Main Content

fimath Properties

Properties of the fimath object

expand all in page

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

expand all

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.

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

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

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.

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.

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.

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

Note

SumSlope=SumSlopeAdjustmentFactor×2SumFixedExponent

Changing one of these properties affects the others.

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=SumSlopeAdjustmentFactor×2SumFixedExponent

Changing one of these properties affects the others.

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

Product Data Type Properties

expand all

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

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

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.

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.

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.

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

Note

ProductSlope=ProductSlopeAdjustmentFactor×2ProductFixedExponent

Changing one of these properties affects the others.

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×2ProductFixedExponent

Changing one of these properties affects the others.

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

Rounding and Overflow Properties

expand all

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.

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