Creating a new model in Simulink - Performance & Efficiency

Time Complexity: Creating a new model

O(n)

Understanding Time Complexity

When we create a new model in Simulink, we want to know how the time to set it up grows as the model gets bigger.

We ask: How does adding more parts affect the time it takes to build the model?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

% Create a new Simulink model
modelName = 'myModel';
new_system(modelName);
open_system(modelName);

% Add blocks in a loop
for i = 1:n
    add_block('simulink/Sources/Sine Wave', [modelName '/Sine' num2str(i)]);
end

% Save and close the model
save_system(modelName);
close_system(modelName);
    

This code creates a new model, adds n sine wave blocks, then saves and closes it.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Adding blocks inside the for-loop.
• How many times: The loop runs n times, once for each block added.

How Execution Grows With Input

Each time we add a block, the work increases by one unit. So if we add more blocks, the time grows steadily.

Input Size (n)	Approx. Operations
10	10 block additions
100	100 block additions
1000	1000 block additions

Pattern observation: The time grows directly with the number of blocks added.

Final Time Complexity

Time Complexity: O(n)

This means the time to create the model grows in a straight line as you add more blocks.

Common Mistake

[X] Wrong: "Adding blocks happens instantly no matter how many blocks there are."

[OK] Correct: Each block takes some time to add, so more blocks mean more time, not zero extra time.

Interview Connect

Understanding how adding parts to a model affects time helps you explain efficiency clearly and shows you can think about scaling in real projects.

Self-Check

"What if we added blocks in nested loops, creating groups of blocks? How would the time complexity change?"

Practice

1. What is the first step to create a new model in Simulink?

easy

A. Use new_system to create a new model.

B. Use simulink.open_system to open an existing model.

C. Add blocks directly without creating a model.

D. Save the model before creating it.

Solution

1. Step 1: Understand model creation functions

   The function new_system is used to create a new empty model in Simulink.

2. Step 2: Differentiate from opening models

   open_system opens existing models but does not create new ones.

3. Final Answer:

   Use new_system to create a new model. -> Option A

4. Quick Check:

   New model creation = new_system [OK]

Hint: Remember: new_system creates, open_system opens [OK]

Common Mistakes:

• Confusing new_system with open_system
• Trying to add blocks before creating a model
• Assuming saving creates a model

2. Which of the following is the correct syntax to create and open a new Simulink model named 'myModel'?

easy

A. simulink.create_system('myModel'); simulink.show_system('myModel');

B. simulink.open_system('myModel'); simulink.new_system('myModel');

C. new_system('myModel'); open_system('myModel');

D. simulink.new_system('myModel'); simulink.open_system('myModel');

Solution

1. Step 1: Identify correct function names

   The correct functions are new_system to create and open_system to open the model.

2. Step 2: Check function order and syntax

   Create the model first, then open it. new_system('myModel'); open_system('myModel'); follows this order and uses correct function names and syntax.

3. Final Answer:

   new_system('myModel'); open_system('myModel'); -> Option C

4. Quick Check:

   Create then open = new_system('myModel'); open_system('myModel'); [OK]

Hint: Create first, then open with correct function names [OK]

Common Mistakes:

• Using open_system before new_system
• Using incorrect function names like create_system
• Using incorrect 'simulink.' prefix

3. What will be the output of the following code snippet?

modelName = 'testModel';
new_system(modelName);
open_system(modelName);
blocks = find_system(modelName, 'Type', 'Block');
numBlocks = length(blocks);

What is the value of numBlocks right after running this code?

medium

A. 0

B. 1

C. An error occurs because the model is empty

D. Undefined variable error

Solution

1. Step 1: Understand model creation and block count

   After creating and opening a new model, it contains no blocks by default.

2. Step 2: Use find_system to count blocks

   find_system with 'Type'='Block' returns all blocks. Since none are added, the list is empty, so length is 0.

3. Final Answer:

   0 -> Option A

4. Quick Check:

   New model has zero blocks [OK]

Hint: New model starts empty, so block count is zero [OK]

Common Mistakes:

• Assuming default blocks exist
• Expecting an error for empty model
• Confusing blocks with system components

4. Consider this code snippet:

open_system('newModel');
new_system('newModel');

What is the main issue with this code when creating a new model?

medium

A. There is no issue; this code works fine.

B. The model is created twice, wasting memory.

C. The model name is invalid for Simulink.

D. The model is opened before it is created, causing an error.

Solution

1. Step 1: Analyze function order

   The code tries to open a model named 'newModel' before creating it, which causes an error because the model does not exist yet.

2. Step 2: Understand correct sequence

   The correct sequence is to create the model first with new_system, then open it.

3. Final Answer:

   The model is opened before it is created, causing an error. -> Option D

4. Quick Check:

   Open before create causes error [OK]

Hint: Always create before opening a model [OK]

Common Mistakes:

• Opening a model before creation
• Assuming open_system creates the model
• Ignoring error messages

5. You want to programmatically create a new Simulink model named 'controlSystem', add a Gain block, and open the model for editing. Which sequence of commands correctly achieves this?

hard

A. simulink.open_system('controlSystem'); add_block('simulink/Commonly Used Blocks/Gain', 'controlSystem/Gain1'); simulink.new_system('controlSystem');

B. new_system('controlSystem'); add_block('simulink/Commonly Used Blocks/Gain', 'controlSystem/Gain1'); open_system('controlSystem');

C. add_block('simulink/Commonly Used Blocks/Gain', 'controlSystem/Gain1'); simulink.new_system('controlSystem'); simulink.open_system('controlSystem');

D. simulink.new_system('controlSystem'); simulink.open_system('controlSystem'); add_block('simulink/Commonly Used Blocks/Gain', 'controlSystem/Gain1');

Solution

1. Step 1: Create the new model first

   Use new_system('controlSystem') to create the model before adding blocks.

2. Step 2: Add the Gain block to the model

   Use add_block with the correct source and destination path inside the new model.

3. Step 3: Open the model for editing

   Finally, open the model window with open_system('controlSystem') to see and edit it visually.

4. Final Answer:

   new_system('controlSystem'); add_block('simulink/Commonly Used Blocks/Gain', 'controlSystem/Gain1'); open_system('controlSystem'); -> Option B

5. Quick Check:

   Create, add block, then open model [OK]

Hint: Create model, add blocks, then open model [OK]

Common Mistakes:

• Adding blocks before creating the model
• Opening model before adding blocks
• Incorrect block path in add_block