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cost

Estimate cost of implementing filter System object

Description

example

c = cost(sysobj) returns a structure, c, whose fields contain information about the computational cost of implementing the filter System object™, sysobj.

c = cost(sysobj,'Arithmetic',arithType) returns a cost estimate c for the filter System object sysobj in the arithmetic specified by arithType.

Examples

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This example shows how to compute the cost of implementing an FIR Filter created using dsp.FIRFilter object.

Fs = 8000; Fcutoff = 2000;
firFilt = dsp.FIRFilter('Numerator', fir1(130,Fcutoff/(Fs/2)));
cost(firFilt)
ans = struct with fields:
                  NumCoefficients: 131
                        NumStates: 130
    MultiplicationsPerInputSample: 131
          AdditionsPerInputSample: 130

Input Arguments

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Arithmetic used in the filter analysis, specified as 'double', 'single', or 'Fixed'. When the arithmetic input is not specified and the filter System object is unlocked, the analysis tool assumes a double-precision filter. When the arithmetic input is not specified and the System object is locked, the function performs the analysis based on the data type of the locked input.

The 'Fixed' value applies to filter System objects with fixed-point properties only.

When the 'Arithmetic' input argument is specified as 'Fixed' and the filter object has the data type of the coefficients set to 'Same word length as input', the arithmetic analysis depends on whether the System object is unlocked or locked.

  • unlocked –– The analysis object function cannot determine the coefficients data type. The function assumes that the coefficients data type is signed, has a 16-bit word length, and is auto scaled. The function performs fixed-point analysis based on this assumption.

  • locked –– When the input data type is 'double' or 'single', the analysis object function cannot determine the coefficients data type. The function assumes that the data type of the coefficients is signed, has a 16-bit word length, and is auto scaled. The function performs fixed-point analysis based on this assumption.

To check if the System object is locked or unlocked, use the isLocked function.

When the arithmetic input is specified as 'Fixed' and the filter object has the data type of the coefficients set to a custom numeric type, the object function performs fixed-point analysis based on the custom numeric data type.

Output Arguments

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Cost estimate, c contains the following fields:

Estimated Value

Description

NumCoefficients

Number of filter coefficients (excluding coefficients with values 0, 1 or -1)

NumStates

Number of filter states

MultiplicationsPerInputSample

Number of multiplication operations performed for each input sample

AdditionsPerInputSample

Number of addition operations performed for each input sample

Introduced in R2011a