This currently matches the first region on the row that matches any
input column, which will result in some mismatches. To fix this, we will
need to track the columns of complex selectors.
Due to this error being detected and returned early, in practice
`minimum_k` would always be `current_k + 1`, and the error would be
returned repeatedly (as more of the circuit could be processed) until
`k` was set large enough. We now simply suggest that the user try a
larger value of `k`.
During circuit configuration, fixed columns can be marked as suitable
for containing arbitrary constant values (i.e. the columns aren't
encumbered by constraints that preclude arbitrary values).
During synthesis, circuits can now request that the layouter assign
an advice cell within a region, to some specified constant value. It
is the layouter's responsibility to find space within the previously
marked fixed columns, in which to assign the constant.
This commit intentionally does not compile.
Circuit developers need to use selectors (or equivalent) to prevent their
custom gates from being active on unusable rows. By marking the advice
cells in these rows as "poisoned" and tracking this through expressions,
we can provide a better error message to developers that indicates the
missing selector issue.
Closeszcash/halo2#329.
This is the beginning of the process to enable full floor planning
capabilities in `halo2`. For now, all that a floor planner can do is
synthesize a circuit, which makes it no more powerful than a layouter,
but easier to use (as moving to a multi-pass layouter no longer requires
changes to `Circuit::synthesize`).
This is more useful for developers, as the absolute cell row may be
obfuscated by the layouter, whereas the offset within a row is controlled
by the developer.
Current layouters measure the shape of regions by looking at the cells
they assign. If a chip developer forgets to assign a cell in a region,
it is possible for active gates to "stick out" past the edge of a
measured region shape.
`MockProver` checks that all active gates have their cells assigned,
but this was previously checked globally. If a layouter happened to
position the buggy region such that the dangling gate overlapped an
assigned cell in in adjacent region, this check would pass.
In this commit, we extend the check to be per-region. We map enabled
selectors and assigned cells to a specific region, and then if a gate
is active within a region, we require that its cells be assigned within
that same region.
Closeszcash/halo2#297.
therealyingtong
Jack Grigg
Daira Hopwood
Sean Bowe