1.3 How Write and Analyze Algorithm

Understanding Algorithm Writing and Analysis

Introduction to Algorithm Writing

• The speaker discusses the process of writing a new program, emphasizing that they are focusing on algorithms rather than complete programs.

• It is noted that data types and parameter declarations are not considered in algorithm writing, as these details are typically addressed during actual programming.

Syntax Flexibility in Algorithms

• The speaker highlights the flexibility in syntax when writing algorithms, mentioning alternative symbols for assignment used in various programming languages like Pascal.

• Emphasis is placed on clarity; whatever syntax is chosen should be understandable to all stakeholders involved in the project.

Criteria for Analyzing Algorithms

• The first criterion for analyzing an algorithm is its efficiency, particularly how much time it takes to execute.

• Time efficiency is crucial; lengthy procedures can hinder performance while faster methods yield quicker results.

Time and Space Complexity

• After determining time efficiency, space complexity must also be analyzed—how much memory the algorithm will consume during execution.

• Additional criteria may include data transfer requirements and power consumption, especially relevant for modern handheld devices.

Further Considerations in Algorithm Design

• Other factors such as network consumption and CPU usage are important when developing algorithms for specific applications or device drivers.

• The speaker notes that understanding register usage within CPUs can also influence algorithm design decisions.

Example of Time Analysis

• An example is provided to illustrate time analysis; each statement in an algorithm generally takes one unit of time.

• A simple calculation shows that if an algorithm consists of three statements, it would take three units of time to execute.

Complexity Evaluation

• When evaluating more complex statements (e.g., involving multiplication or addition), it's acknowledged that while each operation might seem straightforward, machine-level translation complicates this analysis.

Analysis of Detailed Planning in Problem Solving

Importance of Detail in Analysis

• The speaker emphasizes the necessity of detailed analysis, likening it to planning a journey. Unlike casual travel, complex tasks require thorough preparation and understanding.

• For significant missions, such as landing on Mars, one cannot simply rely on basic tools; extensive planning and design are crucial for success.

Levels of Analysis

• The discussion highlights that while a basic level of analysis will be conducted, deeper exploration is possible depending on requirements.

• The speaker identifies three variables involved in the space analysis: two parameters (P and another unspecified parameter) and one local variable.

Constants in Space Analysis

• Each variable is treated as a unit of time or "word," indicating that regardless of their numerical value (e.g., 3 or 3000), they are represented consistently as constants within the analysis framework.