EXPRESS/Binary Report

1
EXPRESS/Binary Report

• David Price
• ISO SC4 Vico Equense
• March 2006

2
Agenda

1. Introductions
2. Review of EXPRESS/Binary Project
3. Overview of EXPRESS/HDF5 mapping Version 0.2 and
   workshop comments
4. Issues and actions

3
EXPRESS/HDF5 Workshop Report

• ISO SC4 Vico Equense
• March 2006

4
Workshop

• Workshop hosted by HDF Group
• Workshop Dec 6-8, 2005
• Champaign, Illinois, USA
• STEP, ESA, commercial, EXPRESS/Binary and HDF 5
  developer attendees
• Agenda was
• Introduced HDF Group to EXPRESS language and STEP
  information models
• HDF developers provided overview of HDF 5
  Concepts and Structures
• Walkthrough of EXPRESS/HDF Mapping Draft 0.2
• Presentation by domain experts AP209 Analysis,
  STEP TAS, SINDA/G, Ship AP Analysis Needs
• Issues/requirements around APIs, programming
  languages, etc.

5
API Questions

• What are the requirements for APIs?
• Is there a need for an EXPRESS-specific HDF5 API?
• Is there a need for Higher-than-EXPRESS APIs (aka
  Business Object APIs)?
• Can we generate better performing, configured
  APIs?
• What layers of API/standard might be involved
• How we can align APIs or how the build upon each
  other?

6
HDF 5 Technical Comments (1)

• Files are identical no matter how written
• Should we use HDF attributes directly? They are
  in memory as soon as you open the file. They are
  not shared.
• Use Link concept for path names in documentation
• Use NATIVE datatypes in your appl and library
  will convert whatever is in the file to NATIVE
  for your platform, when using H5DWrite tell it
  source is NATIVE datatype
• Selection this is an area where we need work to
  understand how to use this

7
HDF 5 Technical Comments (2)

• Can we use fill values to deal with unset?
• Should variable length arrays be used for Bag,
  Set, List?
• Fixed length arrays should be used for Array
• Use H5Tget_native_type to find compound type in
  file and make in memory
• Combine shuffle with compression for even better
  results on space and IO time

8
HDF 5 Technical Comments (3)

• How he can have access to control block size
  physical block?
• HDF Chunking concept is aimed at this
• Parallel IO is also a way to do this
• HDF are looking at caching chunks and giving
  applications control of this
• Chunks are organized by B-trees but there is no
  user accessible algorithm for hashing at lower
  level
• User blocks can be added in front of HDF5 file,
  this can even be an executable program, PDF, etc.
  
• HDF Indexing project
• Adding an Index API
• Create Index
• Query returns dataspace with subset

9
Domain Model Discussions

• STEP TAS
• STEP TAS/HDF project 4-5 months started in Nov,
  Alain Fagot lead
• Why did they not use HDF enum for boolean and
  logical?
• Defined specific values for unset but may allow
  that to be set
• Is there value in storing Dictionary in HDF5?
• Does its use impact performance?
• H-P says NO They read the dictionary in as
  instance data in HDF
• AP209
• FEA needs HDF but perhaps PDM does not, should we
  look at a hybrid approach?
• Abaqus is working with HDF folks and does
  non-linear so may be interested in AP209 E2

10
Domain Model Discussions (2)

• Network Analysis
• Already working on using HDF as central database,
  storing FEA model at the moment
• Need higher level API to simulate database
  capabilities (i.e. index hashing for fast random
  access), C and F90 wrap HDF
• Next three months are critical for them in
  getting the database working
• HDF Group are working on an indexing capability
  and would like us to provide feedback
• Ron says he can give user guide for API and model
  for review
• Ship APs
• NSRP/PDES involvement
• AP227, 216, 218 -gt 209 somehow? ISE project uses
  XML to mediate between these and the AIM/ARM
  files
• At www.isetools.org they will deliver open-source
  STEP toolkits

11
Summary

• Many core issues on V0.2 addressed at the
  workshop
• The basic approach was flawed, V0.2 did not use
  enough of the HDF capability
• V0.3 will be an improvement and should allow
  better control of efficiency by the application
• http//www.exff.org/express_binary
• Prototyping will follow V0.3

12
Actions

• David Price Publish EXPRESS/HDF Mapping V0.3
  due March 24
• Mats Lindeblad Create New Work Item for June
  SC4 meeting
• David Price - contact Hans-Peter about linking a
  one-day workshop with the NASA/ESA PDE at the end
  of April (a day before Monday?)
• Keith Hunten plan session at Eng Analysis
  sessions at PDES, Inc. Offsite end of March
• David/Mats plan for technical work at June SC4
  meeting