Motivation of Fuel's word size

General
1

What is the main motivation for Fuel choosing a word size of 64 bits instead of usual 256 bits?
This is hardening portability of existing Solidity libraries.

2

Hi @onlyforweb3 ,

The 64-bit word size is based around modern virtual machine and ISA standards.

Outside of the blockchain world 32 and 64 -bit systems are the norm, not the exception.

256-bit words were only something that came from the EVM and cause a significant amount of execution overhead with little benefit to the developer.

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3

Totally agreeing about outside blockchain world.
Inside crypto space which remains until now small anyways, i’m afraid several EVM devs will find difficulties trying/migrating to FuelVM architecture due to these fundamental differences.

4

The 256-bit word side really should not affect how a Solidity developer uses the system though.

The FuelVM has arithmetic operations for U128 and U256 numbers:

The Sway language provides first-class support for b256 as a primitive type and U128 / U256 numbers.

Some examples in Sway:

I’d also recommend trying out the Solidity → Sway Transpiler (Charcoal), just open the Sway Playground and click Solidity, then select an example to transpile. This should help show you what’s available for Sway in terms of functionality.

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5

It also should be noted that the EVM is generally the exception, even in the blockchain world:

  • Solana’s SVM: 64-bits
  • Move (Sui/Aptos): 64-bits
  • Cosmos SDK: 64-bits
  • WASM (CosmWasm, NEAR, Arbitrum Stylus, Fluent): 32-bits
  • StarkNet/Cairo: 251-bits :melting_face:
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6

Interesting discussion, thanks for your replies!

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