Solidity: Document costs of various types.

[mudgen]

Does it cost any gas to cast a bytes32 memory value to uint256? What is the assembly op code for this?

Does it cost more gas to use =, >, <. operators with bytes32 than it does with uint256?

Spreadsheets about gas costs say it cost 3 gas for =, >, < operations, so is that true with all types that support those operators? Or is the gas cost for these operators different depending on the type?

I tested some of these things in remix and got mixed results -- sometimes it cost more gas, sometimes less.

Does it make any sense to cast bytes32 to unint256 for doing an operation like this: require(uint256(myvalue) != 0);

If you know the answers to these, can you please tell me how you know?

[chriseth]

In general, bytes32 and uint256 are mostly equivalent with regards to gas and I'm actually surprised you got different results. Did you change the function signature somewhere?

[mudgen]

Yes, my two test functions have different names.

[mudgen]

From my investigation it seems that there is a gas cost to cast a value if the cast changes the size of the value.

For instance casting bytes32 to uint256 does not cost gas because they are the same size. I wish there were a list of rules about these things somewhere that was easy to read.

Using an operator such as =,>,< will cost more gas if a cast needs to happen for the operation to occur and the cast causes one of the arguments to change size.

[chriseth]

Yes, some guidelines about the costs of various types should be added to the documentation.

[gitcoinbot]

Issue Status: 1. Open 2. Started 3. Submitted 4. Done

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[itsN1X]

@chriseth , I had to have a few things debriefed:
Like,

• [ ] : Type of format for /docs
  e.g., Jekyll, Pandoc, rtm, PDF, html, etc.
• [ ] : Level of detailing:
  e.g.: I'm planning on covering all opcodes, with child --heads on each /dataType.
  Also, what all are the checkboxes I must tick?

My basic reference is the spresdsheet .1 from the wikipedia footnotes on its eth page.
i.e. .30, .32, and the one tagged in this issue.

Anything , or everything else you'd want me to know?
Any better citations, sources?
Also, my /ETA for the v0.0.1 draft shall be 100,000secs, from now.

cc/ @vs77bb
tysm!
~N1X

[chriseth]

@itsN1X this was more meant to be a high level description of the tradeoffs of different types with respect to gas, and not a detailed table with costs per opcode (although that could also be beneficial), since users usually do not know how they code is translated into opcodes (and I guess this is also where most confusion with regards to gas comes from).

[chriseth]

Oh and please don't use the spreadsheet but for example an implementation of a compliant client or the yellowpaper.

[gitcoinbot]

@itsN1X Hello from Gitcoin Core - are you still working on this issue? Please submit a WIP PR or comment back within the next 3 days or you will be removed from this ticket and it will be returned to an ‘Open’ status. Please let us know if you have questions!

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[itsN1X]

@gitcoinbot Yep, still here! W-I-P.

[gitcoinbot]

@itsN1X. :wave: thanks for the atMention, but you need to install @gitcoinbot on this repo for me to be able to respond. More details in the documentation.

:v:
@gitcoinbot

[gitcoinbot]

@itsN1X Hello from Gitcoin Core - are you still working on this issue? Please submit a WIP PR or comment back within the next 3 days or you will be removed from this ticket and it will be returned to an ‘Open’ status. Please let us know if you have questions!

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[gitcoinbot]

Issue Status: 1. Open 2. Started 3. Submitted 4. Done

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[vs77bb]

Hi @itsN1X, would you mind linking to the WIP PR so we know where this issue is?

[itsN1X]

I have a small wiki I made for self reference that I plan to convert to a online manual. Would require another week to get everything finished.

[gitcoinbot]

@itsN1X Hello from Gitcoin Core - are you still working on this issue? Please submit a WIP PR or comment back within the next 3 days or you will be removed from this ticket and it will be returned to an ‘Open’ status. Please let us know if you have questions!

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Issue Status: 1. Open 2. Started 3. Submitted 4. Done

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@itsN1X due to inactivity, we have escalated this issue to Gitcoin's moderation team. Let us know if you believe this has been done in error!

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[vs77bb]

Hi @itsN1X do you have any update here? If not, we'll plan to send this back out to 'Open' status. Hope you're doing well!

[itsN1X]

I'm really sorry for being shoddy in my communications, my bad!
Personally, examinationseason at the University has been taxing much.
I humbly request the Funders to allow me a deadline till 2.7, after which the issue may be re-opened.
Prepared a wireframe for this, hope to get a working prototype soon.
tysm for all the patience,
I apologize for the uncontrollable delays.

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[itsN1X]

I'll upload.

Yes, expire me at 07-07-2018 iff I don't pull-in.

@14BME0133

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[gitcoinbot]

Issue Status: 1. Open 2. Cancelled

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[itsN1X]

Yes, some guidelines about the costs of various types should be added to the documentation.

Possibly this should be moved to a new issue.

"bounty" label should be removed

$I need someone to co-do-it ... Please feel free to drop by to team up ( :

[ChrisChinchilla]

@itsN1X I'm happy to help you with this, I am working with the Solidity team on docs, so don't need any GitCoin contributions, but more to help you with submitting a PR, reviewing etc. Let me know if you need anything.