src/design.py

"""Experimental design of the dataset.

Every episode belongs to one *cell* of a full factorial design over five factors:

    topology family × nominal size × traffic profile × load level × dynamics level

Episode ``e`` maps deterministically to cell ``e mod n_cells`` and replicate ``e div n_cells``, so any
prefix of the episode range — and therefore any partially generated or resumed dataset — covers
all cells evenly. Replicates are assigned to train / validation / test splits (60 / 20 / 20).
The level definitions below are the design; ``SimConfig`` selects which levels to generate.
"""
from __future__ import annotations

from dataclasses import dataclass
from itertools import product
from typing import Dict, List, Tuple

TOPOLOGIES = ("barabasi_albert", "watts_strogatz", "erdos_renyi", "waxman", "fat_tree")
SIZES = (32, 64, 128, 256)          # nominal node count (fat-tree: k = 4, 6, 8, 10 → 36, 99, 208, 375 nodes)
SPLITS = ("train", "train", "train", "validation", "test")   # by replicate mod 5


@dataclass(frozen=True)
class TrafficProfile:
    """Two-state Markov-modulated Poisson process, parameterised by its mean rate m.

    With burst duty cycle d = mean_burst_steps / (mean_idle_steps + mean_burst_steps):
    idle_rate = m / ((1 − d) + d · peak_ratio),  burst_rate = peak_ratio · idle_rate,
    so the long-run mean rate equals m for every profile.
    """
    peak_ratio: float          # burst_rate / idle_rate (1 = stationary Poisson)
    mean_idle_steps: float
    mean_burst_steps: float

    @property
    def duty(self) -> float:
        return self.mean_burst_steps / (self.mean_idle_steps + self.mean_burst_steps)

    def rates(self, mean_rate: float) -> Tuple[float, float]:
        idle = mean_rate / ((1.0 - self.duty) + self.duty * self.peak_ratio)
        return idle, self.peak_ratio * idle


TRAFFIC_PROFILES: Dict[str, TrafficProfile] = {
    "poisson": TrafficProfile(peak_ratio=1.0, mean_idle_steps=100.0, mean_burst_steps=100.0),
    "microburst": TrafficProfile(peak_ratio=16.0, mean_idle_steps=100.0, mean_burst_steps=15.0),
    "sustained": TrafficProfile(peak_ratio=4.0, mean_idle_steps=100.0, mean_burst_steps=100.0),
}

# Offered load ρ = Σ_f m_f · hops_f / Σ_links capacity: the fraction of the network's directed link
# capacity that the flows would occupy on their shortest paths. Per-flow mean rates m_f are log-normal
# (σ = 0.75, "elephants and mice") and rescaled so that every episode meets its level exactly.
LOAD_LEVELS: Dict[str, float] = {
    "light": 0.01,
    "moderate": 0.03,
    "heavy": 0.10,
}
RATE_SIGMA = 0.75


@dataclass(frozen=True)
class Dynamics:
    link_failure_rate: float         # per-step probability that a non-bridge link fails
    node_degradation_rate: float     # per-step probability that a node degrades
    duration_range: Tuple[int, int]  # event duration, steps
    factor_range: Tuple[float, float]  # capacity multiplier of a degraded node's links


DYNAMICS_LEVELS: Dict[str, Dynamics] = {
    "static": Dynamics(0.0, 0.0, (0, 0), (1.0, 1.0)),
    "moderate": Dynamics(0.002, 0.002, (50, 200), (0.1, 0.5)),
    "severe": Dynamics(0.01, 0.01, (100, 400), (0.1, 0.5)),
}


@dataclass(frozen=True)
class Cell:
    topology: str
    size: int
    traffic_profile: str
    load_level: str
    dynamics_level: str

    @property
    def profile(self) -> TrafficProfile:
        return TRAFFIC_PROFILES[self.traffic_profile]

    @property
    def load(self) -> float:
        return LOAD_LEVELS[self.load_level]

    @property
    def dynamics(self) -> Dynamics:
        return DYNAMICS_LEVELS[self.dynamics_level]


def cells(topologies, sizes, traffic_profiles, load_levels, dynamics_levels) -> List[Cell]:
    return [Cell(*levels) for levels in product(topologies, sizes, traffic_profiles, load_levels, dynamics_levels)]


def locate(episode_id: int, n_cells: int) -> Tuple[int, int, str]:
    """(cell index, replicate, split) of an episode."""
    replicate = episode_id // n_cells
    return episode_id % n_cells, replicate, SPLITS[replicate % len(SPLITS)]