Module 1: Memory & Efficiency

Course Navigation

Understand why data structures matter through memory systems

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25 minutes

Foundations of DSA

Memory & EfficiencyCurrent

Arrays & Memory Fundamentals

Stacks & Queues

Linked Lists

Trees & Hierarchical Structures

Graph Theory & Algorithms

Hash Tables & Hashing

Dynamic Programming

Sorting & Searching

Module Progress

Section 1 of 4

Module Stats

Total Sections:4

Estimated Time:25 minutes

Difficulty:Beginner

Progress:0%

Memory Hierarchy & Performance

Computer MemoryHierarchy

Understanding the speed-capacity tradeoff that shapes how we design data structures and optimize algorithm performance.

Interactive Memory Hierarchy

CPU Registers

Ultra-fast storage directly in the processor core

1 cycle

64-1024 bytes

L1 Cache

First level cache split into instruction and data caches

3-4 cycles

32-128 KB

L2 Cache

Unified cache shared between instruction and data

10-12 cycles

256KB - 2MB

L3 Cache

Last level cache shared across all CPU cores

30-40 cycles

8-64 MB

Main Memory (RAM)

Primary system memory for active programs and data

200-300 cycles

8-128 GB

SSD Storage

Fast non-volatile storage using flash memory

25,000 cycles

256GB - 8TB

Hard Disk (HDD)

High-capacity mechanical storage with spinning platters

10M+ cycles

500GB - 20TB

CPU Registers

Access Speed

1 cycle

Typical Size

64-1024 bytes

Cost per GB

Extremely High

Location

Inside CPU

Characteristics

Fastest possible access speed
Extremely limited capacity
Directly accessed by CPU instructions
No cache miss penalty

Primary Usage

Store currently executing instruction operands
Hold intermediate calculation results
Function call stack management
Loop counters and temporary variables

Real Examples

• x86-64: RAX, RBX, RCX, RDX registers
• ARM: R0-R15 general purpose registers
• RISC-V: x0-x31 integer registers

Speed Comparison

If accessing a CPU register took 1 second, here's how long other memory accesses would take:

CPU Register

1 second

L1 Cache

3 seconds

L2 Cache

10 seconds

L3 Cache

30 seconds

Main Memory

3-5 minutes

SSD Storage

7 hours

Hard Drive

4+ months

Cache Behavior Impact

Sequential Access (Cache-Friendly)

for (i = 0; i < 1000000; i++) {

array[i] = array[i] + 1;

}

Cache hits:~99%

Performance:Excellent

Why:Predictable access pattern

Random Access (Cache-Unfriendly)

for (i = 0; i < 1000000; i++) {

idx = random() % size;

array[idx] = array[idx] + 1;

}

Cache hits:~10%

Performance:Poor

Why:Unpredictable access pattern

Key Insights for Data Structures

Arrays: Excellent cache performance due to contiguous memory layout
Linked Lists: Poor cache performance due to scattered memory locations
Hash Tables: Mixed performance depending on collision handling
Trees: Moderate performance, better with locality-aware implementations

Back to Module 1 Next: Data Structures Overview

Interactive Memory Hierarchy

CPU Registers

Ultra-fast storage directly in the processor core

1 cycle

64-1024 bytes

L1 Cache

First level cache split into instruction and data caches

3-4 cycles

32-128 KB

L2 Cache

Unified cache shared between instruction and data

10-12 cycles

256KB - 2MB

L3 Cache

Last level cache shared across all CPU cores

30-40 cycles

8-64 MB

Main Memory (RAM)

Primary system memory for active programs and data

200-300 cycles

8-128 GB

SSD Storage

Fast non-volatile storage using flash memory

25,000 cycles

256GB - 8TB

Hard Disk (HDD)

High-capacity mechanical storage with spinning platters

10M+ cycles

500GB - 20TB

CPU Registers

Access Speed

1 cycle

Typical Size

64-1024 bytes

Cost per GB

Extremely High

Location

Inside CPU

Characteristics

Fastest possible access speed
Extremely limited capacity
Directly accessed by CPU instructions
No cache miss penalty

Primary Usage

Store currently executing instruction operands
Hold intermediate calculation results
Function call stack management
Loop counters and temporary variables

Real Examples

• x86-64: RAX, RBX, RCX, RDX registers
• ARM: R0-R15 general purpose registers
• RISC-V: x0-x31 integer registers

Cache Behavior Impact

Sequential Access (Cache-Friendly)

for (i = 0; i < 1000000; i++) {

array[i] = array[i] + 1;

}

Cache hits:~99%

Performance:Excellent

Why:Predictable access pattern

Random Access (Cache-Unfriendly)

for (i = 0; i < 1000000; i++) {

idx = random() % size;

array[idx] = array[idx] + 1;

}

Cache hits:~10%

Performance:Poor

Why:Unpredictable access pattern

Key Insights for Data Structures

Arrays: Excellent cache performance due to contiguous memory layout
Linked Lists: Poor cache performance due to scattered memory locations
Hash Tables: Mixed performance depending on collision handling
Trees: Moderate performance, better with locality-aware implementations