mirror of
https://github.com/HDFGroup/hdf5.git
synced 2024-11-21 01:04:10 +08:00
ed7d456e51
Tested platform: Kagiso only since it is only a comment block change. If it works in one machine, it should work in all, I hope. Still need to check the parallel build on copper.
327 lines
13 KiB
C
327 lines
13 KiB
C
/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
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* Copyright by The HDF Group. *
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* Copyright by the Board of Trustees of the University of Illinois. *
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* All rights reserved. *
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* *
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* This file is part of HDF5. The full HDF5 copyright notice, including *
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* terms governing use, modification, and redistribution, is contained in *
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* the files COPYING and Copyright.html. COPYING can be found at the root *
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* of the source code distribution tree; Copyright.html can be found at the *
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* root level of an installed copy of the electronic HDF5 document set and *
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* is linked from the top-level documents page. It can also be found at *
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* http://hdfgroup.org/HDF5/doc/Copyright.html. If you do not have *
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* access to either file, you may request a copy from help@hdfgroup.org. *
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* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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/*
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* This program illustrates the usage of HDF5's implicit message sharing
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* feature, which can be used to save space when the same messages are
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* used many times in a file.
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*
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* This example creates a standard file using file creation property lists
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* to control which messages are shared. Messages that can be shared are
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* datatypes, dataspaces, attributes, fill values, and filter pipelines.
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*
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*/
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#include <stdlib.h>
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#include "hdf5.h"
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#define NUM_DATASETS 40
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const char* DSETNAME[] = {
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"dataset0", "dataset1",
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"dataset2", "dataset3",
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"dataset4", "dataset5",
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"dataset6", "dataset7",
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"dataset8", "dataset9",
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"dataset10", "dataset11",
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"dataset12", "dataset13",
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"dataset14", "dataset15",
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"dataset16", "dataset17",
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"dataset18", "dataset19",
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"dataset20", "dataset21",
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"dataset22", "dataset23",
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"dataset24", "dataset25",
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"dataset26", "dataset27",
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"dataset28", "dataset29",
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"dataset30", "dataset31",
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"dataset32", "dataset33",
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"dataset34", "dataset35",
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"dataset36", "dataset37",
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"dataset38", "dataset39",
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NULL
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};
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herr_t create_standard_file(const char *filename, hid_t fcpl);
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/*-------------------------------------------------------------------------
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* Function: main
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*
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* Purpose: Enables shared messages using File Creation Property Lists
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* and creates files using these settings.
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*
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*-------------------------------------------------------------------------
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*/
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int main(void)
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{
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hid_t fcpl_id;
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herr_t ret;
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/* Create a file creation property list */
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fcpl_id = H5Pcreate(H5P_FILE_CREATE);
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if(fcpl_id < 0) goto error;
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/* The file creation property list is the default list right now.
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* Create a file using it (this is the same as creating a file with
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* H5P_DEFAULT). Implicit shared messages will be disabled.
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*/
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ret = create_standard_file("default_file.h5", fcpl_id);
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if(ret < 0) goto error;
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/* There are five kinds of messages that can be shared: datatypes,
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* dataspaces, attributes, fill values, and filter pipelines.
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* Shared messages are stored in up to five "indexes," where each
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* index can contain one or more types of message. Using more indexes
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* will result in more overhead for sharing, but can also provide
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* more "tunability" and may affect caching performance.
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*/
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/* To begin with, use only one index. */
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ret = H5Pset_shared_mesg_nindexes(fcpl_id, 1);
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if(ret < 0) goto error;
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/* Each index has a "minimum message size" for a message of that
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* type to be shared. Since sharing a message creates some overhead,
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* this is to prevent this overhead for very small messages when little
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* space would be saved by sharing them anyway.
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* If the content of the file isn't known beforehand, it's probably best
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* to set the minimum size "high"; over 100 or 200 bytes. If the content
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* of the file is known, this value can be used to trade space saved for
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* performance lost. The smaller this value is, the more messages will
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* be shared, so the more overhead will be incurred.
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* This value is in bytes. A shared message involves about 30 bytes of
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* overhead. Note that even messages that are only written once will
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* require this overhead (since they "might" be shared in the future),
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* so setting the minimum size too low may result in a file actually growing
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* in size.
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* For this example case, we'll set the minimum sharing size to be small
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* since we know that every message the "standard" file uses will be
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* repeated many times.
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*/
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/* The other property that each index has is the kinds of messages that
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* it holds. For the simple case, we'll put every message that could be
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* shared in this single index.
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*/
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ret = H5Pset_shared_mesg_index(fcpl_id, 0, H5O_MESG_ALL_FLAG, 40);
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if(ret < 0) goto error;
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/* The other property that can be set for shared messages is the
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* list/B-tree cutoff for the indexes.
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* Each shared message index beins life as a simple list of messages
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* and becomes a B-tree when "too many" messages are written to it.
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* This keeps the indexes simple when only a few messages are shared,
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* but allows them to scale for many messages. If many messages are
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* deleted from the B-tree, it scales back down into a list.
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* A "resonable" setting for maximum list size and minimum btree size
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* depends on what kinds of messages will be stored in the file.
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* These numbers are the same for all indexes in a file.
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* We'll guess at some numbers, though we could just as easily have kept
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* the default values. The first value is the maximum list size, the
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* second the minimum B-tree size.
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*/
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ret = H5Pset_shared_mesg_phase_change(fcpl_id, 30, 20);
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if(ret < 0) goto error;
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/* Now create a file with this property list. After the FCPL is used,
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* everything is automatic; messages will be shared and this will be
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* completely transparent to the user. Even if the file is closed
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* and re-opened, this settings will be saved and applied to messages
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* written later.
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*/
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ret = create_standard_file("one_index_file.h5", fcpl_id);
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if(ret < 0) goto error;
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/* Now try some variations on this. The FCPL hasn't been closed, so
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* we don't need to re-create it.
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* For instance, if we set the index to only share very large
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* messages, none of the messages we write will qualify and the file
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* will be about the same size as a normal file (with just a little extra
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* overhead).
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*/
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ret = H5Pset_shared_mesg_index(fcpl_id, 0, H5O_MESG_ALL_FLAG, 1000);
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if(ret < 0) goto error;
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ret = create_standard_file("only_huge_mesgs_file.h5", fcpl_id);
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if(ret < 0) goto error;
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/* Or, suppose we only wanted to shared dataspaces and
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* attributes (which might make sense if we were going to use committed
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* datatypes). We could change the flags on the index:
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*/
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ret = H5Pset_shared_mesg_index(fcpl_id, 0, H5O_MESG_SDSPACE_FLAG | H5O_MESG_ATTR_FLAG, 40);
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if(ret < 0) goto error;
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ret = create_standard_file("only_dspaces_and_attrs_file.h5", fcpl_id);
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if(ret < 0) goto error;
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/* We could create a second index and put attributes in it to separate them
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* from datatypes and dataspaces (and then run some performance metrics to
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* see whether this improved caching performance).
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*/
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ret = H5Pset_shared_mesg_nindexes(fcpl_id, 2);
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if(ret < 0) goto error;
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ret = H5Pset_shared_mesg_index(fcpl_id, 0, H5O_MESG_DTYPE_FLAG | H5O_MESG_SDSPACE_FLAG, 40);
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if(ret < 0) goto error;
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ret = H5Pset_shared_mesg_index(fcpl_id, 1, H5O_MESG_ATTR_FLAG, 40);
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if(ret < 0) goto error;
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ret = create_standard_file("separate_indexes_file.h5", fcpl_id);
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if(ret < 0) goto error;
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/* We can try twiddling the "phase change" values and see what it does to
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* the file size. Since there's only a few different messages (two
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* datatypes, two dataspaces, and one attribute), using smaller lists will
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* save some space.
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*/
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ret = H5Pset_shared_mesg_nindexes(fcpl_id, 1);
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if(ret < 0) goto error;
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ret = H5Pset_shared_mesg_index(fcpl_id, 0, H5O_MESG_ALL_FLAG, 40);
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if(ret < 0) goto error;
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ret = H5Pset_shared_mesg_phase_change(fcpl_id, 5, 0);
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if(ret < 0) goto error;
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ret = create_standard_file("small_lists_file.h5", fcpl_id);
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if(ret < 0) goto error;
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/* Or we could create indexes that are never lists, but are created as
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* B-trees. We do this by setting the "maximum list size" to zero.
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*/
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ret = H5Pset_shared_mesg_phase_change(fcpl_id, 0, 0);
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if(ret < 0) goto error;
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ret = create_standard_file("btrees_file.h5", fcpl_id);
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if(ret < 0) goto error;
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/* Obviously there are a lot more permutations of these options possible.
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* Performance will often be a tradeoff of speed for space, but will
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* depend a great deal on the specific application. If performance is
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* important, the best thing to do is to play with these settings to find
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* the ones that work best for you.
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* Please let The HDF Group (help@hdfgroup.org) know what you find!
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*/
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/* Close the property list */
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ret = H5Pclose(fcpl_id);
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if(ret < 0) goto error;
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return 0;
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error:
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return -1;
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}
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/*-------------------------------------------------------------------------
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* Function: create_standard_file
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*
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* Purpose: A helper functon for the example. Creates an HDF5 file
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* with many repeated messages using the file creation
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* property list FCPL.
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*
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* This function only uses datatypes, dataspaces, and
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* attributes. Fill values and filter pipelines can also
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* be shared in the same way (i.e., by enabling sharing in
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* the FCPL and writing the same message more than once).
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*-------------------------------------------------------------------------
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*/
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herr_t
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create_standard_file(const char *filename, hid_t fcpl_id)
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{
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hid_t file_id=-1;
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hid_t type_id=-1, temp_type_id=-1;
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hsize_t dims[] = {10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
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hid_t space_id=-1;
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hid_t attr_type_id = -1;
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hid_t attr_space_id = -1;
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int attr_data[] = {1,2,3,4,5,6,7,8,9,0};
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hid_t dset_id=-1;
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hid_t attr_id=-1;
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int x;
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herr_t ret;
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/* Create the file */
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file_id = H5Fcreate(filename, H5F_ACC_TRUNC, fcpl_id, H5P_DEFAULT);
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if(file_id < 0) goto error;
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/* Create the datatype we'll be using. Generally, sharing messages
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* is most useful when the message is complex and takes more space on
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* disk, so this type will be an array type rather than an atomic type.
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* However, any type can be shared.
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*/
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temp_type_id = H5Tarray_create(H5T_NATIVE_INT, 10, dims, NULL);
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if(temp_type_id < 0) goto error;
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type_id = H5Tarray_create(temp_type_id, 10, dims, NULL);
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if(type_id < 0) goto error;
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ret = H5Tclose(temp_type_id);
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if(ret < 0) goto error;
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/* Create the dataspace we'll be using.
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* Again, create a more complex dataspace so that more space will
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* be saved when we share it.
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*/
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space_id = H5Screate_simple(10, dims, dims);
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if(space_id < 0) goto error;
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/* Create a datatype and dataspace for the attributes we'll be creating.
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* The datatype will be a single integer, and each attribute will hold
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* 10 integers.
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*/
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attr_type_id = H5Tcopy(H5T_NATIVE_INT);
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if(attr_type_id < 0) goto error;
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attr_space_id = H5Screate_simple(1, dims, dims);
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if(attr_space_id < 0) goto error;
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/* Begin using the messages many times. Do this by creating datasets
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* that use this datatype, dataspace, and have this attribute.
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*/
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for(x=0; x<NUM_DATASETS; ++x) {
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/* Create a dataset */
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dset_id = H5Dcreate(file_id, DSETNAME[x], type_id, space_id, H5P_DEFAULT);
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if(dset_id < 0) goto error;
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/* Create an attribute on the dataset */
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attr_id = H5Acreate(dset_id, "attr_name", attr_type_id, attr_space_id, H5P_DEFAULT);
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if(attr_id < 0) goto error;
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/* Write data to the attribute */
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ret = H5Awrite(attr_id, H5T_NATIVE_INT, attr_data);
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if(ret < 0) goto error;
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ret = H5Aclose(attr_id);
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if(ret < 0) goto error;
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ret = H5Dclose(dset_id);
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if(ret < 0) goto error;
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}
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/* Close all open IDs */
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ret = H5Tclose(attr_type_id);
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if(ret < 0) goto error;
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ret = H5Sclose(attr_space_id);
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if(ret < 0) goto error;
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ret = H5Tclose(type_id);
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if(ret < 0) goto error;
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ret = H5Sclose(space_id);
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if(ret < 0) goto error;
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ret = H5Fclose(file_id);
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if(ret < 0) goto error;
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return 0;
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error:
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return -1;
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}
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