# Algorithmic thinking

## ## Learning Objectives

By the end of this lesson, students will be able to:

- Apply algorithmic thinking to solve engineering problems using computational tools.
- Translate engineering problems into structured programming logic.
- Use software tools to implement, test, and refine engineering solutions.

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## 1. Define the Problem

In many fields of engineering we must. Before writing code or building models, clearly define the engineering problem.

- **List knowns and unknowns.** What inputs are given? What outputs are required?
    
- **Establish system constraints and assumptions.** Identify physical laws, design requirements, and performance limits.
    
- **Clarify computational objectives.** What are you trying to calculate, simulate, or optimize?
    

**Example:** Given force and displacement data from a materials test, write a program to compute and plot stress-strain behavior.

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## 2. Develop a Strategy

To think algorithmically, break the problem into logical steps that a computer can follow.

- **Define the inputs and outputs.** What variables will the program take in, and what results will it produce?
- **Break the problem into sub-tasks.** Identify steps such as data input, processing, and visualization.
- **Outline the algorithm.** Write pseudocode or flowcharts that describe the computational steps.
- **Identify patterns or formulas.** Can loops, conditionals, or equations be used to automate parts of the solution?
    

**Example:** For processing stress-strain data:

1. Import data from a file.
2. Convert force and displacement to stress and strain.
3. Plot the stress-strain curve.
4. Identify the yield point or modulus.
    

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## 3. Execute the Code

- **Choose the right tools.** Use Python, MATLAB, or similar platforms.
- **Write modular code.** Use functions to separate different tasks (e.g., reading data, computing values, plotting).
- **Check for syntax and logic errors.** Debug line-by-line using print statements or a debugger.

**Example:** Write a Python script that uses NumPy and Matplotlib to load a CSV file, compute stress and strain, and generate plots.

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## 4. Test and Validate

- **Run test cases.** Use small inputs with known outputs to check correctness.
- **Compare with theoretical or experimental results.** Does the output match expected behavior?
- **Check units and scaling.** Ensure computations are consistent with physical meaning.

**Example:** If your plot shows stress values in the thousands when you expect hundreds, check unit conversions in your formula.

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## 5. Refine and Optimize

- **Improve readability and efficiency.** Refactor code to use vectorized operations or clearer variable names.
- **Add flexibility.** Allow the user to change input files or parameters without modifying code.
- **Document the process.** Include comments and a user guide.

**Example:** Upgrade your script so that it can analyze any stress-strain dataset provided in a CSV file with minimal setup.

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## 6. Troubleshooting Strategies

When your code doesn’t work as expected:

- **Isolate the error.** Use print statements or breakpoints to trace the bug.
- **Check assumptions.** Are inputs being read correctly? Are formulas implemented correctly?
- **Consult documentation.** Use official libraries’ documentation or community resources like Stack Overflow.

**Example:** If an array is returning NaN values, check whether division by zero is occurring or if missing data is in the input file.

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## 7. Case Study: Simulating a Spring-Mass System

**Scenario:** Model the motion of a mass-spring-damper system using a numerical solver.

1. **Define the Problem:** Set up the differential equation from Newton’s Second Law.
2. **Develop a Strategy:** Discretize time, apply numerical integration (e.g., Euler or Runge-Kutta).
3. **Execute the Code:** Write a Python function that computes motion over time.
4. **Test the Model:** Compare results with analytical solutions for undamped or lightly damped systems.
5. **Refine the Model:** Add adjustable damping and stiffness parameters.
6. **Troubleshoot Issues:** If the model becomes unstable, reduce the time step or use a more accurate integrator.

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## Summary

To solve engineering problems with computers:

1. **Define the problem and computational goals.**
2. **Develop an algorithmic strategy.**
3. **Implement the solution in code.**
4. **Test and validate with known cases.**
5. **Refine the code and enhance usability.**
6. **Troubleshoot and learn from failures.**

With algorithmic thinking and the right tools, engineers can automate analysis, simulate systems, and make data-driven decisions more efficiently.

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## 4. Verify and Interpret Results

- **Assess the feasibility of your results.** Do the values align with expected physical behavior?
- **Compare against established benchmarks.** Validate solutions using experimental data, literature values, or known theoretical limits.
- **Conduct a sensitivity analysis.** Examine how slight variations in input parameters influence the outcome.

**Example:** If a rocket nozzle expansion ratio results in an unrealistic exit velocity, revisit the assumptions regarding isentropic flow and compressibility effects.