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Fix rounding in demand placement #65

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Merged
networmix merged 1 commit into from
May 18, 2025
Merged

Fix rounding in demand placement #65

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17 changes: 16 additions & 1 deletion ngraph/lib/demand.py
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Original file line number Diff line number Diff line change
@@ -1,8 +1,10 @@
from __future__ import annotations

import math
from dataclasses import dataclass, field
from typing import Optional, Tuple

from ngraph.lib.algorithms.base import MIN_FLOW
from ngraph.lib.flow_policy import FlowPolicy
from ngraph.lib.graph import NodeID, StrictMultiDiGraph

Expand All @@ -21,6 +23,16 @@ class Demand:
flow_policy: Optional[FlowPolicy] = None
placed_demand: float = field(default=0.0, init=False)

@staticmethod
def _round_float(value: float) -> float:
"""Round ``value`` to avoid tiny floating point drift."""
if math.isfinite(value):
rounded = round(value, 12)
Comment on lines +26 to +30
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Copilot AI May 18, 2025

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[nitpick] The precision value 12 is a magic number. Extract this into a named constant (e.g., ROUND_PRECISION) or make it configurable to improve clarity and maintainability.

Suggested change
@staticmethod
def _round_float(value: float) -> float:
"""Round ``value`` to avoid tiny floating point drift."""
if math.isfinite(value):
rounded = round(value, 12)
# Precision for rounding floating-point values
ROUND_PRECISION: int = 12
@staticmethod
def _round_float(value: float) -> float:
"""Round ``value`` to avoid tiny floating point drift."""
if math.isfinite(value):
rounded = round(value, Demand.ROUND_PRECISION)

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if abs(rounded) < MIN_FLOW:
return 0.0
return rounded
return value

def __lt__(self, other: Demand) -> bool:
"""
Compare Demands by their demand_class (priority). A lower demand_class
Expand Down Expand Up @@ -94,7 +106,10 @@ def place(

# placed_now is the difference from the old placed_demand
placed_now = self.flow_policy.placed_demand - self.placed_demand
self.placed_demand = self.flow_policy.placed_demand
self.placed_demand = self._round_float(self.flow_policy.placed_demand)
remaining = to_place - placed_now

placed_now = self._round_float(placed_now)
remaining = self._round_float(remaining)

return placed_now, remaining