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::CompType mtype(sizeof(Class));
mtype.insertMember("MD", HOFFSET(Class, dMD), datatype);
H5::DataSet dataset = 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 b from an
array of the struct
typedef struct s1_t {
int a;
float b;
double c;
} 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::CompType mtype(sizeof(Class));
mtype.insertMember("MD", HOFFSET(Class, dMD), datatype);
H5::DataSet dataset = 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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___________________________________________________________________________
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
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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]
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