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Understand why data structures matter through memory systems
Section 1 of 4
Discover how memory access patterns can make the difference between milliseconds and minutes in program execution.
Time: 1-3 CPU cycles
When: Data is already in CPU cache
Example: Sequential array access
Time: 200-300 CPU cycles
When: Data must be loaded from RAM
Example: Random memory access
Time: Millions of CPU cycles
When: Data must be loaded from disk
Example: Virtual memory page fault
Task: Sum 1 million integers
Array: ~2ms (sequential)
Linked List: ~50ms (random)
25x slower!
Good hash: O(1) lookups
Bad hash: O(n) lookups
Impact: 1000x slower for large datasets
Choose wisely!
Indexed: Milliseconds
Full scan: Minutes/Hours
B-trees: Enable fast lookups
Index everything!
The choice of data structure and access pattern can make the difference between a program that runs in milliseconds versus one that takes hours. Understanding these performance characteristics is crucial for writing efficient software.