EIP 100: specify only the chosen version

This commit is contained in:
cdetrio 2017-08-15 15:36:53 -04:00
parent e136656cca
commit 04886529d4
1 changed files with 5 additions and 12 deletions

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@ -20,22 +20,15 @@ child_diff = int(max(parent.difficulty + (parent.difficulty // BLOCK_DIFF_FACTOR
If `block.number >= METROPOLIS_FORK_BLKNUM`, we change the first line to the following:
``` python
adj_factor = max(1 + len(parent.uncles) - ((timestamp - parent.timestamp) // 9), -99)
```
### Specification (1b)
``` python
adj_factor = max((2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9), -99)
```
### Rationale
This new formula ensures that the difficulty adjustment algorithm targets a constant average rate of blocks produced including uncles, and so ensures a highly predictable issuance rate that cannot be manipulated upward by manipulating the uncle rate. The formula can be fairly easily seen to be (to within a tolerance of ~3/4194304) mathematically equivalent to assuming that a block with `k` uncles is equivalent to a sequence of `k+1` blocks that all appear with the exact same timestamp, and this is likely the simplest possible way to accomplish the desired effect.
This new formula ensures that the difficulty adjustment algorithm targets a constant average rate of blocks produced including uncles, and so ensures a highly predictable issuance rate that cannot be manipulated upward by manipulating the uncle rate. A formula that accounts for the exact number of included uncles:
``` python
adj_factor = max(1 + len(parent.uncles) - ((timestamp - parent.timestamp) // 9), -99)
```
can be fairly easily seen to be (to within a tolerance of ~3/4194304) mathematically equivalent to assuming that a block with `k` uncles is equivalent to a sequence of `k+1` blocks that all appear with the exact same timestamp, and this is likely the simplest possible way to accomplish the desired effect. But since the exact formula depends on the full block and not just the header, we are instead using an approximate formula that accomplishes almost the same effect but has the benefit that it depends only on the block header (as you can check the uncle hash against the blank hash).
Changing the denominator from 10 to 9 ensures that the block time remains roughly the same (in fact, it should decrease by ~3% given the current uncle rate of 7%).
(1b) accomplishes almost the same effect but has the benefit that it depends only on the block header (as you can check the uncle hash against the blank hash) and not the entire block.
### Update 2017.06.29
Version (1b) was chosen.