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CRDT literally means Conflict-free Replicated Data Type. Expecting CRDTs to be conflict-free isn't purism, it's simple validation. Git is, inarguably, not a CRD

by kiitos 2y ago

CRDT literally means Conflict-free Replicated Data Type. Expecting CRDTs to be conflict-free isn't purism, it's simple validation. Git is, inarguably, not a CRDT.

yazaddaruvala 2y ago
> CRDT literally means Conflict-free Replicated Data Type. Git could be "conflict-free" with a simple `rand(ours, theirs)`. It would be useless, but technically "conflict-free". Is the addition or removal of that rand function really, pragmatically the difference in the answer to "what is a CRDT?"
- Groxx 2y ago
  Adding extra rules on top of git to try to turn it into a CRDT doesn't make git one, even if you succeed (and rand would not succeed). You can do that with a pencil and paper, but that doesn't make paper a CRDT.
- jakelazaroff 2y ago
  `rand` wouldn’t work because all peers must reach the same state without coordination.
- kiitos 2y ago
  This is definitely not true. Are you open to understanding why this isn't true? If so, I'm happy to help you come to the correct understanding; please ask whatever questions are necessary. Otherwise, then, well, okay!
LAC-Tech 2y ago
There are CDTS that have "multiple versions", which look an awful lot like conflicts to me, ie, the Multi-Value Register in this paper: https://inria.hal.science/inria-00555588/ https://inria.hal.science/inria-00555588/
- kiitos 2y ago
  Multi-value registers are CRDTs for sure. Conflict-free doesn't mean that values can't have concurrent histories (or, as you say, "multiple versions") -- it means that the merge operation always succeeds.
  - LAC-Tech 2y ago
    What's the definition of a conflict, then? Equations welcome.
    - kiitos 2y ago
      Feel free to read up on CRDTs; I'm confident this will answer your question. The short answer is, roughly, that a conflict is a discrepancy in state which cannot be mechanically resolved.
      - LAC-Tech 2y ago
        I've read a few CRDT papers. Perhaps you could name a specific one.

by kiitos 2y ago

CRDT literally means Conflict-free Replicated Data Type. Expecting CRDTs to be conflict-free isn't purism, it's simple validation. Git is, inarguably, not a CRDT.

yazaddaruvala 2y ago

> CRDT literally means Conflict-free Replicated Data Type. Git could be "conflict-free" with a simple `rand(ours, theirs)`. It would be useless, but technically "conflict-free". Is the addition or removal of that rand function really, pragmatically the difference in the answer to "what is a CRDT?"

Groxx 2y ago
Adding extra rules on top of git to try to turn it into a CRDT doesn't make git one, even if you succeed (and rand would not succeed). You can do that with a pencil and paper, but that doesn't make paper a CRDT.
jakelazaroff 2y ago
`rand` wouldn’t work because all peers must reach the same state without coordination.
kiitos 2y ago
This is definitely not true. Are you open to understanding why this isn't true? If so, I'm happy to help you come to the correct understanding; please ask whatever questions are necessary. Otherwise, then, well, okay!

LAC-Tech 2y ago

There are CDTS that have "multiple versions", which look an awful lot like conflicts to me, ie, the Multi-Value Register in this paper: https://inria.hal.science/inria-00555588/ https://inria.hal.science/inria-00555588/

kiitos 2y ago
Multi-value registers are CRDTs for sure. Conflict-free doesn't mean that values can't have concurrent histories (or, as you say, "multiple versions") -- it means that the merge operation always succeeds.
- LAC-Tech 2y ago
  What's the definition of a conflict, then? Equations welcome.
  - kiitos 2y ago
    Feel free to read up on CRDTs; I'm confident this will answer your question. The short answer is, roughly, that a conflict is a discrepancy in state which cannot be mechanically resolved.
    - LAC-Tech 2y ago
      I've read a few CRDT papers. Perhaps you could name a specific one.