Databases
StackOverflow2013
Postsdbo
POjava why different memory usage for primitive versus object array in 2D
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POjava why different memory usage for primitive versus object array in 2D
    primarykey
    data
    text
    <p>Relevant code</p> <pre><code>int row = 100000; int col = 18; Object[][] objectArray = new Object[row][1]; int[][] intArray = new int[row][1]; System.out.println("Size of objectArray = " + net.sourceforge.sizeof.SizeOf.deepSizeOf(objectArray) + " bytes"); System.out.println("Size of intArray = " + net.sourceforge.sizeof.SizeOf.deepSizeOf(intArray) + " bytes"); Object[][] objectMatrix = new Object[row][col]; int[][] intMatrix = new int[row][col]; System.out.println("Size of objectMatrix = " + net.sourceforge.sizeof.SizeOf.deepSizeOf(objectMatrix) + " bytes"); System.out.println("Size of intMatrix = " + net.sourceforge.sizeof.SizeOf.deepSizeOf(intMatrix) + " bytes"); </code></pre> <p>Relevant output</p> <pre><code>Size of objectArray = 4000024 bytes Size of intArray = 4000024 bytes Size of objectMatrix = 17600024 bytes Size of intMatrix = 10400024 bytes </code></pre> <p>If instead of 1D (number of cols=1), I have 2D (number of cols > 1), the object matrix takes more space.</p> <p>Can someone explain the reason?</p> <p>Edit: Added another case with just one row</p> <pre><code> int row = 1; int col = 2; Object[][] objectArray = new Object[row][1]; int[][] intArray = new int[row][1]; System.out.println("Size of objectArray = " + net.sourceforge.sizeof.SizeOf.deepSizeOf(objectArray) + " bytes"); System.out.println("Size of intArray = " + net.sourceforge.sizeof.SizeOf.deepSizeOf(intArray) + " bytes"); Object[][] objectMatrix = new Object[row][col]; int[][] intMatrix = new int[row][col]; System.out.println("Size of objectMatrix = " + net.sourceforge.sizeof.SizeOf.deepSizeOf(objectMatrix) + " bytes"); System.out.println("Size of intMatrix = " + net.sourceforge.sizeof.SizeOf.deepSizeOf(intMatrix) + " bytes"); </code></pre> <p>Output</p> <pre><code>Size of objectArray = 64 bytes Size of intArray = 64 bytes Size of objectMatrix = 72 bytes Size of intMatrix = 64 bytes </code></pre>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USSantosh Tiwari
    1. USSantosh Tiwari
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POjava why different memory usage for primitive versus object array in 2D
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POjava why different memory usage for primitive versus object array in 2D
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POjava why different memory usage for primitive versus object array in 2D
      1. UStemplatetypedef
      1. VTFavorite
    1. COI guess maybe an object array takes more space. (Dunno why this would be, but it's possible, depending on the internal implementation.)
      singulars
      1. POjava why different memory usage for primitive versus object array in 2D
      1. USHot Licks
    2. CO(And, of course, on a full 64-bit Java implementation, pointers are twice as big as ints.)
      singulars
      1. POjava why different memory usage for primitive versus object array in 2D
      1. USHot Licks
    3. CO(I have no idea how deepSizeOf works internally, but if it's somehow looking at allocations there's no guarantee that two identical objects occupy the same size allocations.)
      singulars
      1. POjava why different memory usage for primitive versus object array in 2D
      1. USHot Licks
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload