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| author | Frank Baker <fbaker@hdfgroup.org> | 2000-12-22 20:47:59 (GMT) |
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| committer | Frank Baker <fbaker@hdfgroup.org> | 2000-12-22 20:47:59 (GMT) |
| commit | c1d537db2b803d6908fe3f21f62c592c9cd2bf70 (patch) | |
| tree | 56a6cb7f00a6fbec3b071722df9705e744368073 /doc/html/Tutor/extend.html | |
| parent | d4c3773742b8dee426e7325fee4e8fc4015f2802 (diff) | |
| download | hdf5-c1d537db2b803d6908fe3f21f62c592c9cd2bf70.zip hdf5-c1d537db2b803d6908fe3f21f62c592c9cd2bf70.tar.gz hdf5-c1d537db2b803d6908fe3f21f62c592c9cd2bf70.tar.bz2 | |
[svn-r3196]
Purpose:
Adding Tutorial to development branch (R 1.4)
Platforms tested:
IE 5
Diffstat (limited to 'doc/html/Tutor/extend.html')
| -rw-r--r-- | doc/html/Tutor/extend.html | 314 |
1 files changed, 314 insertions, 0 deletions
diff --git a/doc/html/Tutor/extend.html b/doc/html/Tutor/extend.html new file mode 100644 index 0000000..03b5972 --- /dev/null +++ b/doc/html/Tutor/extend.html @@ -0,0 +1,314 @@ +<HTML><HEAD> +<TITLE>HDF5 Tutorial - Chunking and Extendible Datasets +</TITLE> +</HEAD> + +<body bgcolor="#ffffff"> + +<!-- BEGIN MAIN BODY --> + +<A HREF="http://www.ncsa.uiuc.edu/"><img border=0 +src="http://www.ncsa.uiuc.edu/Images/NCSAhome/footerlogo.gif" +width=78 height=27 alt="NCSA"><P></A> + + [ <A HREF="title.html"><I>HDF5 Tutorial Top</I></A> ] +<H1> +<BIG><BIG><BIG><FONT COLOR="#c101cd">Chunking and Extendible Datasets</FONT> +</BIG></BIG></BIG></H1> + +<hr noshade size=1> + +<BODY> +<H2>Contents:</H2> +<UL> + <LI><A HREF="#def">Creating an Extendible Dataset</A> + <LI>Programming Example +<UL> + <LI> <A HREF="#desc">Description</A> + <LI> <A HREF="#rem">Remarks</A> +<!-- + <LI> <A HREF="#fc">File Contents</A> + <LI> <A HREF="#ddl">Dataset Definition in DDL</A> +--> +</UL> +</UL> +<HR> +<A NAME="def"> +<H2>Creating an Extendible Dataset</H2> +An extendible dataset is one whose dimensions can grow. In HDF5, it is possible to define a dataset to have certain initial dimensions, then later +to increase the size of any of the initial dimensions. +<P> +HDF5 requires you to use chunking in order to define extendible datasets. Chunking makes it possible to extend datasets efficiently, without +having to reorganize storage excessively. +<P> +The following operations are required in order to write an extendible dataset: +<OL> + <LI>Declare the dataspace of the dataset to have unlimited dimensions for all dimensions that might eventually be extended. + <LI>Set dataset creation properties to enable chunking and create a dataset. + <LI>Extend the size of the dataset. +</OL> +<H2> Programming Example</H2> +<A NAME="desc"> +<H3><U>Description</U></H3> +This example shows how to create a 3 x 3 extendible dataset, write to that +dataset, extend the dataset to 10x3, and write to the dataset again. +[<A HREF="examples/h5_extend.c">Download h5_extend.c</A>] +<PRE> + +/************************************************************** + * + * This example shows how to work with extendible datasets. + * In the current version of the library a dataset MUST be + * chunked in order to be extendible. + * + * This example is derived from the h5_extend_write.c and + * h5_read_chunk.c examples that are in the "Introduction + * to HDF5". + * + *************************************************************/ + +#include "hdf5.h" + +#define FILE "ext.h5" +#define DATASETNAME "ExtendibleArray" +#define RANK 2 + +int +main (void) +{ + hid_t file; /* handles */ + hid_t dataspace, dataset; + hid_t filespace; + hid_t cparms; + hid_t memspace; + + hsize_t dims[2] = { 3, 3}; /* dataset dimensions + at creation time */ + hsize_t dims1[2] = { 3, 3}; /* data1 dimensions */ + hsize_t dims2[2] = { 7, 1}; /* data2 dimensions */ + + hsize_t maxdims[2] = {H5S_UNLIMITED, H5S_UNLIMITED}; + hsize_t size[2]; + hssize_t offset[2]; + hsize_t i,j; + herr_t status, status_n; + int data1[3][3] = { {1, 1, 1}, /* data to write */ + {1, 1, 1}, + {1, 1, 1} }; + + int data2[7] = { 2, 2, 2, 2, 2, 2, 2}; + + /* Variables used in reading data back */ + hsize_t chunk_dims[2] ={2, 5}; + hsize_t chunk_dimsr[2]; + hsize_t dimsr[2]; + int data_out[10][3]; + int rank, rank_chunk; + + /* Create the data space with unlimited dimensions. */ + dataspace = H5Screate_simple (RANK, dims, maxdims); + + /* Create a new file. If file exists its contents will be overwritten. */ + file = H5Fcreate (FILE, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT); + + /* Modify dataset creation properties, i.e. enable chunking */ + cparms = H5Pcreate (H5P_DATASET_CREATE); + status = H5Pset_chunk ( cparms, RANK, chunk_dims); + + /* Create a new dataset within the file using cparms + creation properties. */ + dataset = H5Dcreate (file, DATASETNAME, H5T_NATIVE_INT, dataspace, + cparms); + + /* Extend the dataset. This call assures that dataset is 3 x 3.*/ + size[0] = 3; + size[1] = 3; + status = H5Dextend (dataset, size); + + /* Select a hyperslab */ + filespace = H5Dget_space (dataset); + offset[0] = 0; + offset[1] = 0; + status = H5Sselect_hyperslab (filespace, H5S_SELECT_SET, offset, NULL, + dims1, NULL); + + /* Write the data to the hyperslab */ + status = H5Dwrite (dataset, H5T_NATIVE_INT, dataspace, filespace, + H5P_DEFAULT, data1); + + /* Extend the dataset. Dataset becomes 10 x 3 */ + dims[0] = dims1[0] + dims2[0]; + size[0] = dims[0]; + size[1] = dims[1]; + status = H5Dextend (dataset, size); + + /* Select a hyperslab */ + filespace = H5Dget_space (dataset); + offset[0] = 3; + offset[1] = 0; + status = H5Sselect_hyperslab (filespace, H5S_SELECT_SET, offset, NULL, + dims2, NULL); + + /* Define memory space */ + dataspace = H5Screate_simple (RANK, dims2, NULL); + + /* Write the data to the hyperslab */ + status = H5Dwrite (dataset, H5T_NATIVE_INT, dataspace, filespace, + H5P_DEFAULT, data2); + + /* Close resources */ + status = H5Dclose (dataset); + status = H5Sclose (dataspace); + status = H5Sclose (filespace); + status = H5Fclose (file); + +/**************************************************************** + Read the data back + ***************************************************************/ + + file = H5Fopen (FILE, H5F_ACC_RDONLY, H5P_DEFAULT); + dataset = H5Dopen (file, DATASETNAME); + filespace = H5Dget_space (dataset); + rank = H5Sget_simple_extent_ndims (filespace); + status_n = H5Sget_simple_extent_dims (filespace, dimsr, NULL); + + cparms = H5Dget_create_plist (dataset); + if (H5D_CHUNKED == H5Pget_layout (cparms)) + { + rank_chunk = H5Pget_chunk (cparms, 2, chunk_dimsr); + } + + memspace = H5Screate_simple (rank,dimsr,NULL); + status = H5Dread (dataset, H5T_NATIVE_INT, memspace, filespace, + H5P_DEFAULT, data_out); + printf("\n"); + printf("Dataset: \n"); + for (j = 0; j < dimsr[0]; j++) + { + for (i = 0; i < dimsr[1]; i++) + printf("%d ", data_out[j][i]); + printf("\n"); + } + + status = H5Pclose (cparms); + status = H5Dclose (dataset); + status = H5Sclose (filespace); + status = H5Sclose (memspace); + status = H5Fclose (file); +} ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ +</PRE> + +<A NAME="rem"> +<H3><U>Remarks</U></H3> +<P> +<UL> +<LI>The function H5Pcreate creates a new property as an instance of + a property list. The signature of this function is as follows: +<PRE> + hid_t H5Pcreate ( H5P_class_t type ) +</PRE> +<UL> +<LI>The parameter <I>type</I> is the type of property list to create.<BR> + The class types are: H5P_FILE_CREATE, H5P_FILE_ACCESS, H5P_DATASET_CREATE, + H5P_DATASET_XFER, and H5P_MOUNT +</UL> +<P> +<LI>The function H5Pset_chunk sets the size of the chunks used + to store a chunked layout dataset. + The signature of this function is as follows: +<PRE> + herr_t H5Pset_chunk ( hid_t plist, int ndims, const hsize_t * dim ) +</PRE> +<UL> +<LI>The first parameter, <I>plist</I>, is the identifier for the property + list to query. +<LI>The second parameter, <I>ndims</I>, is the number of dimensions of + each chunk. +<LI>The third parameter, <I>dim</I>, is an array containing the size of + each chunk. +</UL> +<P> +A non-negative value is returned if successful; otherwise a negative +value is returned. +<P> +<LI>The function H5Dextend extends a dataset that has an unlimited + dimension. The signature is as follows: +<PRE> + herr_t H5Dextend ( hid_t dataset_id, const hsize_t * size ) +</PRE> +<UL> +<LI>The first parameter, <I>dataset_id</I>, is the identifier of + the dataset. +<LI>The second parater, <I>size</I>, is an array containing the + new magnitude of each dimension. +</UL> +<P> +This function returns a non-negative value if successful; otherwise +it returns a negative value. +<P> +<LI>The H5Dget_create_plist function returns an identifier for a +copy of the dataset creation property list for a dataset. +<P> +<LI>The H5Pget_layout function returns the layout of the raw data for a +dataset. Valid types are H5D_COMPACT, H5D_CONTIGUOUS, and H5D_CHUNKED. +<P> +<LI>The H5Pget_chunk function retrieves the size of chunks for the +raw data of a chunked layout dataset. +The signature of this function is: +<PRE> + int H5Pget_chunk ( hid_t plist, int max_ndims, hsize_t * dims ) +</PRE> +<UL> +<LI>The first parameter, <I>plist</I>, is the identifier of the + property list to query. +<LI>The second parameter, <I>max_ndims</I>, is the size of the <I>dims</I> + array. +<LI>The third parameter, <I>dims</I>, is the array to store the chunk + dimensions +</UL> +<P> +<LI>The H5Pclose function terminates access to a property list. + The signature of this function is: +<PRE> + herr_t H5Pclose ( hid_t plist ) +</PRE> +where <I>plist</I> is the identifier of the property list to terminate +access to. +</UL> + + +<!-- +<A NAME="fc"> +<H3><U>File Contents</U></H3> +--> + + + + + +<!-- BEGIN FOOTER INFO --> + +<P><hr noshade size=1> +<font face="arial,helvetica" size="-1"> + <a href="http://www.ncsa.uiuc.edu/"><img border=0 + src="http://www.ncsa.uiuc.edu/Images/NCSAhome/footerlogo.gif" + width=78 height=27 alt="NCSA"><br> + The National Center for Supercomputing Applications</A><br> + <a href="http://www.uiuc.edu/">University of Illinois + at Urbana-Champaign</a><br> + <br> +<!-- <A HREF="helpdesk.mail.html"> --> +<A HREF="mailto:hdfhelp@ncsa.uiuc.edu"> +hdfhelp@ncsa.uiuc.edu</A> +<BR> <H6>Last Modified: August 27, 1999</H6><BR> +<!-- modified by Barbara Jones - bljones@ncsa.uiuc.edu --> +</FONT> +<BR> +<!-- <A HREF="mailto:hdfhelp@ncsa.uiuc.edu"> --> + +</BODY> +</HTML> + + + |