Patch for HDF5 block size recognition

[jurien]

Problem: HDF5 driver does not implement HDF chunk size detection. Simptoms: HDF5 is *very* slow on compressed files with chunksize != 1 line (default block size for HDF5 gdal driver)

I have modified the GDAL HDF5 driver to extract the chunk size and load it as the block size for the dataset.

Regards

[jurien]

patch to read chunksize from an HDF5 file and optimize reads

[warmerdam]

Mateusz,

As time permits please review and apply the patches. I am not aware autotests for HDF5. This should also be addressed as part of this effort.

[nowakpl]

To me it looks like the patch would lead to incorrect memory layout for border blocks.

[jurien]

@nowakpl: you mean if the blocksize is not a multiple of the imagesize? it is checked with at lines 304 and 308. I check for the size of the image and the boundaries of the block and keep the minimum of those. If that's not what you mean, please explain me what you meant so I can try and fix it.

Regards.

[jurien]

Hello,

1.5.3 is about to be released, has this patch been postponed?

Regards

[warmerdam]

Jurien,

I'm afraid this issue has fallen through the cracks. I'm not inclined to hold 1.5.3 back for this at this stage.

[antonio]

I'm massively using a modified version of the HDF5 driver (build as plugin) that includes the patch from jurien.

If this helps I can confirm that the patch works very well and also produces a good performances boost. Thanks jurien.

[jurien]

Hello,

I'm bumping this ticket. I would really appreciate if the patch gets on the trunk.

To antonio: would you care to share your modifications on the HDF5 patch?

Regards.

[warmerdam]

Jurien,

Could you provide a pointer to a file demonstrating the issue?

Chaitanya,

Could you review the patch, and apply if it works ok? Please try to add/extend autotest if there is a file utilizing this feature that is a reasonable size.

[antonio]

updated patch against r17717

[antonio]

Replying to jurien:

Hello,

I'm bumping this ticket. I would really appreciate if the patch gets on the trunk.

To antonio: would you care to share your modifications on the HDF5 patch?

Regards.

Hi jurien, I've just uploaded an updated version of your patch. It should fix the issue at image borders and it should also work a little better with non-chunked datasets. It is just an extract of my working code so please check it before applying.

[chaitanya]

Tested and applied the patch in trunk (r17802) and 1.6 branch (r17801).