Execution model
So far, we’ve learned about the series of steps that have to happen for a transaction to execute from start to finish. Now, we’ll look at how the transaction actually executes within the VM.
The part of the protocol that actually handles processing the transactions is Ethereum’s own virtual machine, known as the Ethereum Virtual Machine (EVM).
The EVM is a Turing complete virtual machine, as defined earlier. The only limitation the EVM has that a typical Turing complete machine does not is that the EVM is intrinsically bound by gas. Thus, the total amount of computation that can be done is intrinsically limited by the amount of gas provided.
Image for post
Source: CMU
Moreover, the EVM has a stack-based architecture. A stack machine is a computer that uses a last-in, first-out stack to hold temporary values.
The size of each stack item in the EVM is 256-bit, and the stack has a maximum size of 1024.
The EVM has memory, where items are stored as word-addressed byte arrays. Memory is volatile, meaning it is not permanent.
The EVM also has storage. Unlike memory, storage is non-volatile and is maintained as part of the system state. The EVM stores program code separately, in a virtual ROM that can only be accessed via special instructions. In this way, the EVM differs from the typical von Neumann architecture, in which program code is stored in memory or storage.
Image for post
The EVM also has its own language: “EVM bytecode.” When a programmer like you or me writes smart contracts that operate on Ethereum, we typically write code in a higher-level language such as Solidity. We can then compile that down to EVM bytecode that the EVM can understand.
Okay, now on to execution.
Before executing a particular computation, the processor makes sure that the following information is available and valid:
System state
Remaining gas for computation
Address of the account that owns the code that is executing
Address of the sender of the transaction that originated this execution
Address of the account that caused the code to execute (could be different from the original sender)
Gas price of the transaction that originated this execution
Input data for this execution
Value (in Wei) passed to this account as part of the current execution
Machine code to be executed
Block header of the current block
Depth of the present message call or contract creation stack
At the start of execution, memory and stack are empty and the program counter is zero.
PC: 0 STACK: [] MEM: [], STORAGE: {}
The EVM then executes the transaction recursively, computing the system state and the machine state for each loop. The system state is simply Ethereum’s global state. The machine state is comprised of:
gas available
program counter
memory contents
active number of words in memory
stack contents.
Stack items are added or removed from the leftmost portion of the series.
On each cycle, the appropriate gas amount is reduced from the remaining gas, and the program counter increments.
At the end of each loop, there are three possibilities:
The machine reaches an exceptional state (e.g. insufficient gas, invalid instructions, insufficient stack items, stack items would overflow above 1024, invalid JUMP/JUMPI destination, etc.) and so must be halted, with any changes discarded
The sequence continues to process into the next loop
The machine reaches a controlled halt (the end of the execution process)
Assuming the execution doesn’t hit an exceptional state and reaches a “controlled” or normal halt, the machine generates the resultant state, the remaining gas after this execution, the accrued substate, and the resultant output.
Phew. We got through one of the most complex parts of Ethereum. Even if you didn’t fully comprehend this part, that’s okay. You don’t really need to understand the nitty gritty execution details unless you’re working at a very deep level.
How a block gets finalized
Finally, let’s look at how a block of many transactions gets finalized.
When we say “finalized,” it can mean two different things, depending on whether the block is new or existing. If it’s a new block, we’re referring to the process required for mining this block. If it’s an existing block, then we’re talking about the process of validating the block. In either case, there are four requirements for a block to be “finalized”:
1) Validate (or, if mining, determine) ommers
Each ommer block within the block header must be a valid header and be within the sixth generation of the present block.
2) Validate (or, if mining, determine) transactions
The gasUsed number on the block must be equal to the cumulative gas used by the transactions listed in the block. (Recall that when executing a transaction, we keep track of the block gas counter, which keeps track of the total gas used by all transactions in the block).
3) Apply rewards (only if mining)
The beneficiary address is awarded 5 Ether for mining the block. (Under Ethereum proposal EIP-649, this reward of 5 ETH will soon be reduced to 3 ETH). Additionally, for each ommer, the current block’s beneficiary is awarded an additional 1/32 of the current block reward. Lastly, the beneficiary of the ommer block(s) also gets awarded a certain amount (there’s a special formula for how this is calculated).
4) Verify (or, if mining, compute a valid) state and nonce
Ensure that all transactions and resultant state changes are applied, and then define the new block as the state after the block reward has been applied to the final transaction’s resultant state. Verification occurs by checking this final state against the state trie stored in the header.
bitcoin maps bitcoin купить bitcoin litecoin monero fork bitcoin код майнить bitcoin bitcoin оплата bitcoin rpg second bitcoin bitcoin доходность bitcoin center maps bitcoin bitcoin miner bitcoin выиграть freeman bitcoin bitcoin программирование продам bitcoin lamborghini bitcoin bitcoin биткоин bitcoin scam polkadot su биржа ethereum bitcoin china
bitcoin хешрейт
programming bitcoin вывод ethereum bitcoin x2 ethereum форк bitcoin alien bitcoin advertising bitcoin фирмы bitcoin png trezor bitcoin клиент ethereum
ethereum russia bistler bitcoin monero биржи
bitcoin уязвимости bitcoin carding bitcoin вклады wallet cryptocurrency калькулятор bitcoin оборот bitcoin bitcoin добыть bitcoin монеты
краны monero
bitcoin alert sberbank bitcoin bitcoin example bitcoin eth bitcoin buying 'Block' refers to the fact that data and state is stored in sequential batches or 'blocks'. If you send ETH to someone else, the transaction data needs to be added to a block for it to be successful.Establish digital identityпокер bitcoin bitcoin wm
bitcoin alliance blocks bitcoin all bitcoin bitcoin игры bitcoin trojan cryptocurrency это bitcoin alliance прогноз ethereum bitcoin монета bitcoin настройка платформа bitcoin amd bitcoin Because you choose your assignment and you solve your own problems, you have nobody to blame but yourself if something doesn’t work.torrent bitcoin wallets cryptocurrency bitcoin bloomberg casper ethereum bitcoin keys
bitcoin server nem cryptocurrency мастернода bitcoin майнинг bitcoin книга bitcoin обвал bitcoin bitcoin okpay js bitcoin bitcoin landing халява bitcoin
bitcoin reindex создатель ethereum bitcoin aliexpress bitcoin work
bitcoin обзор pps bitcoin
bitcoin shops порт bitcoin bitcoin wordpress bitcoin spend bitcoin заработать bitcoin рулетка bitcoin баланс jax bitcoin forex bitcoin
click bitcoin bitcoin china bitcoin бесплатно bitcoin программирование clame bitcoin monero client bitcoin png bitcoin multiplier bitcoin продать finney ethereum bitrix bitcoin bitcoin cny bitcoin electrum ubuntu ethereum bitcoin покер ethereum habrahabr platinum bitcoin space bitcoin amazon bitcoin bitcoin betting компания bitcoin mine ethereum рубли bitcoin buy tether краны ethereum monero btc
takara bitcoin
bitcoin price
bitcoin кэш bitcoin goldmine
primedice bitcoin ethereum core bitcoin payeer bitcoin neteller взлом bitcoin bitcoin okpay
love bitcoin bitcoin knots x bitcoin
bitcoin org The Disadvantages of Investing in ETH Short-Term:ethereum курсы byzantium ethereum биржа ethereum зарегистрироваться bitcoin аналоги bitcoin bitcoin github bitcoin symbol metal bitcoin bitcoin xyz
hd7850 monero форум bitcoin
bitcoin strategy
bitcoin png
bitcoin miner bitcoin прогноз difficulty bitcoin bitcoin prune
bitcoin earn arbitrage cryptocurrency ethereum course 2016 bitcoin bitcoin freebitcoin bitcoin ios bitcoin окупаемость monero обменник hd bitcoin bitcoin сатоши Another tool many people like to buy is a Bitcoin debit card which enables people to load a debit card with funds via bitcoins.According to Mark T. Williams, as of 30 September 2014, bitcoin has volatility seven times greater than gold, eight times greater than the S%trump2%P 500, and 18 times greater than the US dollar. Hodl is a meme created in reference to holding (as opposed to selling) during periods of volatility.bitcoin ann bitcoin казино webmoney bitcoin bitcoin магазины проекта ethereum bitcoin мошенничество zcash bitcoin panda bitcoin ethereum майнить market bitcoin download bitcoin bitcoin gif purchase bitcoin картинка bitcoin bitcoin node bitcoin png bitcoin paper daily bitcoin wallets cryptocurrency ethereum cpu bitcoin metal buy ethereum bitcoin обменники bitcoin books bitcoin регистрация forex bitcoin production cryptocurrency ethereum txid metal bitcoin email bitcoin dat bitcoin ethereum кошельки ethereum телеграмм topfan bitcoin cryptocurrency forum 22 bitcoin tether верификация bitcoin андроид bitcoin информация usb tether bitcoin life
wikipedia cryptocurrency cz bitcoin uk bitcoin
добыча bitcoin ethereum эфириум
bitcoin кэш bitcoin land bitcoin grafik
bitcoin конференция стратегия bitcoin invest bitcoin bitcoin icons bitcoin вирус monero форум monero калькулятор bitcoin gif bitcoin игры новости bitcoin qtminer ethereum обмен bitcoin
лотерея bitcoin алгоритмы bitcoin bitcoin space bitcoin paypal bitcoin fund bitcoin qiwi казино ethereum trezor bitcoin bitcoin биржа ethereum project 0 bitcoin bitcoin вклады верификация tether monero client bitcoin explorer разделение ethereum яндекс bitcoin all cryptocurrency bitcoin автокран
by bitcoin monero difficulty bitcoin group яндекс bitcoin forum cryptocurrency бесплатные bitcoin
bitcoin зебра bitcoin окупаемость converter bitcoin space bitcoin bitcoin free оплатить bitcoin bitcoin автомат tether usdt bitcoin change solo bitcoin ethereum продам bitcoin adress market bitcoin moto bitcoin bitcoin jp bitcoin адреса avto bitcoin home bitcoin blacktrail bitcoin bitcoin сборщик ethereum упал aml bitcoin
bitcoin реклама отзывы ethereum блокчейна ethereum
000009ff7ff1fc53b92dc18148a1d65dfc2d4b1fa3d677284addd200126d9069таблица bitcoin bitcoin q bitcoin p2p nicehash monero bitcoin видеокарта attack bitcoin
Bitcoin logopanda bitcoin bitcoin cryptocurrency water bitcoin
bitcoin de ethereum programming ethereum адрес bitcoin prices cryptocurrency tech bitcoin kraken bitcoin коллектор poloniex ethereum service bitcoin bitcoin 2017 dwarfpool monero bitcoin торговля bitcoin wallpaper bitcoin registration bitcoin poker bitcoin banks ethereum linux удвоитель bitcoin amazon bitcoin значок bitcoin
fx bitcoin bitcoin сша short bitcoin That’s why miners 'pool' together their computational power into 'mining pools,' to improve their chances of solving the cryptographic puzzles and earning ether. Then, they split the profits proportional to how much power each miner contributed.4. It’s Not Feasible (Or It’s Prohibited) In Your Geographic LocationThe authenticity of a transaction is verified and confirmed by participantsbitcoin hardfork collector bitcoin bitcoin лотереи биржи monero collector bitcoin аналоги bitcoin карты bitcoin bitcoin книга
tether wallet transaction bitcoin 33 bitcoin ethereum видеокарты ropsten ethereum генераторы bitcoin ethereum stratum ann ethereum bitcoin skrill bitcoin вконтакте cryptocurrency trading bitcoin отзывы обменник tether серфинг bitcoin currency bitcoin One example is to use this approach to create a decentralized social network that’s resistant to censorship. Most mainstream social apps, such as Twitter, censor some posts, and some critics argue those social apps apply inconsistent standards about what content is censored or 'downranked.'On 4 December 2013, Alan Greenspan referred to it as a 'bubble' as did George Soros on 25 January 2018. Warren Buffett called bitcoin a 'mirage' on 13 March 2014.mixer bitcoin bitcoin установка сайты bitcoin rush bitcoin bitcoin ферма
hack bitcoin bitcoin server bitcoin goldman reddit ethereum solo bitcoin bitcoin stock bitcoin cards super bitcoin sberbank bitcoin simple bitcoin mine ethereum bitcoin биткоин bitcoin webmoney ledger bitcoin bitcoin agario mooning bitcoin topfan bitcoin bye bitcoin bitcoin store mercado bitcoin earn bitcoin bitcoin avalon bitcoin пополнение ethereum claymore bitcoin phoenix приложение tether bitcoin софт carding bitcoin nicehash bitcoin bitcoin сколько monero nvidia bitcoin трейдинг bitcoin anonymous bitcoin математика ethereum coins bitcoin game
ферма ethereum новости bitcoin робот bitcoin
statistics bitcoin
system bitcoin bitcoin conf проект bitcoin bitcoin machine форумы bitcoin bitcoin конвертер bitcoin казино bitcoin алгоритм ethereum habrahabr tracker bitcoin bitcoin значок visa bitcoin github ethereum доходность ethereum андроид bitcoin shot bitcoin bitcoin софт bitcoin отзывы
bitcoin ru bitcoin cloud cryptocurrency dash nodes bitcoin bitcoin trading cryptocurrency charts fpga bitcoin freeman bitcoin эфир ethereum bitcoin golden app bitcoin android tether bitcoin free arbitrage cryptocurrency Bitcoin mining is a highly competitive, dynamic, almost perfect market. Mining rigs can be set up and dismantled almost anywhere in the world with relative ease. Thus, market forces are constantly pushing mining activity to places and times where the marginal price of electricity is low or zero. These electricity products are cheap for a reason. Often, it’s because the electricity is difficult (and wasteful) to transport, difficult to store, or because there is low demand and high supply. Using electricity in this way is a lot less wasteful than simply plugging a mining rig into the mains indiscriminately.bitcoin бумажник For open, public blockchains, this involves mining. Mining is built off a unique approach to an ancient question of economics — the tragedy of the commons.bitcoin rbc bitcoin market перспективы bitcoin bitcoin мошенники bitcoin get And if you understand the deep and central role that money plays in every aspect of our lives, then might Bitcoin not be as important as the printing press, the automobile, and the internet. In fact, not everyone is literate, not everyone has a car, and not everyone is online, but everyone uses money. (And for those who are wondering, you do not need internet access to use Bitcoin.)Latest Coinbase Coupon Found:акции bitcoin ethereum 2017 bitcoin стратегия txid ethereum hosting bitcoin
bitcoin хардфорк взлом bitcoin carding bitcoin
bitcoin серфинг bitcoin майнить ethereum википедия cryptocurrency gold
boxbit bitcoin Miningbitcoin monkey ethereum coingecko bitcoin now брокеры bitcoin ethereum info reddit cryptocurrency ethereum сайт monero криптовалюта дешевеет bitcoin работа bitcoin ethereum russia добыча bitcoin bitcoin stock flash bitcoin ethereum flypool
ethereum видеокарты bitcoin joker goldmine bitcoin
bitcoin check bitcoin hacker автомат bitcoin bitcoin гарант tether скачать wifi tether bitcoin dice
bitcoin инвестиции прогноз bitcoin bitcoin android bitcoin лохотрон microsoft ethereum
swarm ethereum bitcoin protocol пул monero bitcoin sec boom bitcoin bitcoin tools bitcoin bear bitcoin coinmarketcap торги bitcoin transactions bitcoin bitcoin word
dat bitcoin bitcoin приложение bitcoin иконка bitcoin world программа tether bitcoin puzzle обмен tether bitcoin x2 double bitcoin