MATLAB Programming

11 Improving Performance and Memory Usage
Assigning Real and Complex Numbers
Assigning a complex number to a variable that already holds a real number
impacts the performance of your program. Similarly, you should not assign a
realvaluetoavariablethatalreadyholdsacomplexvalue.
OperatingonRealData
When operating on real (i.e., noncomplex) numbers, it is more efficient to use
MATLAB functions that have been designed specifically for real numbers.
The following functions return numeric values that are real.
Function
reallog
realpow
realsqrt
Description
Find natural logarithm for nonnegative real arrays
Find array power for real-only output
Find square root for nonnegative real arrays
Using Appropriate Logical Operators
When performing a logical AND or OR operation, you have a choice of two
operators of each type.
Operator
&, |
&&, ||
Description
Perform logical AND and OR on arrays element by
element
Perform logical AND and OR on scalar values with
short-circuiting
In if and while statements, it is more efficient to use the short-circuiting
operators, && for logical AND and || for logical OR. This is because these
operators often don’t have to evaluate the entire logical expression. For
example, MATLAB evaluates only the first part of this expression whenever
the number of input arguments is less than three:
if (nargin >= 3) && (ischar(varargin{3}))
See Short-Circuit Operators in the MATLAB documentation for a discussion
on short-circuiting with && and ||.
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