What Is Best Fit in Data Structure?


Heather Bennett

In the world of data structures, there are various algorithms and strategies that can be used to optimize the storage and retrieval of data. One such strategy is known as the Best Fit algorithm. In this article, we will explore what Best Fit is and how it works.

What is Best Fit?

Best Fit is a memory allocation algorithm that aims to find the smallest available free block of memory that can accommodate a given data size. It is commonly used in operating systems and memory management systems to efficiently allocate memory space to processes or programs.

How does Best Fit work?

When a new request for memory allocation comes in, the Best Fit algorithm searches for the smallest free block of memory that can hold the requested size. It compares the size of each available free block with the requested size and selects the one with minimum wastage (i.e., the difference between the block size and requested size).

Let’s understand this with an example:

  • Step 1: Assume we have a total memory space of 100 units, divided into several blocks.
  • Step 2: Initially, all blocks are marked as free.
  • Step 3: A request comes in for allocating 30 units of memory.

The Best Fit algorithm will start searching for a suitable block by comparing sizes:

  1. Block 1: Size = 50 units (Free)
  2. – Wastage = Block Size – Requested Size = 50 – 30 = 20 units

  3. Block 2: Size = 20 units (Free)
  4. – Wastage = Block Size – Requested Size = 20 – 30 = -10 units (Negative wastage is not considered)

  5. Block 3: Size = 40 units (Free)
  6. – Wastage = Block Size – Requested Size = 40 – 30 = 10 units

  7. Block 4: Size = 60 units (Free)
  8. – Wastage = Block Size – Requested Size = 60 – 30 = 30 units

The Best Fit algorithm will select Block 3 as it has the minimum wastage of only 10 units. The requested memory will be allocated in this block.

Advantages of Best Fit algorithm:

The Best Fit algorithm offers several advantages:

  • Efficient space utilization: By selecting the smallest available block that can accommodate the requested size, the Best Fit algorithm ensures efficient utilization of memory space.
  • Moderate fragmentation: Compared to other allocation strategies, such as First Fit or Next Fit, Best Fit results in moderate fragmentation. This means that free blocks are more likely to remain larger and available for future allocations.
  • Balanced allocation: The Best Fit algorithm aims to distribute allocations evenly across memory blocks, preventing excessive wastage or block size imbalances.

Disadvantages of Best Fit algorithm:

Despite its advantages, the Best Fit algorithm has some drawbacks:

  • Higher time complexity: Searching for the smallest free block among all available blocks requires traversing the entire list of blocks. This results in a higher time complexity compared to other allocation algorithms.
  • Potential fragmentation issues: Although Best Fit aims to minimize wastage, it can still result in external fragmentation over time. This occurs when small blocks of free memory are scattered throughout the memory space, making it challenging to allocate larger contiguous blocks.

In conclusion, the Best Fit algorithm is an efficient strategy for memory allocation that prioritizes finding the smallest available block that can accommodate a given data size. It offers efficient space utilization, moderate fragmentation, and balanced allocation.

However, it also has some disadvantages like higher time complexity and potential fragmentation issues. Understanding these trade-offs can help in selecting the most suitable memory allocation strategy for a specific use case.

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