Databases
StackOverflow2013
Postsdbo
POCan someone explain to me what this GetCardinality method is doing?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POCan someone explain to me what this GetCardinality method is doing?
    primarykey
    data
    text
    <p>I've been looking into faceted search with Lucene.NET, I've found a brilliant example <a href="http://www.devatwork.nl/index.php/articles/lucenenet/faceted-search-and-drill-down-lucenenet/" rel="noreferrer">here</a> which explains a fair amount, apart from the fact that it completely overlooks the function which checks the cardinality of items in a bit array.</p> <p>Can anyone give me a run down of what it is doing? The main things I don't understand is why the bitsSetArray is created as it is, what it is used for and how all the if statements work in the for loop.</p> <p>This may be a big ask but I have to understand how this works before I can even think of using it in my own code.</p> <p>Thanks</p> <pre><code>public static int GetCardinality(BitArray bitArray) { var _bitsSetArray256 = new byte[] {0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8}; var array = (uint[])bitArray.GetType().GetField("m_array", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(bitArray); int count = 0; for (int index = 0; index &lt; array.Length; index ++) count += _bitsSetArray256[array[index] &amp; 0xFF] + _bitsSetArray256[(array[index] &gt;&gt; 8) &amp; 0xFF] + _bitsSetArray256[(array[index] &gt;&gt; 16) &amp; 0xFF] + _bitsSetArray256[(array[index] &gt;&gt; 24) &amp; 0xFF]; return count; } </code></pre>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USJohn_
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POCan someone explain to me what this GetCardinality method is doing?
      1. USMax
      1. VTFavorite
    2. VO
      singulars
      1. POCan someone explain to me what this GetCardinality method is doing?
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POCan someone explain to me what this GetCardinality method is doing?
      1. This table or related slice is empty.
      1. VTUpMod
    1. This table or related slice is empty.
 

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