Documentation
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Overview ¶
Package rangecheck implements range checking gadget
This package chooses the most optimal path for performing range checks:
- if the backend supports native range checking and the frontend exports the variables in the proprietary format by implementing frontend.Rangechecker, then use it directly;
- if the backend supports creating a commitment of variables by implementing frontend.Committer, then we use the log-derivative variant [Haböck22] of the product argument as in [BCG+18].
- lacking these, we perform binary decomposition of variable into bits.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func DecomposeHint ¶
DecomposeHint is a hint used for range checking with commitment. It decomposes large variables into chunks which can be individually range-check in the native range.
Types ¶
type Option ¶ added in v0.15.0
type Option func(*config) error
Option is a rangecheck option which allows to customize the rangecheck behavior.
func WithBaseLength ¶ added in v0.15.0
WithBaseLength sets the base length to use in the decomposition.
Normally, the committer-based rangechecker finds an optimal table size to minimize the number of constraints used for constructing the lookup table and performing the range checks. When the table size is smaller than the variable size, the variable is decomposed into chunks of size baseLength. We then perform range checks on each chunk and show that the initial variable is reconstructed from these chunks.
However, when the input variable does not fit exactly into chunks of size baseLength, the last chunk will be smaller. The range check on this last chunk is performed twice for the chunk and 2^(baselength-lastChunkSize) lastChunk. This means that for the last chunk we add two range checks instead of one, which can be suboptimal.
By setting the baseLength manually, the user can control the chunk size and avoid this double range check on the last chunk. For example, if the input variable is 10 bits long, setting baseLength to 5 will result in two chunks of size 5 bits each, and only one range check per chunk.
Note that this option only has an effect when using the committer-based rangechecker (i.e., when the backend implements frontend.Committer).
As the range checker is cached in the compiler context and we don't have a global initializer, then setting this option will override any previous setting for the range checker in the same context. Having conflicting options called in different parts of the code does not produce an error, but the last option called will take precedence. We will log a warning when this happens.
Source Files