Code generation for C/C++ in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to generate C code from a MATLAB function.

MATLAB

codegen -config:lib [1]

Drag options to blanks, or click blank then click option'

AmyFunction.c

BmyFunction.cpp

CmyFunction.m

DmyFunction.h

Attempts:

3 left

💡 Hint

Common Mistakes

Using a C or header file instead of the MATLAB function file.

Omitting the file extension.

The codegen command requires the MATLAB function file .m as input to generate C code.

2fill in blank

medium

Complete the code to specify the output type as a static library during code generation.

MATLAB

cfg = coder.config.[1]();

Drag options to blanks, or click blank then click option'

Amex

Bexe

Cdll

Dlib

Attempts:

3 left

💡 Hint

Common Mistakes

Using exe or dll instead of lib.

Confusing the configuration type with the output file extension.

The coder.config.lib() function creates a configuration object for generating a static library.

3fill in blank

hard

Complete the code to generate C code as a static library.

MATLAB

cfg = coder.config.[1]();
codegen -config cfg myFunc

Drag options to blanks, or click blank then click option'

Alib

Bdll

Cexe

Dmex

Attempts:

3 left

💡 Hint

Common Mistakes

Using exe or dll instead of lib.

Not creating a configuration object before setting properties.

The coder.config.lib() function creates a configuration object for generating a static library. Optimization is enabled by default.

4fill in blank

hard

Fill both blanks to generate C code for a function with input size specified.

MATLAB

args = [1];
codegen myFunc -args [2]

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A{1, 2, 3}

B[1, 2, 3]

C{[1, 2, 3]}

D[[1, 2, 3]]

Attempts:

3 left

💡 Hint

Common Mistakes

Using square brackets instead of curly braces for the cell array.

Not wrapping the input size vector inside a cell array.

The input arguments for codegen must be specified as a cell array containing the input sizes, e.g., {[1, 2, 3]}.

5fill in blank

hard

Fill all three blanks to configure code generation for a MATLAB function with custom output folder and build action.

MATLAB

cfg = coder.config.[1]();
cfg.GenerateReport = true;
cfg.OutputDir = '[2]';
cfg.Hardware.BuildAction = '[3]';
codegen -config cfg myFunc

Drag options to blanks, or click blank then click option'

Alib

Bexe

Cbuild

DbuildLib

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect configuration types.

Not using strings for output directory and build action.

Use lib to create a library configuration. The output directory can be any string, here exe is used as a folder name. The Hardware.BuildAction is a string like build to specify the build process.

Practice

1. What is the primary purpose of using codegen in MATLAB for C/C++?

easy

A. To visualize MATLAB data in 3D plots

B. To debug MATLAB scripts line by line

C. To create graphical user interfaces in MATLAB

D. To convert MATLAB code into C/C++ code for faster execution or integration

Solution

1. Step 1: Understand the role of codegen

   codegen is used to generate C/C++ code from MATLAB functions.

2. Step 2: Identify the main benefit

   This conversion helps in faster execution and easier integration with other C/C++ projects.

3. Final Answer:

   To convert MATLAB code into C/C++ code for faster execution or integration -> Option D

4. Quick Check:

   Code generation = convert MATLAB to C/C++ [OK]

Hint: Remember: codegen means generate code in C/C++ [OK]

Common Mistakes:

• Confusing codegen with debugging tools
• Thinking codegen creates plots
• Assuming codegen builds GUIs

2. Which of the following is the correct syntax to generate C code for a MATLAB function myFunc with input type double scalar?

easy

A. codegen myFunc -args {double(0)}

B. codegen myFunc -args {single(1)}

C. codegen myFunc -args {int32(1)}

D. codegen myFunc -args {1+0i}

Solution

1. Step 1: Understand input argument specification

   For codegen, input types are specified using MATLAB data types like double(0) for a scalar double.

2. Step 2: Check each option

   codegen myFunc -args {double(0)} uses double(0) which correctly specifies a double scalar input. Others either use incorrect syntax or values.

3. Final Answer:

   codegen myFunc -args {double(0)} -> Option A

4. Quick Check:

   Input type double scalar = double(0) [OK]

Hint: Use double(0) to specify a double scalar input [OK]

Common Mistakes:

• Using numeric literals directly without type
• Using curly braces incorrectly
• Confusing input value with input type

3. Given the MATLAB function

function y = squarePlusOne(x)
y = x.^2 + 1;
end

What will be the output C code function signature generated by codegen squarePlusOne -args {zeros(3,1)}?

medium

A. void squarePlusOne(const double x[3], double y[3])

B. double squarePlusOne(double x)

C. void squarePlusOne(double x, double *y)

D. double squarePlusOne(const double x[3])

Solution

1. Step 1: Analyze input argument

   The input is a 3x1 double vector, so the generated C function will take an array of 3 doubles as input.

2. Step 2: Determine output type

   The output is also a 3x1 vector, so the output is an array passed by reference.

3. Step 3: Match function signature

   void squarePlusOne(const double x[3], double y[3]) matches the expected signature: void function with input array and output array parameters.

4. Final Answer:

   void squarePlusOne(const double x[3], double y[3]) -> Option A

5. Quick Check:

   Array input/output = void func(const double x[3], double y[3]) [OK]

Hint: Array inputs generate functions with array parameters [OK]

Common Mistakes:

• Assuming scalar input/output signatures
• Missing const qualifier for input arrays
• Returning output instead of using output parameter

4. You try to generate C code for this MATLAB function:

function y = addVectors(a, b)
y = a + b;
end

using codegen addVectors -args {zeros(3,1), zeros(4,1)}. What is the main issue?

medium

A. Function syntax is incorrect for code generation

B. Input vectors have different sizes causing a code generation error

C. You must specify input types as integers, not doubles

D. codegen cannot handle vector inputs

Solution

1. Step 1: Check input argument sizes

   The inputs are vectors of sizes 3x1 and 4x1, which cannot be added element-wise due to size mismatch.

2. Step 2: Understand codegen requirements

   Code generation requires consistent input sizes for operations like addition.

3. Final Answer:

   Input vectors have different sizes causing a code generation error -> Option B

4. Quick Check:

   Size mismatch in inputs = error [OK]

Hint: Ensure input sizes match for element-wise operations [OK]

Common Mistakes:

• Ignoring input size mismatch
• Assuming codegen auto-resizes inputs
• Confusing data type with size issues

5. You want to generate C++ code from this MATLAB function that computes the sum of positive elements only:

function s = sumPositive(v)
s = sum(v(v > 0));
end

Which input argument specification is best for codegen to handle variable-length vectors?

hard

A. codegen sumPositive -args {double(0)}

B. codegen sumPositive -args {zeros(10,1)}

C. codegen sumPositive -args {coder.typeof(0,[Inf,1],[1,0])}

D. codegen sumPositive -args {coder.typeof(0,[10,1],[0,0])}

Solution

1. Step 1: Understand variable-size input specification

   To handle variable-length vectors, coder.typeof with [Inf,1] size and [1,0] variable-size flags is used.

2. Step 2: Evaluate options

   codegen sumPositive -args {coder.typeof(0,[Inf,1],[1,0])} correctly specifies a variable-length column vector of doubles. Others specify fixed sizes or scalars.

3. Final Answer:

   codegen sumPositive -args {coder.typeof(0,[Inf,1],[1,0])} -> Option C

4. Quick Check:

   Variable-size vector = coder.typeof with Inf size [OK]

Hint: Use coder.typeof with Inf size for variable-length inputs [OK]

Common Mistakes:

• Using fixed-size arrays for variable-length inputs
• Not setting variable-size flags correctly
• Confusing scalar input with vector input