Merger Tree Build Controllers

Class providing merger tree build controllers—logic objects that govern when and how the tree builder places new nodes during tree construction. A controller decides whether a given node should be continued (branched further), constrains the range of allowed “times” (\(w(t) = \delta_\mathrm{c}(t)/D(t)\)) at each node, forces node insertion at specified times, and supplies the branching probability object to use. Controllers enable constrained trees, main-branch-only trees, and other specialized constructions.

Default implementation: mergerTreeBuildControllerUncontrolled

Methods

control → logical

Control the behavior of a tree build.

  • type (treeNode ), intent(inout), pointer :: node

  • class(mergerTreeWalkerClass), intent(inout), optional :: treeWalker_

timeMinimum → double precision

Return the minimum “time” (using the usual \(w\) variable for merger tree building) allowed for this node.

  • type (treeNode), intent(inout) :: node

  • double precision , intent(in ) :: massBranch, criticalOverdensityBranch

timeMaximum → double precision

Return the maximum “time” (using the usual \(w\) variable for merger tree building) allowed for this node.

  • type (treeNode), intent(inout) :: node

  • double precision , intent(in ) :: massBranch, criticalOverdensityBranch, timeReference

  • logical , intent( out) :: insertNode

controlTimeMaximum → logical

Control the behavior of a tree build when the maximum time for a node is reached.

  • type (treeNode ), intent(inout), target :: node

  • double precision , intent(in ) :: massBranch, criticalOverdensityBranch

  • integer (kind_int8), intent(inout) :: nodeIndex

branchingProbabilityObject → class(mergerTreeBranchingProbabilityClass)

Return a branching probability object to use in tree building.

  • type(treeNode), intent(inout) :: node

nodesInserted → void

Alert the controller when new nodes are inserted into the tree.

  • type (treeNode), intent(inout) :: nodeCurrent , nodeProgenitor1

  • type (treeNode), intent(inout), optional :: nodeProgenitor2

  • logical , intent(in ), optional :: didBranch

mergerTreeBuildControllerBranchless

A merger tree build controller class which builds branchless trees.

mergerTreeBuildControllerConstrained

A merger tree build controller class which builds constrained merger trees using a Brownian bridge approach, enforcing specified overdensity and mass constraints at a target redshift. Controls which branches are built via the [constructionOption] parameter, with Brownian bridge endpoints set by [criticalOverdensity], [variance], [redshift], and [haloMass].

Parameters

  • [trialCountMaximum] (default huge(1_c_size_t)) — The maximum number of trials to attempt before failing.

  • [label] (default var_str(' ')) — A label to apply to the constrained node.

  • [labelDescription] — A human-readable description of the label applied to constrained nodes in the merger tree, used to document what physical property or criterion the label represents.

  • [constructionOption] — Controls which branches of the tree to build.

  • [criticalOverdensityConstrained] — The critical overdensity at the end of the Brownian bridge.

  • [varianceConstrained] — The variance at the end of the Brownian bridge.

  • [redshiftConstrained] — The redshift at the end of the Brownian bridge.

  • [massConstrained] — The halo mass at the end of the Brownian bridge.

mergerTreeBuildControllerFiltered

A merger tree build controller class which builds filtered trees.

mergerTreeBuildControllerMainBranch

A merger tree build controller class which builds trees containing only the main branch and progenitors of the node on the main branch above a certain mass fraction. Specifically, if a progenitor node of the node on the main branch has a mass below a certain mass fraction relative to the main branch node, the branch will not grow any further.

Parameters

  • [massFraction] (default 0.0d0) — Mass fraction relative to the descendant node on the main branch below which the progenitor branch does not grow any further.

  • [invertFilter] (default .false.) — If true, the filter is inverted to pass only nodes not on the main branch.

  • [includeSubhalos] (default .false.) — If set to true then subhalos of the main branch halo are also assigned a value of 1 (with subhalos of non-main branch halos assigned a value of 0). Otherwise, all subhalos are assigned a value of 0.

mergerTreeBuildControllerMassTimeWindow

A merger tree build controller class which follows branches only if they lie within a window of time and mass.

Methods

  • passes — Returns true if the given node lies within the allowed window.

Parameters

  • [massMinimum] — The minimum mass to which branches should be followed.

  • [timeMinimum] — The minimum time to which branches should be followed.

  • [redshiftMaximum] — The maximum redshift to which branches should be followed.

mergerTreeBuildControllerMulti

A merger tree build controller class which applies multiple other controllers.

Methods

  • columnDescriptions — Return a description of the columns.

  • elementCount — Return the number of properties in the tuple.

  • extractDouble — Extract the double properties from the given node.

  • extractInteger — Extract the integer properties from the given node.

  • names — Return the names of the properties extracted.

  • descriptions — Return descriptions of the properties extracted.

  • unitsInSI — Return the units of the properties extracted in the SI system.

  • units — Return an object containing units metadata for the properties.

  • ranks — Return the ranks of the properties extracted.

  • metaData — Populate a hash with meta-data for the property.

mergerTreeBuildControllerOutputTimeSnap

A merger tree build controller class that forces tree time steps to exactly coincidence with output times.

mergerTreeBuildControllerSingleStep

A merger tree build controller class which limits the building of a merger tree to a single step, advancing to a specified target redshift set by [redshift]. After the step, tree building either halts or continues without further step limitations depending on the [haltAfterStep] parameter.

Parameters

  • [redshiftStep] — The redshift to which to take a single step.

  • [haltAfterStep] (default .true.) — If true, cease building the tree after the first step. Otherwise, continue to build with no further step limitations.

mergerTreeBuildControllerSubsample

A merger tree build controller class which performs probabilistic subsampling of branches during tree construction, retaining low-mass branches with a mass-dependent probability \(P(M) = P_0 (M/M_0)^\alpha\) for \(M < M_0\). The mass threshold \(M_0\), sampling rate \(P_0\), and exponent \(\alpha\) are set by [massThreshold], [subsamplingRateAtThreshold], and [exponent], with node weights adjusted to compensate.

Parameters

  • [massThreshold] — The mass threshold, \(M_0\), below which subsampling is applied.

  • [fractionMassThreshold] — The fractional (relative to the tree mass) mass threshold, \(f_0\), below which subsampling is applied.

  • [subsamplingRateAtThreshold] — The subsampling rate at the mass threshold, \(P_0\).

  • [exponent] — The exponent, \(\alpha\), of mass in the subsampling probability, i.e. \(P(M) = P_0 (M/M_0)^\alpha\) for \(M < M_0\).

  • [factorMassGrowthConsolidate] (default 0.0d0) — The maximum factor by which the mass is allowed to grow between child and parent when consolidating nodes. A non-positive value prevents consolidation.

  • [destroyStubs] (default var_str('always')) — Parameter controlling when to destroy stub branches. Options are always, never, and sideBranchesOnly.

  • [rate] — The probability (between 0 and 1) that each particle is retained; particles are drawn independently from a uniform distribution to achieve the target subsampling fraction.

mergerTreeBuildControllerUncontrolled

A merger tree build controller class which provides no control.

(Default implementation)