Problem in Qvector initialization

[Alexanov]

Hi
I face to amazing problem !!!
can any body say me the reason of this reaction ?
when I wrote first line code , and debug my code this line allocated 15GB RAM but when replace number of array with scientific symbol this problem solved and my app work regularly .

//Qvector initialization 

1- QVector <QByteArray> vector(200000000);

// Replace number with scientific symbol
2- QVector <QByteArray> vector(2e8);

[jsulm]

@Alexanov Interesting. Just tested on Windows 7: works and consumes only 12MB RAM. Are you sure it is not something else in your app?
What is your OS, compiler and Qt version?

[koahnig]

@Alexanov

Check the size of the actual vector allocated in both cases.

qDebug() << "vector size " << vector.size();

The scientific representation is most likely not converted to the int number you are expecting.

[VRonin]

Tried with Qt 5.8 on Win7 and:

MSVC 2013 x64
Both versions allocate the correct amount of memory: (200000000 * sizeof(QByteArray)) + sizeof(QVector<QByteArray>) = (200000000*8)+8 = ~1.6GB

MSVC 2013 x32
Both versions allocate the correct amount of memory: (200000000 * sizeof(QByteArray)) + sizeof(QVector<QByteArray>)= (200000000*4)+4 = ~800MB

@koahnig said in Problem in Qvector initialization:

qDebug() << "vector size " << vector.size();

use capacity() instead of size() in this case.

What compiler/OS/architecture are you using?

[Alexanov]

@jsulm ,@koahnig ,@VRonin
:)) Oh Sorry Thanks alot for your answers, I saw code again , my number had 9 zero in it not 8 zero.
2000000000 (2e9) not 200000000 (2e8)!
And RAM allocation for 2e9 is correct:
(200000000*8)+8 = ~16GB