Querying existence of a dataset

Hi All,

In the past, I've queried for existence of a dataset by attempting to
open it and, if that fails, assuming it did not exist.

First, is there a better/faster way?

Second, does anyone know of H5Dopen results in any actual disk I/O? Or,
is it simply interacting with metadata which is more than likely already
cached somewhere in memory?

Mark

···

--
Mark C. Miller, Lawrence Livermore National Laboratory
================!!LLNL BUSINESS ONLY!!================
miller86@llnl.gov urgent: miller86@pager.llnl.gov
T:8-6 (925)-423-5901 M/W/Th:7-12,2-7 (530)-753-851

Mark,

On (1) look at H5Lexists.

Can't help you on (2).

Scott

···

-----Original Message-----
From: hdf-forum-bounces@hdfgroup.org [mailto:hdf-forum-bounces@hdfgroup.org]
On Behalf Of Mark Miller
Sent: Thursday, February 04, 2010 2:36 PM
To: hdf-forum@hdfgroup.org
Subject: [Hdf-forum] Querying existence of a dataset

Hi All,

In the past, I've queried for existence of a dataset by attempting to
open it and, if that fails, assuming it did not exist.

First, is there a better/faster way?

Second, does anyone know of H5Dopen results in any actual disk I/O? Or,
is it simply interacting with metadata which is more than likely already
cached somewhere in memory?

Mark

--
Mark C. Miller, Lawrence Livermore National Laboratory
================!!LLNL BUSINESS ONLY!!================
miller86@llnl.gov urgent: miller86@pager.llnl.gov
T:8-6 (925)-423-5901 M/W/Th:7-12,2-7 (530)-753-851

_______________________________________________
Hdf-forum is for HDF software users discussion.
Hdf-forum@hdfgroup.org
http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org

This e-mail and any files transmitted with it may be proprietary and are intended solely for the use of the individual or entity to whom they are addressed. If you have received this e-mail in error please notify the sender.
Please note that any views or opinions presented in this e-mail are solely those of the author and do not necessarily represent those of ITT Corporation. The recipient should check this e-mail and any attachments for the presence of viruses. ITT accepts no liability for any damage caused by any virus transmitted by this e-mail.

Hi all,

Mark,

On (1) look at H5Lexists.

  Yes, plus we'll be adding a new routine 'H5Oexists_by_name' to the 1.8.5 release, to allow applications to check if a soft/external/user-defined link resolves to an object (and doesn't dangle).

Can't help you on (2).

  Yes, H5Dopen() can result in actual disk I/O, through attempting to read metadata about the dataset. If the dataset hasn't been created or opened since the application opened the file, the metadata will not be in the cache and will need to be read from the file.

  Quincey

···

On Feb 5, 2010, at 8:32 AM, Mitchell, Scott - IS wrote:

Scott

-----Original Message-----
From: hdf-forum-bounces@hdfgroup.org [mailto:hdf-forum-bounces@hdfgroup.org]
On Behalf Of Mark Miller
Sent: Thursday, February 04, 2010 2:36 PM
To: hdf-forum@hdfgroup.org
Subject: [Hdf-forum] Querying existence of a dataset

Hi All,

In the past, I've queried for existence of a dataset by attempting to
open it and, if that fails, assuming it did not exist.

First, is there a better/faster way?

Second, does anyone know of H5Dopen results in any actual disk I/O? Or,
is it simply interacting with metadata which is more than likely already
cached somewhere in memory?

Mark

--
Mark C. Miller, Lawrence Livermore National Laboratory
================!!LLNL BUSINESS ONLY!!================
miller86@llnl.gov urgent: miller86@pager.llnl.gov
T:8-6 (925)-423-5901 M/W/Th:7-12,2-7 (530)-753-851

_______________________________________________
Hdf-forum is for HDF software users discussion.
Hdf-forum@hdfgroup.org
http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org

This e-mail and any files transmitted with it may be proprietary and are intended solely for the use of the individual or entity to whom they are addressed. If you have received this e-mail in error please notify the sender.
Please note that any views or opinions presented in this e-mail are solely those of the author and do not necessarily represent those of ITT Corporation. The recipient should check this e-mail and any attachments for the presence of viruses. ITT accepts no liability for any damage caused by any virus transmitted by this e-mail.

_______________________________________________
Hdf-forum is for HDF software users discussion.
Hdf-forum@hdfgroup.org
http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org