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Improve resizing log message #1939

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4aa9d98
Improve resizing log message
georgwiese Oct 23, 2024
8c401b6
Improve message, undo change in test
georgwiese Oct 23, 2024
f7435d6
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georgwiese Oct 25, 2024
6123923
Improve error message
georgwiese Oct 25, 2024
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13 changes: 2 additions & 11 deletions executor/src/witgen/machines/block_machine.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ use super::{EvalResult, FixedData, MachineParts};
use crate::witgen::affine_expression::AlgebraicVariable;
use crate::witgen::block_processor::BlockProcessor;
use crate::witgen::data_structures::finalizable_data::FinalizableData;
use crate::witgen::machines::compute_size_and_log;
use crate::witgen::processor::{OuterQuery, Processor};
use crate::witgen::rows::{Row, RowIndex, RowPair};
use crate::witgen::sequence_iterator::{
Expand Down Expand Up @@ -310,17 +311,7 @@ impl<'a, T: FieldElement> Machine<'a, T> for BlockMachine<'a, T> {
This might violate some internal constraints."
);
}

let new_degree = self.data.len().next_power_of_two() as DegreeType;
let new_degree = self.degree_range.fit(new_degree);
log::info!(
"Resizing variable length machine '{}': {} -> {} (rounded up from {})",
self.name,
self.degree,
new_degree,
self.data.len()
);
self.degree = new_degree;
self.degree = compute_size_and_log(&self.name, self.data.len(), self.degree_range);

if matches!(self.connection_type, ConnectionType::Permutation) {
// We have to make sure that *all* selectors are 0 in the dummy block,
Expand Down
13 changes: 2 additions & 11 deletions executor/src/witgen/machines/double_sorted_witness_machine_16.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ use std::iter::once;
use itertools::Itertools;

use super::{Machine, MachineParts};
use crate::witgen::machines::compute_size_and_log;
use crate::witgen::rows::RowPair;
use crate::witgen::util::try_to_simple_poly;
use crate::witgen::{EvalError, EvalResult, FixedData, MutableState, QueryCallback};
Expand Down Expand Up @@ -297,17 +298,7 @@ impl<'a, T: FieldElement> Machine<'a, T> for DoubleSortedWitnesses16<'a, T> {
set_selector(None);
}

let current_size = addr.len();
let new_size = current_size.next_power_of_two() as DegreeType;
let new_size = self.degree_range.fit(new_size);
log::info!(
"Resizing variable length machine '{}': {} -> {} (rounded up from {})",
self.name,
self.degree,
new_size,
current_size
);
self.degree = new_size;
self.degree = compute_size_and_log(&self.name, addr.len(), self.degree_range);

while addr.len() < self.degree as usize {
addr.push(*addr.last().unwrap());
Expand Down
13 changes: 2 additions & 11 deletions executor/src/witgen/machines/double_sorted_witness_machine_32.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ use std::iter::once;
use itertools::Itertools;

use super::{Machine, MachineParts};
use crate::witgen::machines::compute_size_and_log;
use crate::witgen::rows::RowPair;
use crate::witgen::util::try_to_simple_poly;
use crate::witgen::{EvalError, EvalResult, FixedData, MutableState, QueryCallback};
Expand Down Expand Up @@ -266,17 +267,7 @@ impl<'a, T: FieldElement> Machine<'a, T> for DoubleSortedWitnesses32<'a, T> {
set_selector(None);
}

let current_size = addr.len();
let new_size = current_size.next_power_of_two() as DegreeType;
let new_size = self.degree_range.fit(new_size);
log::info!(
"Resizing variable length machine '{}': {} -> {} (rounded up from {})",
self.name,
self.degree,
new_size,
current_size
);
self.degree = new_size;
self.degree = compute_size_and_log(&self.name, addr.len(), self.degree_range);

while addr.len() < self.degree as usize {
addr.push(*addr.last().unwrap());
Expand Down
25 changes: 25 additions & 0 deletions executor/src/witgen/machines/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ use powdr_ast::analyzed;
use powdr_ast::analyzed::DegreeRange;
use powdr_ast::analyzed::PolyID;

use powdr_number::DegreeType;
use powdr_number::FieldElement;

use crate::Identity;
Expand Down Expand Up @@ -214,3 +215,27 @@ impl<'a, T: FieldElement> MachineParts<'a, T> {
self.fixed_data.column_name(poly_id)
}
}

/// The minimum size for which a warning is logged if the used rows are less than half of the size.
/// This number coincides with 2**powdr_linker::MIN_DEGREE_LOG.
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It doesn't because there is no static_assert.

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Is it important that it does?

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It is not really important. If the total number of rows, the overhead of proving them becomes negligible and the log would just be noise. Arguably 32 is a already very small.
If this number was below 2**powdr_linker::MIN_DEGREE_LOG, we'd get the log message often, that's why I chose it to be equal.

Yesterday, we also discussed with Thibaut and Leo that we want to remove MIN_DEGREE_LOG and let the user always be explicit about the min degree. Then, this comment goes away.

/// It's probably not worth introducing a dependency to the linker just for this constant.
const MIN_REPORTING_SIZE: DegreeType = 32;

pub fn compute_size_and_log(name: &str, used_rows: usize, degree_range: DegreeRange) -> DegreeType {
let size = used_rows.next_power_of_two() as DegreeType;
let size = degree_range.fit(size);
let fraction_used = used_rows as f64 / size as f64;

if size > MIN_REPORTING_SIZE && fraction_used < 0.5 {
// In a machine configured to use VADCOP, we would expect the next power of two to be used.
let percentage = fraction_used * 100.0;
log::info!(
"Only {used_rows} of {size} rows ({percentage:.2}%) are used in machine '{name}', which is configured to support sizes in the range {degree_range}. \
If the min_degree of this machine was lower, we could size it down such that the fraction of used rows is at least 50%. \
If the backend supports it, consider lowering the min_degree.",
);
} else {
log::debug!("{used_rows} of {size} rows are used in machine '{name}'.");
}
size
}
16 changes: 6 additions & 10 deletions executor/src/witgen/vm_processor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ use std::cmp::max;
use std::time::Instant;

use crate::witgen::identity_processor::{self};
use crate::witgen::machines::compute_size_and_log;
use crate::witgen::IncompleteCause;
use crate::Identity;

Expand Down Expand Up @@ -180,17 +181,12 @@ impl<'a, 'b, 'c, T: FieldElement, Q: QueryCallback<T>> VmProcessor<'a, 'b, 'c, T
"Found loop with period {p} starting at row {row_index}"
);

let new_degree = self.processor.len().next_power_of_two() as DegreeType;
let new_degree = self.degree_range.fit(new_degree);
log::info!(
"Resizing variable length machine '{}': {} -> {} (rounded up from {})",
self.machine_name,
self.degree,
new_degree,
self.processor.len()
self.degree = compute_size_and_log(
&self.machine_name,
self.processor.len(),
self.degree_range,
);
self.degree = new_degree;
self.processor.set_size(new_degree);
self.processor.set_size(self.degree);
}
}
if let Some(period) = looping_period {
Expand Down