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chronon::TickSimulationConfig

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#include <TickSimulationConfig.hpp>

Public Types​

Name
enum classPartitionSolverType { Weighted, SA}

Public Attributes​

Name
booltrace_execution
SchedulerTimelineTraceConfigtimeline_trace
uint64_ttick_frequency_hz
1 GHz default.
doublesa_critical_path_weight
doublerebalance_min_gain
Skip rebalance if predicted gain below this fraction.
doublerebalance_imbalance_threshold
uint64_trebalance_cooldown_cycles
Minimum cycles between rebalances (0 disables cooldown).
uint64_trebalance_check_interval_cycles
PartitionSolverTypepartition_solver
size_tnum_threads
uint32_tmax_lookahead_cycles
doubleinitial_partition_sync_cost_ns
uint64_tepoch_size
boolenable_weighted_partitioning
boolenable_parallel
boolenable_lookahead
boolenable_epoch_free_lookahead
boolenable_dynamic_rebalance

Detailed Description​

struct chronon::TickSimulationConfig;

Configuration for tick-based simulation.

Placement (initialization-time) vs. scheduling (runtime) are orthogonal. Placement groups units into clusters; scheduling decides how those clusters advance in time. cluster.size() == 1 is the fallback for un-clustered topologies — the scheduler treats the two uniformly.

Public Types Documentation​

enum PartitionSolverType​

EnumeratorValueDescription
Weighted
SA

Initial partition solver used by the cluster-aware path. SA is the default; Weighted keeps the deterministic four-phase solver available.

Public Attributes Documentation​

variable trace_execution​

bool trace_execution = false;

variable timeline_trace​

SchedulerTimelineTraceConfig timeline_trace;

variable tick_frequency_hz​

uint64_t tick_frequency_hz = 1'000'000'000;

1 GHz default.

variable sa_critical_path_weight​

double sa_critical_path_weight = 0.0;

SA objective critical-path term weight applied to max per-thread chain cost (ns). 0 disables the term (default).

variable rebalance_min_gain​

double rebalance_min_gain = 0.01;

Skip rebalance if predicted gain below this fraction.

variable rebalance_imbalance_threshold​

double rebalance_imbalance_threshold = 1.03;

variable rebalance_cooldown_cycles​

uint64_t rebalance_cooldown_cycles =
        0;

Minimum cycles between rebalances (0 disables cooldown).

variable rebalance_check_interval_cycles​

uint64_t rebalance_check_interval_cycles = 2048;

variable partition_solver​

PartitionSolverType partition_solver = PartitionSolverType::SA;

variable num_threads​

size_t num_threads = std::thread::hardware_concurrency();

variable max_lookahead_cycles​

uint32_t max_lookahead_cycles = 100;

variable initial_partition_sync_cost_ns​

double initial_partition_sync_cost_ns = 8.0;

Fixed, wall-clock-free sync cost (ns) fed ONLY to the initial deterministic partition so the solver minimizes cross-thread edge cut, co-locating topologically-connected units (e.g. a CPU core's pipeline) on one thread. Scaled to dominate the uniform unit cost (1.0) — empirically ~8x is the sweet spot: large enough to pull connected components together, small enough that the compute-balance signal still steers the SA solver (much higher swamps it and convergence degrades). 0 restores the old pure-load-balance behavior.

This knob is scoped to the initial partition: it is not written into platform_metrics_, so dynamic rebalance decides migrations on its own inputs (measured unit costs + platform_metrics_) and is unaffected by it.

variable epoch_size​

uint64_t epoch_size = 64;

Deprecated compatibility knob for the per-epoch lookahead fallback. Epoch-free lookahead ignores this value; it will be removed or ignored once the fallback scheduler is removed.

variable enable_weighted_partitioning​

bool enable_weighted_partitioning = true;

Enables the cluster-aware partitioning path. When false, Chronon falls back to the legacy topology-only thread assignment.

variable enable_parallel​

bool enable_parallel = true;

Scheduler selection:

  • !enable_parallel → Sequential (single-thread)
  • enable_parallel && !enable_lookahead → Barrier (per-cycle sync)
  • enable_parallel && enable_lookahead → Lookahead (per-cluster atomics)

variable enable_lookahead​

bool enable_lookahead = true;

variable enable_epoch_free_lookahead​

bool enable_epoch_free_lookahead = true;

Epoch-free lookahead: in the persistent-worker lookahead path, collapse the per-epoch std::barrier into a single run-spanning window. Run-ahead is then bounded by lookahead_floor_ + max_lookahead_cycles plus per-edge queue-headroom dependencies, with per-connection MPSC arbitration and a single MPSC flush at run end. Engaged by runParallel() only when the persistent path is eligible, max_lookahead_cycles is positive, and every MPSC port has fully resolved per-connection progress; otherwise it falls back to the barrier path. Results are identical to the barrier path — it trades per-epoch straggler idle for lookahead-window slack.

Setting this to false selects the deprecated per-epoch lookahead fallback. That fallback is retained for compatibility and will be removed in a future release.

variable enable_dynamic_rebalance​

bool enable_dynamic_rebalance = true;

Updated on 2026-07-06 at 09:03:34 +0000