HDF5 重新缩放数据集最大维度

Question

我已经创建了一个带有分块布局的数据集，我已经确定了数据集的最大大小

DataSpace *dataspace = new DataSpace (2, dims, maxdims)//maxdims equal to dims
// Modify dataset creation property to enable chunking
DSetCreatPropList prop;
prop.setChunk(2, chunk_dims);

然后我在里面记录了一些数据。最近我需要调整这个数据集的大小，但是新的大小超过了我在开始时确定的最大大小，每次我尝试调整数据集的大小都会导致异常

dataset->extend(new_size); //New size 

有没有办法在不丢失记录数据的情况下扩展数据集的最大维度。如果没有，有没有办法用另一个包含我的数据并使用新的最大大小覆盖数据集？

Answer 1

选项 ::extend() 仅适用于可扩展数据集 (link)。

如果创建的数据集具有最大大小，则无法将其更改为可扩展的数据集。您必须将内容复制到创建为无限制的新数据集。

这里有一个来自 hdf 网站 (link) 的示例。

/*
 *   This example shows how to work with extendible dataset.
 *   In the current version of the library dataset MUST be
 *   chunked.
 */
#ifdef OLD_HEADER_FILENAME
#include <iostream.h>
#else
#include <iostream>
#endif
#include <string>
#ifndef H5_NO_NAMESPACE
#ifndef H5_NO_STD
    using std::cout;
    using std::endl;
#endif  // H5_NO_STD
#endif
#include "H5Cpp.h"
#ifndef H5_NO_NAMESPACE
    using namespace H5;
#endif
const H5std_string FILE_NAME( "SDSextendible.h5" );
const H5std_string DATASET_NAME( "ExtendibleArray" );
const int      NX = 10;
const int      NY = 5;
const int      RANK = 2;
int main (void)
{
   //Try block to detect exceptions raised by any of the calls inside it
   try
   {
      /*
       * Turn off the auto-printing when failure occurs so that we can
       * handle the errors appropriately
       */
      Exception::dontPrint();

      //Create the data space with unlimited dimensions.
      hsize_t      dims[2]  = { 3, 3};  // dataset dimensions at creation
      hsize_t      maxdims[2] = {H5S_UNLIMITED, H5S_UNLIMITED};
      DataSpace mspace1( RANK, dims, maxdims);

      //Create a new file. If file exists its contents will be overwritten.
      H5File file( FILE_NAME, H5F_ACC_TRUNC );

      //Modify dataset creation properties, i.e. enable chunking.          
      DSetCreatPropList cparms;
      hsize_t      chunk_dims[2] ={2, 5};
      cparms.setChunk( RANK, chunk_dims );

      //Set fill value for the dataset          
      int fill_val = 0;
      cparms.setFillValue( PredType::NATIVE_INT, &fill_val);

      //Create a new dataset within the file using cparms creation properties.
      DataSet dataset = file.createDataSet( DATASET_NAME, PredType::NATIVE_INT, mspace1, cparms);

      //Extend the dataset. This call assures that dataset is at least 3 x 3.
      hsize_t      size[2];
      size[0]   = 3;
      size[1]   = 3;
      dataset.extend( size );

      //Select a hyperslab.
      DataSpace fspace1 = dataset.getSpace ();
      hsize_t     offset[2];
      offset[0] = 0;
      offset[1] = 0;
      hsize_t      dims1[2] = { 3, 3};            /* data1 dimensions */
      fspace1.selectHyperslab( H5S_SELECT_SET, dims1, offset );

      //Write the data to the hyperslab.          
      int       data1[3][3] = { {1, 1, 1},       /* data to write */
                {1, 1, 1},
                {1, 1, 1} };
      dataset.write( data1, PredType::NATIVE_INT, mspace1, fspace1 );

      //Extend the dataset. Dataset becomes 10 x 3.           
      hsize_t   dims2[2] = { 7, 1};            /* data2 dimensions */
      dims[0]   = dims1[0] + dims2[0];
      size[0]   = dims[0];
      size[1]   = dims[1];
      dataset.extend( size );

      //Select a hyperslab.         
      DataSpace fspace2 = dataset.getSpace ();
      offset[0] = 3;
      offset[1] = 0;
      fspace2.selectHyperslab( H5S_SELECT_SET, dims2, offset );

      //Define memory space
      DataSpace mspace2( RANK, dims2 );

      //Write the data to the hyperslab.
      int  data2[7]    = { 2, 2, 2, 2, 2, 2, 2};
      dataset.write( data2, PredType::NATIVE_INT, mspace2, fspace2 );

      //Extend the dataset. Dataset becomes 10 x 5.
      hsize_t   dims3[2] = { 2, 2};            /* data3 dimensions */
      dims[1]   = dims1[1] + dims3[1];
      size[0]   = dims[0];
      size[1]   = dims[1];
      dataset.extend( size );

      //Select a hyperslab          
      DataSpace fspace3 = dataset.getSpace ();
      offset[0] = 0;
      offset[1] = 3;
      fspace3.selectHyperslab( H5S_SELECT_SET, dims3, offset );

      //Define memory space.
      DataSpace mspace3( RANK, dims3 );

      //Write the data to the hyperslab.          
      int         data3[2][2] = { {3, 3}, {3, 3} };
      dataset.write( data3, PredType::NATIVE_INT, mspace3, fspace3 );

      //Read the data from this dataset and display it.          
      int i, j;
      int data_out[NX][NY];
      for (i = 0; i < NX; i++)
      {
         for (j = 0; j < NY; j++)
            data_out[i][j] = 0;
      }
      dataset.read( data_out, PredType::NATIVE_INT );
      /*
       * Resulting dataset
       *
       *     1 1 1 3 3
       *     1 1 1 3 3
       *     1 1 1 0 0
       *     2 0 0 0 0
       *     2 0 0 0 0
       *     2 0 0 0 0
       *     2 0 0 0 0
       *     2 0 0 0 0
       *     2 0 0 0 0
       *     2 0 0 0 0
       */

      //Display the result.          
      for (i=0; i < NX; i++)
      {
          for(j=0; j < NY; j++)
             cout << data_out[i][j] << "  ";
          cout << endl;
      }
   }  // end of try block
   // catch failure caused by the H5File operations
   catch( FileIException error )
   {
      error.printError();
      return -1;
   }
   // catch failure caused by the DataSet operations
   catch( DataSetIException error )
   {
      error.printError();
      return -1;
   }
   // catch failure caused by the DataSpace operations
   catch( DataSpaceIException error )
   {
      error.printError();
      return -1;
   }
   // catch failure caused by the DataSpace operations
   catch( DataTypeIException error )
   {
      error.printError();
      return -1;
   }
   return 0;
}