[#cluster_linearize-SFLDefaultCostModel]
= xref:cluster_linearize.adoc[cluster_linearize]::SFLDefaultCostModel
:relfileprefix: ../
:mrdocs:

A default cost model for SFL for SetType=BitSet<64>, based on benchmarks.

== Synopsis

Declared in `<cluster_linearize.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class SFLDefaultCostModel;
----

== Description

The numbers here were obtained in February 2026 by:

* For a variety of machines:
* Running a fixed collection of ~385000 clusters found through random generation and fuzzing, optimizing for difficulty of linearization.
* Linearize each ~3000 times, with different random seeds. Sometimes without input linearization, sometimes with a bad one.
* Gather cycle counts for each of the operations included in this cost model, broken down by their parameters.
* Correct the data by subtracting the runtime of obtaining the cycle count.
* Drop the 5% top and bottom samples from each cycle count dataset, and compute the average of the remaining samples.
* For each operation, fit a least‐squares linear function approximation through the samples.
* Rescale all machine expressions to make their total time match, as we only care about relative cost of each operation.
* Take the per‐operation average of operation expressions across all machines, to construct expressions for an average machine.
* Approximate the result with integer coefficients. Each cost unit corresponds to somewhere between 0.5 ns and 2.5 ns, depending on the hardware.

== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:cluster_linearize/SFLDefaultCostModel/ActivateBegin.adoc[`ActivateBegin`] 
| Marks the start of activating a dependency.
| xref:cluster_linearize/SFLDefaultCostModel/ActivateEnd.adoc[`ActivateEnd`] 
| Accounts for the cost of activating a dependency.
| xref:cluster_linearize/SFLDefaultCostModel/DeactivateBegin.adoc[`DeactivateBegin`] 
| Marks the start of deactivating a dependency.
| xref:cluster_linearize/SFLDefaultCostModel/DeactivateEnd.adoc[`DeactivateEnd`] 
| Accounts for the cost of deactivating a dependency.
| xref:cluster_linearize/SFLDefaultCostModel/GetCost.adoc[`GetCost`] 
| Returns the accumulated cost.
| xref:cluster_linearize/SFLDefaultCostModel/GetLinearizationBegin.adoc[`GetLinearizationBegin`] 
| Marks the start of extracting the linearization.
| xref:cluster_linearize/SFLDefaultCostModel/GetLinearizationEnd.adoc[`GetLinearizationEnd`] 
| Marks the end of extracting the linearization (cost already charged in InitializeEnd).
| xref:cluster_linearize/SFLDefaultCostModel/InitializeBegin.adoc[`InitializeBegin`] 
| Marks the start of the initialization phase.
| xref:cluster_linearize/SFLDefaultCostModel/InitializeEnd.adoc[`InitializeEnd`] 
| Accounts for the cost of initialization and of the final linearization.
| xref:cluster_linearize/SFLDefaultCostModel/MakeTopologicalBegin.adoc[`MakeTopologicalBegin`] 
| Marks the start of making the linearization topological.
| xref:cluster_linearize/SFLDefaultCostModel/MakeTopologicalEnd.adoc[`MakeTopologicalEnd`] 
| Accounts for the cost of making the linearization topological.
| xref:cluster_linearize/SFLDefaultCostModel/MergeChunksBegin.adoc[`MergeChunksBegin`] 
| Marks the start of merging chunks.
| xref:cluster_linearize/SFLDefaultCostModel/MergeChunksEnd.adoc[`MergeChunksEnd`] 
| Accounts for the per‐step cost of merging chunks.
| xref:cluster_linearize/SFLDefaultCostModel/MergeChunksMid.adoc[`MergeChunksMid`] 
| Accounts for the per‐transaction cost of merging chunks.
| xref:cluster_linearize/SFLDefaultCostModel/MinimizeStepBegin.adoc[`MinimizeStepBegin`] 
| Marks the start of a single minimization step.
| xref:cluster_linearize/SFLDefaultCostModel/MinimizeStepEnd.adoc[`MinimizeStepEnd`] 
| Accounts for the cost of finishing a minimization step.
| xref:cluster_linearize/SFLDefaultCostModel/MinimizeStepMid.adoc[`MinimizeStepMid`] 
| Accounts for the per‐transaction cost of a minimization step.
| xref:cluster_linearize/SFLDefaultCostModel/PickChunkToOptimizeBegin.adoc[`PickChunkToOptimizeBegin`] 
| Marks the start of picking a chunk to optimize.
| xref:cluster_linearize/SFLDefaultCostModel/PickChunkToOptimizeEnd.adoc[`PickChunkToOptimizeEnd`] 
| Accounts for the cost of picking a chunk to optimize.
| xref:cluster_linearize/SFLDefaultCostModel/PickDependencyToSplitBegin.adoc[`PickDependencyToSplitBegin`] 
| Marks the start of picking a dependency to split.
| xref:cluster_linearize/SFLDefaultCostModel/PickDependencyToSplitEnd.adoc[`PickDependencyToSplitEnd`] 
| Accounts for the cost of picking a dependency to split.
| xref:cluster_linearize/SFLDefaultCostModel/PickMergeCandidateBegin.adoc[`PickMergeCandidateBegin`] 
| Marks the start of picking a merge candidate.
| xref:cluster_linearize/SFLDefaultCostModel/PickMergeCandidateEnd.adoc[`PickMergeCandidateEnd`] 
| Accounts for the cost of picking a merge candidate.
| xref:cluster_linearize/SFLDefaultCostModel/StartMinimizingBegin.adoc[`StartMinimizingBegin`] 
| Marks the start of a minimization pass.
| xref:cluster_linearize/SFLDefaultCostModel/StartMinimizingEnd.adoc[`StartMinimizingEnd`] 
| Accounts for the cost of starting a minimization pass.
| xref:cluster_linearize/SFLDefaultCostModel/StartOptimizingBegin.adoc[`StartOptimizingBegin`] 
| Marks the start of setting up an optimization round.
| xref:cluster_linearize/SFLDefaultCostModel/StartOptimizingEnd.adoc[`StartOptimizingEnd`] 
| Accounts for the cost of setting up an optimization round.
|===



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