fimath Properties

Properties of the fimath object

fimath properties determine the rules for performing fixed-point arithmetic operations on fi objects. fimath properties are, by transitivity, also properties of the fi object. You can set these properties for individual fi objects. fimath object properties are always writable.

Sum Data Type Properties

CastBeforeSum — Whether both operands are cast to the sum data type before addition

0 (false) (default) | 1 (true)

Whether both operands are cast to the sum data type before addition, specified as one of these values:

• 0 (false) — Do not cast before sum

• 1 (true) — Cast before sum

Note

This property is hidden when the SumMode is set to FullPrecision.

MaxSumWordLength — Maximum allowable word length for the sum data type

65535 (default) | positive integer

Maximum allowable word length for the sum data type, specified as a positive integer.

SumBias — Bias of the sum data type

0 (default) | floating-point number

Bias of the sum data type, specified as a floating-point number.

SumFixedExponent — Fixed exponent of the sum data type

-30 (default) | positive or negative integer

Fixed exponent of the sum data type, specified as a positive or negative integer.

Note

The SumFractionLength is the negative of the SumFixedExponent. Changing one property changes the other.

SumFractionLength — Fraction length of the sum data type in bits

30 (default) | positive or negative integer

Fraction length of the sum data type in bits, specified as a positive or negative integer.

Note

The SumFractionLength is the negative of the SumFixedExponent. Changing one property changes the other.

SumMode — How the sum data type is determined

FullPrecision (default) | KeepLSB | KeepMSB | SpecifyPrecision

How the sum data type is determined, specified as one of the following:

• FullPrecision — Keep the full precision of the result.

• KeepLSB — Keep least significant bits. Specify the sum data type word length, while the fraction length is set to maintain the least significant bits of the sum.

• KeepMSB — Keep most significant bits. Specify the sum data type word length, while the fraction length is set to maintain the most significant bits of the sum and no more fractional bits than necessary.

• SpecifyPrecision — Specify the word and fraction lengths or the slope and bias of the sum data type.

SumSlope — Slope of the sum data type

9.3132e-010 (default) | floating-point number

Slope of the sum data type, specified as a floating-point number.

Note

$$SumSlope\text{=}SumSlopeAdjustmentFactor\times 2^{SumFixedExponent}$$

Changing one of these properties affects the others.

SumSlopeAdjustmentFactor — Slope adjustment factor of the sum data type

1 (default) | floating-point number greater than or equal to 1 and less than 2

Slope adjustment factor of the sum data type, specified as a floating-point number greater than or equal to 1 and less than 2.

Note

$$SumSlope\text{=}SumSlopeAdjustmentFactor\times 2^{SumFixedExponent}$$

Changing one of these properties affects the others.

SumWordLength — Word length of the sum data type in bits

32 (default) | positive integer

Word length of the sum data type in bits, specified as a positive integer.

Product Data Type Properties

MaxProductWordLength — Maximum allowable word length for the product data type

65535 (default) | positive integer

Maximum allowable word length for the product data type, specified as a positive integer.

ProductBias — Bias of the product data type

0 (default) | floating-point number

Bias of the product data type, specified as a floating-point number.

ProductFixedExponent — Fixed exponent of the product data type

-30 (default) | positive or negative integer

Fixed exponent of the product data type, specified as a positive or negative integer.

Note

The ProductFractionLength is the negative of the ProductFixedExponent. Change one property changes the other.

ProductFractionLength — Fraction length of the product data type in bits

30 (default) | positive or negative integer

Fraction length of the product data type in bits, specified as a positive or negative integer.

Note

The ProductFractionLength is the negative of the ProductFixedExponent. Changing one property changes the other.

ProductMode — How the product data type is determined

FullPrecision (default) | KeepLSB | KeepMSB | SpecifyPrecision

How the product data type is determined, specified as one of these values:

• FullPrecision — Keep the full precision of the result.

• KeepLSB — Keep least significant bits. Specify the product word length, while the fraction length is set to maintain the least significant bits of the product.

• KeepMSB — Keep most significant bits. Specify the product word length, while the fraction length is set to maintain the most significant bits of the product.

• SpecifyPrecision — Specify the word and fraction lengths or slope and bias of the product.

ProductSlope — Slope of the product data type

9.3132e-010 (default) | floating-point number

Slope of the product data type, specified as a floating-point number.

Note

$$ProductSlope=ProductSlopeAdjustmentFactor\times 2^{ProductFixedExponent}$$

Changing one of these properties affects the others.

ProductSlopeAdjustmentFactor — Slope adjustment factor of the product data type

1 (default) | floating-point number greater than or equal to 1 and less than 2

Slope adjustment factor of the product data type, specified as a floating-point number greater than or equal to 1 and less than 2.

Note

$$ProductSlope=ProductSlopeAdjustmentFactor\times 2^{ProductFixedExponent}$$

Changing one of these properties affects the others.

ProductWordLength — Word length of the product data type in bits

32 (default) | positive integer

Word length of the product data type in bits, specified as a positive integer.

Rounding and Overflow Properties

OverflowAction — Action to take on overflow

Saturate (default) | Wrap

Action to take on overflow, specified as one of these values:

• Saturate — Saturate to maximum or minimum value of the fixed-point range on overflow.

• Wrap — Wrap on overflow. This mode is also known as two's complement overflow.

RoundingMethod — Rounding method to use

Nearest (default) | Ceiling | Convergent | Zero | Floor | Round

Rounding method to use, specified as one of the following:

• Nearest — Round toward nearest. Ties round toward positive infinity.

• Ceiling — Round toward positive infinity.

• Convergent — Round toward nearest. Ties round to the nearest even stored integer (least biased).

• Zero — Round toward zero.

• Floor — Round toward negative infinity.

• Round — Round toward nearest. Ties round toward negative infinity for negative numbers, and toward positive infinity for positive numbers.

Version History

Introduced before R2006a