Gas Optimization

Storage Efficiency

Storage Layout

Delegate Call Detection

Low-Level Calls

Memory Manipulation

By taking full control of the data and execution flow, you can optimize your contracts a step further. Inline assembly allows you to employ EVM instructions in unorthodox ways, so long as you make the proper assumptions about your data.

In the <code class="richtext rt-inlinecode">contracts/</code> folder, you will find both a reference implementation and a challenge.

They both should implement a simple function copying a <code class="richtext rt-inlinecode">bytes memory array</code>, can you use assembly to optimize the function in <code class="richtext rt-inlinecode">Challenge.sol</code> and achieve gas efficiency?

lightBulb

Like before, code will be compiled and evaluated using <b>800</b> optimization runs.

Implement <code class="richtext rt-inlinecode">copyArray(bytes)</code> in <code class="richtext rt-inlinecode">contracts/Challenge.sol</code> in the most gas efficient way you can come up with!

Optimization Challenge

You see Luc’s mistake, but before you can speak, his mead explodes in a cloud of icy vapor. Shards of ice burst up into the rafters and float down onto the heads of the tavern’s patrons. 

Luc looks over at you, his jaw agape, and shortly he bursts into laughter. His amusement at his own folly spreads to you, and soon the rest of the tavern. As you laugh, you glance down to see a perfect sphere of ice hovering above your tankard. The others slap you on the shoulders, congratulating you on your second victory. 

I guess I hadn’t perfected my spell as much as I thought, well done guardian!

Your new friends shake your hand, and a round of fresh drinks is ordered. You spend the rest of the night laughing and swapping stories with this group of newfound companions. You cannot wait to see what other adventures await you in the world of Spell Tuning.

The mages around the table settle back, ready to hear the next challenge. 

Warm mead is no fun! For the next round let’s see who can freeze their mead into a block of ice first!

Everyone leans over their mugs, concentrating on their spells. You concentrate, clear your mind and cast your ice spell. Slowly your mead begins to form into a ball of ice. 

But your eye is caught by what Luc is doing across from you… 

In this quest, we have seen how inline assembly can achieve aggressive optimization and help drastically lower gas consumption.

Batching operations is a recurring strategy in programming. Similar to how it can help lower the execution time in traditional contexts, it can be used to reduce gas consumption in Solidity.

The use of inline assembly gives you reins to the EVM's memory. However, be aware that you outside the assembly block, Solidity still expects its <a class="richtext rt-link" target="_blank" rel="noopener noreferrer" href="https://docs.soliditylang.org/en/latest/assembly.html#memory-safety">memory model</a> to be maintained. It is hence, your responsibility to make sure your assembly code respects this model.

In some specific cases, assembly, and its full control over memory, is the most efficient way to optimize a snippet of code.

Practice using inline assembly in your Solidity smart contracts to further optimize them, to an extent vanilla Solidity does not offer!

Assembly Optimization

prelude