On Jul 19, 2010, at 8:56 PM, Ethan Dreyfuss wrote:
> I think your problem might be the H5S_ALL in your H5DWrite.
Yes, I think that's part of the issue. I also think Mihail wants to
use H5Dset_extent() to make the dataset's dataspace larger on each pass through
the loop.
Quincey
> The docs say the following for specifying H5S_ALL for memspace and a valid
> dataspace id for file space:
>
> The file dataset's dataspace is used for the memory dataspace and the
> selection specified with file_space_id specifies the selection within it. The
> combination of the file dataset's dataspace and the selection from
> file_space_id is used for memory also.
>
> Which means that you're selecting elements at an offset of more than one into
> your one element array ii.
>
> Cheers,
> Ethan
>
> On Mon, Jul 19, 2010 at 4:32 PM, Schoolov, Mihail Y CIV SPAWARSYSCEN-PACIFIC,
> 56540 <[email protected]> wrote:
> I'm trying to write data to a dataset consisting of a 1-by-4 array of
> integers, but I want to write the integers one-by-one, appending an integer
> to the existing dataset each time through the loop. I'm using a hyperslab to
> select where I am writing, and then writing the integer (four writes total).
> This simple example simulates the way I will (eventually) be writing more
> complex real-time data that is streaming in.
>
> Everything I've read so far indicates that the following code should work. Am
> I missing an obvious step? Why is only the first element being written
> correctly?
>
> Thanks in advance - I appreciate any feedback and am looking to learn from my
> mistakes.
>
>
>
> // Create file descriptor for HDF output file
> hid_t file = H5Fcreate("output.h5", H5F_ACC_TRUNC, H5P_DEFAULT,
> H5P_DEFAULT);
>
> hid_t dataset, datatype, dataspace;
>
> // Initial hyperslab selection will be the first element (0,0)
> hsize_t start[] = {0,0};
> hsize_t count[] = {1,1};
>
> // Make the dataset dimensions 1-by-4
> hsize_t dims[] = {1, 4};
>
> // Create the file dataspace
> dataspace = H5Screate_simple(2, dims, NULL);
>
> // Create the dataset
> dataset = H5Dcreate(file, "/dset", H5T_STD_I32LE, dataspace,
> H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
>
> // Create buffer
> int *ii = new int;
>
> for (int i = 0; i < 4; i++) {
> // Set value of buffer (first time is 15, then 16, etc)
> *ii = i+15;
>
> // Select 1-by-1 hyperslab to write to, starting at the first
> element (0,0)
> start[1] = i;
> H5Sselect_hyperslab(dataspace, H5S_SELECT_SET, start, NULL,
> count, NULL);
>
> // Write data
> H5Dwrite(dataset, H5T_STD_I32LE, H5S_ALL, dataspace,
> H5P_DEFAULT, ii);
> }
>
> // Clean up
> H5Dclose(dataset);
> H5Sclose(dataspace);
> H5Fclose(file);
>
> // I expect this to create the following 1-by-4 dataset of integer
> elements:
> //
> // | 15 | 16 | 17 | 18 |
> //
> // Instead, it only seems to write to the first element:
> //
> // | 15 | -1219428236 | 0 | 17 |
> //
> // In fact, even if skip the first element, and initially set start
> to {0, 1}, it still won't
> // let me write to any of the other elements:
> //
> // | 0 | -1219428236 | 0 | 17 |
> //
> // What is going on? FYI: I mostly followed the code written in the
> HDF User Guide
>
>
>
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