Struct Field Alignment and Memory Optimization

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Problem Statement

At a high-frequency trading firm, every byte matters. A poorly aligned struct wastes 40% memory. Explain struct alignment and optimize a given struct layout.

The Problem: Padding Waste

Alignment Rules

Type	Size	Alignment
bool, int8, uint8	1 byte	1 byte
int16, uint16	2 bytes	2 bytes
int32, uint32, float32	4 bytes	4 bytes
int64, uint64, float64, pointer	8 bytes	8 bytes

Use fieldalignment Tool

Practical Exercise

When It Matters

Millions of structs in memory (caches, databases)
CPU cache efficiency (cache line = 64 bytes)
Network protocols with fixed layouts

// BAD: 24 bytes due to padding
type BadStruct struct {
    a bool    // 1 byte + 7 padding
    b int64   // 8 bytes
    c bool    // 1 byte + 7 padding
}

// GOOD: 16 bytes (reordered)
type GoodStruct struct {
    b int64   // 8 bytes
    a bool    // 1 byte
    c bool    // 1 byte + 6 padding
}

// Optimize this struct:
type User struct {
    IsActive   bool      // 1
    Age        int32     // 4
    ID         int64     // 8
    IsVerified bool      // 1
    Score      float64   // 8
    Flags      uint8     // 1
}

// Before: 40 bytes
// After optimization: 32 bytes
type UserOptimized struct {
    ID         int64     // 8
    Score      float64   // 8
    Age        int32     // 4
    IsActive   bool      // 1
    IsVerified bool      // 1
    Flags      uint8     // 1 + 1 padding
}