping to get some feedback and insights on how to work with floating numbers in VA this way and maybe help others facing the same problem.

Could the posts above solve/answer your problem/question?

Best regards,