Load factor and rehashing in hashsets

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In summary, the conversation discusses the concept of load factor in HashTables and the potential advantages and disadvantages of setting it below or at 100%. It also mentions the need for rehashing when increasing capacity and whether there is a way to avoid it. The Wiki article provided mentions the increase in overhead when the load factor exceeds 2/3rds, but does not mention the time it takes to initialize a hash table to empty. The issue of optimizing dynamic capacity is also brought up.
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ndesk1900
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I had some general questions related to hashing.

1. Load factor in a HashTable is when you want to increase capacity of buffer. Is there any advantage/disadvantage of setting the loadfactor less than 100% vs setting load factor at 100%?

2. When you increase capacity, you have to rehash all values inside. Is there any way to increase capacity without a rehash?

This is crossposted on [http://stackoverflow.com/questions/13120021/load-factor-and-rehashing-in-hashsets]
 
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  • #2
Wiki article mentions overhead increases once the load factor exceeds about 2/3rds.

http://en.wikipedia.org/wiki/Hash_table#Load_factor

Not mentioned is the time it takes to iniitialize a hash table to empty, which could be an issue with a huge hash table in an attempt to produce a very low load factor (or one with a huge capacity). I don't know how to optimize dynamic capacity.
 

Related to Load factor and rehashing in hashsets

1. What is load factor in a hashset?

Load factor in a hashset refers to the measure of how full the hashset is. It is calculated by dividing the number of elements in the hashset by the total number of buckets in the hashset. A higher load factor means that the hashset is more densely populated.

2. How does load factor affect the performance of a hashset?

The load factor of a hashset directly affects its performance. As the load factor increases, the chances of collision (when two or more elements have the same hashcode) also increases. This can lead to a decrease in performance, as the hashset will need to perform additional operations to resolve the collisions.

3. What is rehashing in a hashset?

Rehashing in a hashset is the process of resizing the hashset when the load factor exceeds a certain threshold. This is necessary to maintain a low load factor and avoid too many collisions. During rehashing, the hashset creates a new, larger array and rehashes all the elements from the original array into the new one.

4. How does rehashing improve the performance of a hashset?

Rehashing helps to improve the performance of a hashset by reducing the load factor and minimizing the chances of collisions. With a lower load factor, the hashset can retrieve elements faster and with fewer collisions, resulting in better overall performance.

5. What is the ideal load factor for a hashset?

The ideal load factor for a hashset depends on the specific implementation and use case. In general, a load factor of around 0.75 is considered to be a good balance between minimizing collisions and avoiding excessive memory usage. However, this may vary depending on the size and complexity of the data being stored in the hashset.

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