What is the best way to use QDataStream or QFile

[lni]

Hi,

I have a large binary file consisting 3000x3000x2000 floating data points (around 67G in size). For each interval of 2000, I need to read one float value. So in total I need to read 3000x3000 points. What is the fastest way to read it?

I did the following way and it takes a decade to read it out.

QFile file( ... );
QDataStream stream( &file );
 
qint64 pos( 0);
char data[ 4 ];
for ( int ix = 0; ix < 3000; ix++ ) {
  for ( int iy = 0; iy < 3000; iy++ ) {
    stream.device()->seek( pos );
    stream.readRawData( data, 4 );
    ...
    pos += 2000;
  }
}

QFile file( ... );
QDataStream stream( &file );

qint64 pos( 0);
char data[ 4 ];
for ( int ix = 0; ix < 3000; ix++ ) {
  for ( int iy = 0; iy < 3000; iy++ ) {
    stream.device()->seek( pos );
    stream.readRawData( data, 4 );
    ...
    pos += 2000;
  }
}

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