InternetOfPeers / test-gas-costs

This repo is a support for answers to several questions posted on StackExchange

Test gas costs

This repo is a support for the answers to the following questions posted on StackExchange:

• What is the most gas efficient way to get the value of a bit in an unsigned integer?
• What are the pros and cons of emitting events vs return statements?
• Using assembly to store more values per word

And to the tweet:

• seems like ++i is about 5 gas cheaper per loop—guessing this is because a temporary variable doesn't have to be created to return the value of i prior to incrementing when it's ++i?

Please don't take it as an example of good programming, it is just a very raw and fast way to test gas costs ;)

Start a local geth node in dev mode with

geth --http --dev

Then run

truffle compile
truffle test

Output will be something like this

Using network 'development'.

Compiling your contracts...
===========================
> Everything is up to date, there is nothing to compile.

  Contract: TestEvents
testReturnData 4235
    ✓ check costs 1
testReturnAndUseData 4247
    ✓ check costs 2
testEmitData 5681
    ✓ check costs 3

  Contract: TestGasCosts
test1 188 188 188 188
    ✓ check costs 1 (1026ms)
test2 142 142 142 142
    ✓ check costs 2
test3 93 103 103 103
    ✓ check costs 3
test4 7 7 7 24
    ✓ check costs 4
test5 188 188 188 188
    ✓ check costs 5

  Contract: TestLoops
testPlusPlusI 43068
    ✓ check costs 1
testIPlusPlus 43068
    ✓ check costs 2

  Contract: TestPackingUint16
setPackedUint16 28901
    ✓ check costs 1 (1016ms)
testSetUint16 88443
    ✓ check costs 2
testPack 22134
    ✓ check costs 3


  13 passing (4s)