Class TLcdNumericGraphEncoder
 All Implemented Interfaces:
ILcdOutputStreamFactoryCapable
Exporting graphs
Multileveled partitioned graphs can be converted into numerical graphs via this encoder. During the export phase, each partition, node and edge is mapped onto a numerical counterpart, computed by the encoder (see the documentation ofTLcdNumericGraph
for a description of
how these numerical identifiers are computed).
The result will be written to disk incrementally, to allow processing of very large graphs which do not fit completely in memory.
All mappings are reported to the user via a ILcdNumericGraphMappingHandler
callback.
If the graph is exported with an edge value function, the encoder will automatically encode the edge values and compute and encode the distance tables as well.
Saving graphs
The encoder allows saving numerical graphs to the location they were decoded from. Only the files that have changed (due to changes in the graph) will be saved. For optimal performance, it is important to split up very large graphs in multiple files.File format
The following files are written to disk:
 *.ng: topology files, describing the topological structure of the graph  the partitions, nodes, edges and their connectivity.
 *.ngv: edge value files, containing the edge values for all edges in the topology files.
 *.ngd: distance table files, containing the distance tables for the topology+edge value files.
Splitting files
The encoder allows splitting up the graph's data in multiple files. Splitting is done at partition level. Two mechanisms are provided to control the splitting process: Node split threshold: a partition is only saved in a separate file if it contains at least as many nodes as the node split threshold.
 Split levels: a partition is only saved in a separate file if its hierarchical level within the graph structure is one of the specified split levels.
Value Encoding format
Edge value encoding takes up a considerable part of the graph's size on disk. The edge value encoding can therefore be configured to obtain smaller files. See theTLcdNumericGraphEncoder.EdgeValueEncoding
documentation
for more information on the available encodings. Since:
 9.1

Nested Class Summary
Modifier and TypeClassDescriptionstatic enum
Enumeration describing the encoding of edge values. 
Constructor Summary

Method Summary
Modifier and TypeMethodDescription<N,
E> void exportEdgeValueFunction
(ILcdGraph<N, E> aGraph, ILcdEdgeValueFunction<N, E> aEdgeValueFunction, String aTopologySourceName, String aEdgeValuesDestinationName) Exports the specified edge value function for the specified graph.<N,
E> void exportGraph
(ILcdGraph<N, E> aGraph, ILcdEdgeValueFunction<N, E> aEdgeValueFunction, ILcdNumericGraphMappingHandler<N, E> aMappingHandler, String aTopologyDestinationName, String aEdgeValuesDestinationName) Export the specified graph and edge value function to a numeric graph.Returns the encoding mode for encoding edge values.int
Returns the number of extra slots that is reserved in each partition for adding extra edges after the graph has been converted to a numeric graph.int[]
Return for each level in the graph hierarchy the minimum number of nodes a partition should have before being encoded to a separate file.Returns thecom.luciad.io.ILcdOutputStreamFactory
which is used for creating output streams.void
saveGraph
(TLcdNumericGraph aGraph) Saves a numeric graph to the location it was decoded from.void
setEdgeValueEncoding
(TLcdNumericGraphEncoder.EdgeValueEncoding aValueEncoding) Sets the encoding mode for encoding edge values.void
setExpansionSize
(int aExpansionSize) Sets the number of extra slots to be reserved in each partition for adding extra edges after the graph has been converted to a numeric graph.void
setNodeSplitThresholds
(int[] aNodeSplitThresholds) Sets for each level in the graph hierarchy the minimum number of nodes a partition should have before being encoded to a separate file.void
setOutputStreamFactory
(ILcdOutputStreamFactory aOutputStreamFactory) Sets thecom.luciad.io.ILcdOutputStreamFactory
to be used for creating output streams.

Constructor Details

TLcdNumericGraphEncoder
public TLcdNumericGraphEncoder()


Method Details

setExpansionSize
public void setExpansionSize(int aExpansionSize) Sets the number of extra slots to be reserved in each partition for adding extra edges after the graph has been converted to a numeric graph. The default value is 100. The higher this number, the more bits in the numerical id's will be reserved for future use by extra edges. If this number is set too high, the encoder might not be able to generate enough id's for all edges and nodes. Parameters:
aExpansionSize
 the number of extra slots to be reserved in each partition for adding extra edges after the graph has been converted to a numeric graph. See Also:

getExpansionSize
public int getExpansionSize()Returns the number of extra slots that is reserved in each partition for adding extra edges after the graph has been converted to a numeric graph. The default value is 100. Returns:
 the number of extra slots to be reserved in each partition for adding extra edges after the graph has been converted to a numeric graph.
 See Also:

getEdgeValueEncoding
Returns the encoding mode for encoding edge values. Returns:
 the encoding mode for encoding edge values.
 See Also:

setEdgeValueEncoding
Sets the encoding mode for encoding edge values. The default isTLcdNumericGraphEncoder.EdgeValueEncoding.STANDARD
. Parameters:
aValueEncoding
 the encoding mode for encoding edge values. See Also:

setNodeSplitThresholds
public void setNodeSplitThresholds(int[] aNodeSplitThresholds) Sets for each level in the graph hierarchy the minimum number of nodes a partition should have before being encoded to a separate file. If a partition has a number of nodes larger than the specified threshold, the partition's data will be encoded to separate files. Hierarchical levels with value1
or beyond the size of the specified array will never be split.The default split configuration is {1,1000} (partitions on the highest level will never be split, partitions on the second level will be split if the number of nodes is larger than 1000, lower level partitions will never be split).
 Parameters:
aNodeSplitThresholds
 the array with node split thresholds for which a file split should be considered. See Also:

getNodeSplitThresholds
public int[] getNodeSplitThresholds()Return for each level in the graph hierarchy the minimum number of nodes a partition should have before being encoded to a separate file. Returns:
 the array with node split thresholds for which a file split should be considered.
 See Also:

getOutputStreamFactory
Returns thecom.luciad.io.ILcdOutputStreamFactory
which is used for creating output streams. Specified by:
getOutputStreamFactory
in interfaceILcdOutputStreamFactoryCapable
 Returns:
 the output stream factory which is used for creating output streams.
 See Also:

setOutputStreamFactory
Sets thecom.luciad.io.ILcdOutputStreamFactory
to be used for creating output streams. By default, acom.luciad.io.TLcdFileOutputStreamFactory
is used. Specified by:
setOutputStreamFactory
in interfaceILcdOutputStreamFactoryCapable
 Parameters:
aOutputStreamFactory
 the factory to be used for creating output streams. See Also:

exportGraph
public <N,E> void exportGraph(ILcdGraph<N, E> aGraph, ILcdEdgeValueFunction<N, throws IOExceptionE> aEdgeValueFunction, ILcdNumericGraphMappingHandler<N, E> aMappingHandler, String aTopologyDestinationName, String aEdgeValuesDestinationName) Export the specified graph and edge value function to a numeric graph.This method performs the following actions:
 It converts the specified graph to a numeric graph.
 It computes for each edge in the graph its forward and backward edge value using the specified edge value function.
 The topology (partitions, nodes, connecting edges) of the numeric graph, together with the edge values, are stored in one or more output streams.
 For each partition in the graph, the distance table is computed. If the graph is multileveled, the distance tables will be computed recursively for all levels.
 The distance tables are all stored using output streams.
Every mapping from a node or edge to a corresponding numeric identifier in the destination numeric graph is reported to the
com.luciad.network.graph.numeric.ILcdNumericGraphMappingHandler
that is specified. Parameters:
aGraph
 the graph to be converted to a numeric graph.aEdgeValueFunction
 the edge value function describing the weights of the edges in the graph.aMappingHandler
 the mapping handler to which all node and edge mappings should be reported.aTopologyDestinationName
 the destination name for the main graph file.aEdgeValuesDestinationName
 the destination name for the main graph values file. Throws:
IOException
 if an I/O exception occurs while exporting.

saveGraph
Saves a numeric graph to the location it was decoded from. Only the files that have been changed will be overwritten. Parameters:
aGraph
 the graph to be saved. Throws:
IOException
 if an I/O exception occurs while saving.

exportEdgeValueFunction
public <N,E> void exportEdgeValueFunction(ILcdGraph<N, E> aGraph, ILcdEdgeValueFunction<N, throws IOExceptionE> aEdgeValueFunction, String aTopologySourceName, String aEdgeValuesDestinationName) Exports the specified edge value function for the specified graph. This can only be done if the graph has already been exported to a numeric graph in a previous step. The graph topology files will remain untouched.Note that the specified graph should be the original graph, not the numeric graph resulting from a previous export! It is important that the
getNodes()
,getEdges()
andgetPartitions()
methods return the same sequence (same order) of nodes/edges/partitions, as during the original encoding. Also, the encoding parameters (node split threshold, split levels and expansion size) should be identical to the ones used during the original encoding. Parameters:
aGraph
 the graph for which to export an edge value function.aEdgeValueFunction
 the edge value function to export.aTopologySourceName
 the location of the main graph topology file.aEdgeValuesDestinationName
 the location of the main edge value file where the values should be stored. Throws:
IOException
 if an I/O exception occurs while exporting.
