CODEWITHSUNDEEP
hdf5hdfhdfql
Mr Squid
Mr Squid

Reputation: 1286

HDFql Adding Data to Existing Dataset

I want to create a HDF5 file in C++ and dynamically add data to a dataset contained in that file. I have been having some trouble getting this work however, with this minimal example as my current best attempt (based mainly on an answer by SOG):

#include <stdio.h>
#include <HDFql.hpp>

int main (int argc, const char * argv[]) {
    char script[1024];

    //Create HDF5 file
    HDFql::execute("CREATE TRUNCATE FILE /tmp/test.h5");
    HDFql::execute("USE FILE /tmp/test.h5");

    //Generate some arbitrary data
    int data_size = 10;
    int data[data_size];
    for (int i=0; i<data_size; i++) {data[i]=i+data_size;}

    //Create a dataset "dset"
    HDFql::execute("CREATE CHUNKED DATASET dset AS INT(UNLIMITED)");
    //In the loop, add one element to dset on each iteration
    for(int i=0; i<10; i++)
    {
        HDFql::execute("ALTER DIMENSION dset TO (+1)");
        sprintf(script, "INSERT INTO dset(-1:1:1:1) VALUES(%d)", i);
        HDFql::execute(script);
    }
    //Add an array of values to dset
    sprintf(script, "ALTER DIMENSION dset TO (%d)", data_size);
    HDFql::execute(script);
    sprintf(script, "INSERT INTO dset(-1:1:1:1) VALUES(%d)", data_size);
    HDFql::execute(script);

    //Read all values in dset and print to console
    HDFql::execute("SELECT FROM dset");
    int cnt=0;
    while(HDFql::cursorNext(NULL) == HDFQL_SUCCESS)
    {
        printf("Value at %d: %d\n", cnt, *HDFql::cursorGetInt(NULL));
        cnt++;
    }

    HDFql::execute("CLOSE FILE");
}

I would expect the output of the console to be:

Value at 0: 0
Value at 1: 1
Value at 2: 2
...
Value at 19: 19

Instead the output is:

Value at 0: 10

And indeed, inspecting the HDF5 file shows that it contains only one value, 10. So what is wrong with my code and why? Also, a short explanation of the hyperslab (which I am using quite blindly here) or a link to documentation explaining it would be very appreciated.

Many thanks!

Edit

Here is a working code example based on the answer by @SOG:

#include <stdio.h>
#include <HDFql.hpp>

int main (int argc, const char * argv[]) {
    char script[1024];

    HDFql::execute("CREATE TRUNCATE FILE /tmp/test.h5");
    HDFql::execute("USE FILE /tmp/test.h5");

    int data_size = 10;
    int data[data_size];
    for (int i=0; i<data_size; i++) {data[i]=i+data_size;}

    HDFql::execute("CREATE CHUNKED DATASET dset AS INT(UNLIMITED)");
    for(int i=0; i<10; i++)
    {
        if(i>0) {HDFql::execute("ALTER DIMENSION dset TO +1");}
        sprintf(script, "INSERT INTO dset(-1:1:1:1) VALUES(%d)", i);
        HDFql::execute(script);
    }
    sprintf(script, "ALTER DIMENSION dset TO +%d", data_size);
    HDFql::execute(script);
    sprintf(script, "INSERT INTO dset(-%d:1:1:%d) VALUES FROM MEMORY %d",
            data_size, data_size, HDFql::variableTransientRegister(data));
    HDFql::execute(script);


    int cnt=0;
    HDFql::execute("SELECT FROM dset");
    while(HDFql::cursorNext(NULL) == HDFQL_SUCCESS)
    {
        printf("Value at %d: %d\n", cnt, *HDFql::cursorGetInt(NULL));
        cnt++;
    }

    HDFql::execute("CLOSE FILE");
}

Upvotes: 1

Views: 273

Answers (1)

SOG
SOG

Reputation: 912

According to HDFql release notes, operation ALTER DIMENSION has changed syntax in version 2.1.0 (i.e. the operation does not require parenthesis to surround dimensions anymore).

Therefore, change your code to:

HDFql::execute("ALTER DIMENSION dset TO +1");

Additional information about this operation as well as hyperslabs can be found in HDFql reference manual.

Upvotes: 1

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