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Branchless & Cache friendly programming

Wed, 09 Sep 2026 10:58:15 +0530

branch prediction and spacial locality deserve a post of their own but I don’t intend to explain “what” they are in details so you can refer the links later to understand about them in details.

Branchless Programming

1. The Boolean Arithmetic Trick

In C++, a boolean expression evaluates to exactly 1 (true) or 0 (false). You can use this to do math without ever writing an if statement.

The branching way (bad for prediction):

Strictly Align Memory Address

Mon, 07 Sep 2026 11:11:55 +0530

Main Idea

This is a very common technique in systems programming and memory allocators. Consider these macros below

#define ALIGN(sizeof(void*))
#define ALIGN_UP_POW2(x, align) (((x) + (align) - 1) & ~((align) - 1))

… further somewhere in program we have a custom allocator (like arena, free-list memory pools, etc.). Let’s just take a simple variable x and see what happens to it.

uint64_t x = ALIGN_UP_POW2(x, ALIGN);

Maybe you’ve seen all this for the first time and

Packing & Unpacking two integers in one

Sat, 29 Aug 2026 09:37:17 +0530

Simple Example

We will look at simple example of

#include <cstdint>
#include <cstdlib>
#include <iostream>

int main() {
 uint16_t first{};
 uint16_t second{};

 std::cout << "enter first and second values of unsigned integers "
 "respectively (max is "
 << UINT16_MAX << ")\n";

 std::cin >> first >> second;

 uint32_t data{};
 data = ((uint16_t)first << 16) | ((uint16_t)second);

 std::cout << "First value is " << (data >> 16) << '\n';
 std::cout << "Second value is " << (data & 0xFFFF) << '\n';

 return EXIT_SUCCESS;
}

Packing

consider this line…

uint32_t data = ((uint16_t)first << 16) | ((uint16_t)second);

To get a big picture of what’s happening, let’s take an example

Intrusive Data Type

Mon, 17 Aug 2026 10:49:05 +0530

What is an Intrusive Data Type?

Embedding “dataless” structures into the data type is called intrusive data structures, because you need to modify your data type to use it. Now that the data structure is free of data, to get the data back, just offset the address of the struct.

A normal linked list of the data would look like this

 ┌──┐ ┌──┐
 │ ▼ │ ▼
┌Node──┐ │ ┌Node──┐ │ ┌Node──┐
│┌────┐│ │ │┌────┐│ │ │┌────┐│
││next├┼─┘ ││next├┼─┘ ││next├┼──▶ …
│├────┤│ │├────┤│ │├────┤│
││ptr ││ ││ptr ││ ││ptr ││
│└─┬──┘│ │└─┬──┘│ │└─┬──┘│
└──┼───┘ └──┼───┘ └──┼───┘
 ▼ ▼ ▼
 ┌────┐ ┌────┐ ┌────┐
 │data│ │data│ │data│
 └────┘ └────┘ └────┘

but an intrusive linked list of all the data would look like

Type Punning

Sun, 09 Aug 2026 21:53:36 +0530

What is Type Punning?

Type punning is a low-level programming technique in C and C++ that subverts the type system to reinterpret the bit representation of an object of one type as a different, incompatible type. This allows developers to access the underlying binary data directly, bypassing standard type-safe conversions, which is commonly used for performance optimization, serialization, deserialization, and hardware interaction.

Look at this simple example

I’ll just explain with the example directly, look at this example