Hi Aman,
the file type would need to be a compound type as well with a member
name equal to the member in the memory type. Then HDF5 can convert it.
An elementtype of float would not work, but something like
struct MemType { int a, b; };
struct FileType { int b; };
Then if you have an in-memory array of type MemType and dataset of type
FileType, it should just write the "b" component of the in-memory array
to the file.
Werner
On 22.07.2016 21:29, Aman Verma wrote:
Werner,
Thanks for responding. I understand what you’re saying and had tried
it before. During dataset creation, I replaced mtype (Class’ type)
with mElementType (let’s say float). This leads to runtime errors.
H5::CompTypemtype(sizeof(Class));
mtype.insertMember("MD", HOFFSET(Class, dMD), datatype);
H5::DataSetdataset = solution.createDataSet( "/Well", mElementType,
dataspace, ds_creatplist );
dataset.write( ObjectArray, mtype );
Further on, during the dataset write, I now substitute:
dataset.write( ObjectArray, mElementType );
This too leads to some complaining. However, the file is written out
but with junk/wrong values. I am not surprised at this behavior given
what I’m doing. However, I wonder if there is a way to release the
unused space.
Again, for simplicity, let’s say I only want to write out the element
bfrom an array of the struct
typedefstructs1_t {
int a;
float b;
doublec;
} s1_t[LENGTH];
How can I achieve this without doing:
s1_tid = H5Tcreate (H5T_COMPOUND, sizeof(s1_t));
which leads to the file size being on the order of sizeof(s1_t)instead
of sizeof(float))?
Appreciate your time.
Aman
*From:*Hdf-forum [mailto:[email protected]] *On
Behalf Of *Werner Benger
*Sent:* Friday, July 22, 2016 9:58 AM
*To:* [email protected]
*Subject:* Re: [Hdf-forum] [Ext] Re: Writing subset of compound datatype
Hi Aman,
no, you don't copy anything. You reference your full data structure
and describe it with the complete memory layout of your data
structure, but in the file you use a different data type. Currently
you are using "mtype" in both the creation of the dataset and when
writing the data, so in file you get the same as in memory. But you
dont want that, you want to create a dataset that contains only a part
of your data structure, so during data set creation time you would use
a different type, not "mtype".
Werner
On 22.07.2016 16:07, Aman Verma wrote:
Hi Werner,
I guess what you’re implying is that I copy the components being
written to file (Element belonging to ObjectArray[i]) to a
different, more appropriate datatype such as an array:
ElementTemp[i]. However I want to avoid doing this copying at
every time step. There also doesn’t seem a way to make a reference
to this data, else I could just use that to write. What am I
missing here?
Aman
*From:*Hdf-forum [mailto:[email protected]] *On
Behalf Of *Werner Benger
*Sent:* Friday, July 22, 2016 7:58 AM
*To:* [email protected]
<mailto:[email protected]>
*Subject:* [Ext] Re: [Hdf-forum] Writing subset of compound datatype
Hi,
you probably want a different datatype in the file than in
memory, i.e. in memory you want a datatype that describes the
entire class, but for the file type one that only refers to the
components written.
Werner
On 22.07.2016 00:22, Aman Verma wrote:
I want to write, in a single line, the elements:
ObjectArray[i].Element (0<=i<n) without having to copy the
elements into a separate array altogether.
Using CompType and insertMember, I am writing just a subset
(including Element) of an array of a compound datatype
ObjectArray (a class/object in my case).
H5::CompTypemtype(sizeof(Class));
mtype.insertMember("MD", HOFFSET(Class, dMD), datatype);
H5::DataSetdataset = solution.createDataSet( "/Well", mtype,
dataspace, ds_creatplist );
dataset.write( ObjectArray, mtype );
This works fine. However, not unexpectedly, since I am
defining the CompType with the size of the whole class
(Class), while writing out only a subset (Element), my .h5
file is bigger (sizeof(Class)) than it should be
(sizeof(Element)). I am already using compression. Is there a
way to ‘delete’ this unused space? Or is there a better way to
do what I’m trying to achieve? Is using hyperslab the right
answer?
Thanks
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2019 Digital Media Center, Baton Rouge, Louisiana 70803
Tel.: +1 225 578 4809 Fax.: +1 225 578-5362
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___________________________________________________________________________
Dr. Werner Benger Visualization Research
Center for Computation & Technology at Louisiana State University (CCT/LSU)
2019 Digital Media Center, Baton Rouge, Louisiana 70803
Tel.: +1 225 578 4809 Fax.: +1 225 578-5362
_______________________________________________
Hdf-forum is for HDF software users discussion.
[email protected]
http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org
Twitter: https://twitter.com/hdf5
--
___________________________________________________________________________
Dr. Werner Benger Visualization Research
Center for Computation & Technology at Louisiana State University (CCT/LSU)
2019 Digital Media Center, Baton Rouge, Louisiana 70803
Tel.: +1 225 578 4809 Fax.: +1 225 578-5362
_______________________________________________
Hdf-forum is for HDF software users discussion.
[email protected]
http://lists.hdfgroup.org/mailman/listinfo/hdf-forum_lists.hdfgroup.org
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