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I have trouble deploying a contract to the main network and I believe this is due to high gas consumption. An earlier version of the contract worked on the main network. The current version works in my private testnet (created with geth --dev). On the testnet these contract creations use about 2.4 million units of gas. I tried to deploy it on the main net with 2 million gas at first and got an out of gas exception (TA got mined though, contract creation just was not successful).

After that I tried it with 3 million and got this (not mined):

"{"jsonrpc":"2.0","error":{"code":-32010,"message":"Transaction cost exceeds current gas limit. Limit: 2200000, got: 3000000. Try decreasing supplied gas.","data":null},"id":1}[\n]"

I am completely stuck and have no idea how I can deploy my contract now. Mainly I have two questions:

  1. Why can I send a TA with 2.4 million gas to the testnet but not to the main-net. I know they are different chains, but shouldn't it use the same logic for TA-validation? How can I send TAs with 3mill gas limit to the main network?
  2. I don't understand why my contract requires this much gas. It's only 264 lines of code. It's three mappings, two structs, five enums, one event and a few relatively simple functions. How can I figure out which part of my contract is using up so much gas? Is there a tool for that?
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The reason why geth refuses to send the transaction is because the block gas limit varies. On a private testnet, it can be anything, but by default it'll be 5.5 million. On the mainnet, it's currently only 2 million--so a 3 million gas transaction just wouldn't fit at all. This is because of the recent spam attacks on the network--the developers asked miners to reduce the limit, and they did. Hopefully, the miners will increase it back to the default after the incoming hardfork. (I say "hopefully" because it's the miners' decision, the devs can only suggest.)

The only things that use gas at creation time are what happens in the constructor, and the size of the compiled code itself. You might be able to reduce the size by turning on the optimizer, but it's quite possible it's already on.

I'm not that surprised at the figure it's giving, though. 264 LoC is actually a lot in Ethereum. I have a 400~ LoC contract that is 3~ million gas optimized.

There's three ways of reducing gas cost:

  1. Simplify the contract. This might be impossible, depending on what exactly you're doing.
  2. Split it into multiple contracts.
  3. Refactor it to use libraries. If you're using lots of structs and mappings, this may make your code remarkably more readable.

The simplest way may be just to wait. You're not the only one who is stuck with big contracts, so the miners have an incentive to raise the gas limit again, and soon.

  • ok, that really makes things a lot clearer. How did you get your 3mill-contract deployed? I previously tried splitting into multiple contracts, but had some issues with it and decided to leave it as its only a protoype atm. I simplified my contract down to around 2,05mill gas and send it with a 2.15mill limit. But when I look on etherscan all blocks have a limit of 2mill. Does my TA even have a chance to get mined in the next like 24h or do I need absolutely need to go below 2mill? – Max Binnewies Nov 20 '16 at 22:31
  • I've actually never deployed said giant contract on the mainnet, but I did split a large portion of it into a library. In, re: gas limit it's unlikely to get better within 24h, particularly when the next hardfork is imminent. I suspect (but have no guarantee) that a few days from now the miners will start raising their gas limit target. – Matthew Schmidt Nov 20 '16 at 23:40
  • I actually cut my contract down to the bare minimum(since its only a prototype) to about 200 LoCs. In the testnet it deployd with around 1,995 million gas. I used that bytecode from that deploy and still got an out of gas exception! :-( I guess I have to try something else. The longer I work on this, the longer I think it will take for Ethereum to be ready for the actual market, right now I am guessing ten years. – Max Binnewies Nov 21 '16 at 13:05

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