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<HTML><HEAD>
<TITLE>HDF5 Tutorial - Selecting Individual Points and Copying a Dataspace
</TITLE>
</HEAD>
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[ <A HREF="title.html"><I>HDF5 Tutorial Top</I></A> ]
<H1>
<BIG><BIG><BIG><FONT COLOR="#c101cd">Selecting Individual Points and Copying
a Dataspace</FONT>
</BIG></BIG></BIG></H1>
<hr noshade size=1>
<BODY>
<H2>Contents:</H2>
<UL>
<LI> <A HREF="#def">Description</A>
<LI> Programming Example
<UL>
<LI> <A HREF="#desc">Description</A>
<LI> <A HREF="#rem">Remarks</A>
<LI> <A HREF="#fc">File Contents</A>
</UL>
</UL>
<HR>
<A NAME="def">
<H2>Description</h2>
You can select independent points to read from or write to in a
dataspace by use of the <CODE>H5Sselect_elements</CODE> /
<CODE>h5sselect_elements_f</CODE> function.
<P>
The <CODE>H5Scopy</CODE> / <CODE>h5scopy_f</CODE> function allows
you to make an exact copy of a dataspace.
This can reduce the number of function calls needed when
selecting a dataspace.
<P>
<H2> Programming Example</H2>
<A NAME="desc">
<H3><U>Description</U></H3>
This example shows how to use <CODE>H5Sselect_elements</CODE> /
<CODE>h5sselect_elements_f</CODE>
to select individual points in a dataset and how to use
<CODE>H5Scopy</CODE> / <CODE>h5scopy_f</CODE>
to make a copy of a dataspace.
<UL>
[ <A HREF="examples/h5_copy.c">C example</A> ]
- <code>h5_copy.c</code><BR>
[ <A HREF="examples/selectele.f90">FORTRAN example</A> ]
- <code>selectele.f90</code><BR>
[ <A HREF="examples/java/Copy.java">Java example</A> ]
- <code>Copy.java</code>
</UL>
<B>NOTE:</B> To download a tar file of the examples, including a Makefile,
please go to the <A HREF="references.html">References</A> page.
<A NAME="rem">
<H3><U>Remarks</U></H3>
<UL>
<LI><CODE>H5Sselect_elements</CODE> / <CODE>h5sselect_elements_f</CODE>
selects array elements to be
included in the selection for a dataspace:
<P>
<I><B>C</B></I>:
<pre>
herr_t H5Sselect_elements (hid_t space_id, H5S_seloper_t operator,
size_t num_elements,
const hssize_t **coord )
</pre>
<P>
<I><B>FORTRAN</B></I>:
<pre>
h5sselect_elements_f (space_id, operator, num_elements, coord, hdferr)
space_id IN: INTEGER(HID_T)
operator IN: INTEGER
num_elements IN: INTEGER
coord IN: INTEGER(HSSIZE_T), DIMENSION(*,*)
hdferr OUT: INTEGER
</pre>
<P>
<UL>
<LI>The <I>space_id</I> parameter is the dataspace identifier.
<P>
<LI>The <I>operator</I> parameter can be set to one of the following values:
<dir><DL>
<dt><CODE>H5S_SELECT_SET</CODE> (<CODE>H5S_SELECT_SET_F</CODE> in FORTRAN)
<dd>Replace the existing selection with the parameters from this call.
Overlapping blocks are not supported with this operator.
<dt><CODE>H5S_SELECT_OR</CODE> (<CODE>H5S_SELECT_OR_F</CODE> in FORTRAN)
<dd>Add the new selection to the existing selection.
</DL></dir>
<P>
<LI>The <I>coord</I> array is a two-dimensional array of size
<code><em>NUMP</em> x <em>RANK</em></code> in C
(<code><em>RANK</em> x <em>NUMP</em></code> in FORTRAN)
where <code><em>NUMP</em></code> is the number of selected points
and <code><em>RANK</em></code> is the rank of the dataset.
Note that these coordinates are 0-based in C and 1-based in FORTRAN.
<p>
Consider the non-zero elements of the following array:
<pre>
0 59 0 53
0 0 0 0
0 0 1 0 </pre>
In C, the <em>coord</em> array selecting these points would be as follows:
<pre>
0 1
0 3
2 2 </pre>
While in FORTRAN, the <em>coord</em> array would be as follows:
<pre>
1 1 3
2 4 3 </pre>
<P>
<LI>In C, this function returns a non-negative value if successful and
a negative value otherwise. In FORTRAN, the value returned in <I>hdferr</I>
indicates whether it was successful (0) or not (-1).
</UL>
<P>
<LI><CODE>H5Scopy</CODE> / <CODE>h5scopy_f</CODE> creates an exact copy of a dataspace:
<P>
<I><B>C</B></I>:
<PRE>
hid_t H5Scopy (hid_t space_id)
</PRE>
<I><B>FORTRAN</B></I>:
<PRE>
h5scopy_f (space_id, new_space_id, hdferr)
space_id IN: INTEGER(HID_T)
new_space_id OUT: INTEGER(HID_T)
hdferr OUT: INTEGER
</PRE>
<P>
<UL>
<LI>The <I>space_id</I> parameter is the dataspace identifier to copy.
<P>
<LI>In C, the identifier to the dataspace's copy is returned if the
function is successful and a negative value is returned if not. In
FORTRAN, the new dataspace identifier is returned in <I>new_space_id</I>
and the return value is returned in <I>hdferr</I> ( 0 if successful and
-1 if not).
</UL>
</UL>
</UL>
<P>
<A NAME="fc">
<H3><U>File Contents</U></H3>
Following is the DDL for <I>copy1.h5</I> and <I>copy2.h5</I>, as viewed with
the following commands:<br>
<code>h5dump copy1.h5</code> <br>
<code>h5dump copy2.h5</code>
<P>
<HR>
<B><I><U>C</U></B></I>:<P>
<B>Fig. S.1a</B> <I><code>copy1.h5</code> in DDL</I>
<PRE>
HDF5 "copy1.h5" {
GROUP "/" {
DATASET "Copy1" {
DATATYPE { H5T_STD_I32BE }
DATASPACE { SIMPLE ( 3, 4 ) / ( 3, 4 ) }
DATA {
0, 59, 0, 53,
0, 0, 0, 0,
0, 0, 0, 0
}
}
}
}
</PRE>
<B>Fig. S.1b</B> <I><code>copy2.h5</code> in DDL</I>
<PRE>
HDF5 "copy2.h5" {
GROUP "/" {
DATASET "Copy2" {
DATATYPE { H5T_STD_I32BE }
DATASPACE { SIMPLE ( 3, 4 ) / ( 3, 4 ) }
DATA {
1, 59, 1, 53,
1, 1, 1, 1,
1, 1, 1, 1
}
}
}
}
</PRE>
<HR>
<I><B><U>FORTRAN</U></B></I>:<P>
<B>Fig. S.2a</B> <I><code>copy1.h5</code> in DDL</I>
<PRE>
HDF5 "copy1.h5" {
GROUP "/" {
DATASET "Copy1" {
DATATYPE { H5T_STD_I32BE }
DATASPACE { SIMPLE ( 4, 3 ) / ( 4, 3 ) }
DATA {
0, 0, 0,
53, 0, 0,
0, 0, 0,
59, 0, 0
}
}
}
}
</PRE>
<B>Fig. S.2b</B> <I><code>copy2.h5</code> in DDL</I>
<PRE>
HDF5 "copy2.h5" {
GROUP "/" {
DATASET "Copy2" {
DATATYPE { H5T_STD_I32BE }
DATASPACE { SIMPLE ( 4, 3 ) / ( 4, 3 ) }
DATA {
1, 1, 1,
53, 1, 1,
1, 1, 1,
59, 1, 1
}
}
}
}
</PRE>
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<BR> <H6>Last Modified: March 16, 2001</H6><BR>
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