# FAQ

- Q: What is grin?  A: An implementation of [MimbleWimble](https://download.wpsoftware.net/bitcoin/wizardry/mimblewimble.txt)
- Q: Similar to Bitcoin?  A: Both are outputs-based, PoW. See also [Grin for Bitcoiners](grin4bitcoiners.md)
- Q: Mining? A: Testnet only. CPU, synchronous. GPU or asynchronous is not yet supported.
- Q: Block height? A: HTTP GET /v1/chain on a public peer node, for example http://testnet1.yeastplume.com:13413/v1/chain or (grintest.net)[https://grintest.net/]
- Q: Store of value? A: Not yet. Wait for Mainnet. Testnet1 can still disappear and reappear unexpectedly.
- Q: Block size limit? Target mean block time?  A: Target mean block time is 1 block per 60 seconds. The size is limited by transaction "weight", though there is also a hard cap on the order of tens of MB.
- Q: Does grin scale?  A: Yes, it might eventually do, thanks to transaction cut-through and possible level 2 solutions.
- Q: Fees? Monetary policy? A: https://github.com/mimblewimble/grin/wiki/fees-mining
- Q: Roadmap? A: Moving fast, changing things. Maybe look at [issues and milestones](https://github.com/mimblewimble/grin/milestones)
- Q: Proof of payment? A: Planned. Maybe in Testnet2
- Q: Microtransactions? A: On Testnet1, fees are 0.8% on a transaction of 1.0 coins.
- Q: Could grin ever support or make use of:
  ☑ Probably, or ☐ Probably not
  A: ☑ Contracts, ☑ [Pruning](pruning.md), ☐ Identity, like bitauth, ☑ SNARKs, [☑ Cross chain atomic swaps, ☑ multisig, ☑ time locks, ☑ lightning network](grin4bitcoiners.md#scripting), ☑ Payment channels, ☑ hidden nodes / onion routing, ☑ [Scripting - clean & native w/ tiny limits](https://lists.launchpad.net/mimblewimble/msg00029.html)
- Q: HW requirements for mining? A: Not much. Don't invest in equipment yet, there's not even a final beta released, and a lot can change before any official blockchain is launched.
- Q: Quantum safe?  A: No. Given sufficient warning, some QC resistance can be introduced through softforks.

# Troubleshooting

## Coins are 'confirmed but still locked'?
Like other cryptocurrencies, newly mined coins are time locked, so mined coins can't be spent immediately.

## "Peer request error" or other peer/network issues after restarting grin server
Possible workaround is `rm -rf .grin/peers/*`  then restart.

## grin server or waller crashes or hangs
Yes, this still happens quite often. You'll need to babysit grin.
Very welcome any solutions to give grin a "watchdog" solution that can restart
grin in case of trouble.

## Build error: Could not compile `tokio-retry`.
You might want to remove any previous rust installations to avoid conflicts.
Use `rustup` to [reinstall rust and cargo as described](build.md).

NOTE: If you install rust or cargo with your package manager (most Linuxes
anno 2017) you'll get too old versions. On Debian, you might have to manually
compile cmake or get it from non-default repositories.

## Build error: `failed to select a version for 'serde_json'`
Run `cargo update` to fix this

## Build error: Panic during rocksdb compilation.
This is caused by missing Linux headers. Install the development headers with
your favorite package manager (usually they are called `linux-headers`).

# Short term plans
## Transaction types
- (DONE) A temporary simple transaction exchange. Temporary - will be deprecated.
- (months) Maybe in testnet2 Full transaction; an exchange which involves a full roundtrip between sender and receiver using aggregate (Schnorr) signatures. Usable as proof of payment and for multisig.