#!F-adobe-helvetica-medium-r-normal--18*
#!N
#!CNavyBlue #!N #!Rgns Growing and Shrinking Partitioned
Data #!N #!EC #!N #!N The routines listed at the end
of this section are necessary for processing Composite Fields. #!N #!N
Some modules (e.g., filters) require information from the neighborhood of each
point. Since partitioning divides data into spatially disjoint subsets for independent
processing, a neighborhood may be divided among different partitions: for example,
a filter kernel may overlap the boundary between two partitions. In
such cases, processing one partition requires information that resides in the
other. #!N #!N In order to facilitate such information sharing, Data
Explorer includes routines that support temporarily overlapping partitions. #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF
modifies its input Field and adds to each partition information from
the partition's neighbor(s). #!N #!N Because #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF modifies its
input, the calling routine must use #!F-adobe-times-bold-r-normal--18* DXCopy() #!EF to copy
the input structure if that structure is not to be modified.
After this boundary information has been accrued, the processing of the
partition may be handled independently since all information required to produce
correct results for the original partition is available in it. For
example, in the case of filtering, boundary information is added so
that wherever a filter kernel is placed in the original partition,
the kernel does not extend outside the grown partition, producing correct
results in the original partition. After processing the Field produced by
#!F-adobe-times-bold-r-normal--18* DXGrow() #!EF , #!F-adobe-times-bold-r-normal--18* DXShrink() #!EF must be called to
shrink any components that have not been shrunk by the caller,
and to remove extra references to the original components that were
put in the Field by #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF . #!N #!N
When #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF is called, the depth of an overlap
region is specified by specifying the number of #!F-adobe-times-medium-i-normal--18* rings #!EF
to be accrued. An element is said to be in the
#!F-adobe-times-medium-i-normal--18* k #!EF th ring if it has at least one
vertex in the #!F-adobe-times-medium-i-normal--18* k #!EF th ring. A vertex is
in the 0th ring if it exists both in the partition
and the neighbor, and is in the #!F-adobe-times-medium-i-normal--18* k #!EF th
ring if it is not in a lower ring and an
element in ring #!F-adobe-times-medium-i-normal--18* k-1 #!EF is incident upon it. Most
frequently, such modules produce results for each vertex on the basis
of the elements incident on that vertex; this is achieved by
requesting that #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF include 1 ring: those elements from
neighboring partitions that are incident on vertices that exist in both
partitions. #!N The treatment of the exterior boundary of regular grid
data is specified by a parameter to #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF .
You may specify that the Field not be expanded beyond its
boundary (i.e., that the exterior partitions not be expanded except on
the sides that border other partitions). Alternatively you may specify that
the Field be expanded beyond its original boundaries, with the new
data being filled in one of three ways: with a constant
value; with the replicated value from the nearest edge point in
the original Field; or with nothing, only reserving space for the
new data but leaving its contents undefined. #!N #!N While it
is necessary that the footprint of a filter kernel, placed anywhere
in the original partition, not extend past the grown partition boundary,
it is probably not necessary to apply the filter in the
boundary regions accrued from neighbors; these regions are properly handled during
the processing of the neighboring partition. Data Explorer also includes routines
that query the original number of positions and connections (in the
case of irregular grids) or the offset relative to the grown
partition and size of the original partition. #!N #!N Frequently, modules
do not require all components of a Field that are dependent
on the positions to be grown. To avoid accruing information that
will not be required during processing, #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF requires the
calling application to specify which components, in addition to positions and
connections, will be required. #!N #!N Modules using #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF
have the option of producing results corresponding to the positions of
the larger grown Field or, more efficiently, producing results corresponding only
to positions of the original smaller Field. Even though the former
method is less efficient, involving more data movement and perhaps more
calculation, it is sometimes more convenient. Therefore, the #!F-adobe-times-bold-r-normal--18* DXShrink() #!EF
function is provided to shrink all components that depend on or
reference positions or connections back to their original size. If the
user has already shrunk the positions, #!F-adobe-times-bold-r-normal--18* DXShrink() #!EF will leave
them unmodified. In any case, the #!F-adobe-times-bold-r-normal--18* DXShrink() #!EF function must
be called after operating on a grown Field in order to
remove references to the "original" components that were placed in the
Field by #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF for later use by #!F-adobe-times-bold-r-normal--18* DXShrink()
#!EF . #!N #!N For each component specified in the component
list passed to #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF , a component named "original
#!F-adobe-times-medium-i-normal--18* componentname #!EF " is created. #!F-adobe-times-bold-r-normal--18* DXShrink() #!EF will rename
each of these to its original name. Therefore, for components you
have modified (e.g., data), you should remove the corresponding original component
("original data" in this example) before calling #!F-adobe-times-bold-r-normal--18* DXShrink() #!EF .
#!N Both #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF and #!F-adobe-times-bold-r-normal--18* DXShrink() #!EF operate in
parallel on Composite Fields. For that reason, #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF must
be called prior to any subtasking invoked explicitly by the calling
application; #!F-adobe-times-bold-r-normal--18* DXShrink() #!EF must be called after any such subtasking
has been completed. #!CForestGreen #!N #!N #!F-adobe-courier-bold-r-normal--18* #!N #define GROW_NONE NULL
#!N #define GROW_REPLICATE ((Pointer)1) #!N #define GROW_NOFILL ((Pointer)2) #!EF #!N #!N
#!EC #!N #!I0 #!N #!N #!I0 #!N #!F-adobe-times-bold-r-normal--18* #!F-adobe-times-bold-r-normal--18* Object DXGrow()
#!EF #!N Object DXGrowV(); #!EF #!I50 #!N Add information from neighboring
partitions to a Composite Field. See #!Ldxgrov,dxall1273 h DXGrow, DXGrowV #!EL . #!N #!I0 #!N
#!F-adobe-times-bold-r-normal--18* #!F-adobe-times-bold-r-normal--18* Field DXQueryOriginalSizes() #!EF #!N Field DXQueryOriginalMeshExtents(); #!EF #!I50 #!N
Return information about the size of the original Field used as
the input to #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF . See #!Ldxqosm,dxall1346 h DXQueryOriginalSizes, DXQueryOriginalMeshExtents #!EL . #!N
#!I0 #!N #!F-adobe-times-bold-r-normal--18* #!F-adobe-times-bold-r-normal--18* Object DXShrink() #!EF #!EF #!I50 #!N Removes
information added to an Object by #!F-adobe-times-bold-r-normal--18* DXGrow() #!EF . See
#!Ldxsk,dxall1395 h DXShrink #!EL . #!I0 #!N #!N #!N #!N #!N #!F-adobe-times-medium-i-normal--18* Next Topic
#!EF #!N #!N #!Lhash,dxall1121 h Hashing #!EL #!N #!F-adobe-times-medium-i-normal--18* #!N