Can GUIDs Really Guarantee Uniqueness? A Practical Demonstration

GUID is not absolutely unique: simple disproof

The common belief that GUID is unique has been questioned. This article provides a simple C# program to demonstrate the non-uniqueness of GUID, and comes with an improved version to improve the stability and performance of the program.

Initial procedure

The initial program attempts to iterate through a series of GUIDs, a process expected to take a long time. However, due to its simple implementation, it failed to produce the expected results.

Improved version

In order to solve this problem, the program has been refactored:

• Use HashSet to store a large number of GUIDs (bigHeapOGuids).
• Create multiple threads to continuously generate new GUIDs and check for conflicts with bigHeapOGuids.

Program execution

The program first fills bigHeapOGuids with as many GUIDs as possible, effectively exhausting available memory. The thread then starts generating GUIDs and searches bigHeapOGuids for a match. This process continues indefinitely, assuming the universe has not yet ended.

Potential Problems

The program relies on OutOfMemoryException to indicate when the memory for generating the GUID has been exhausted. This is considered inefficient and can lead to unpredictable behavior.

Memory Management

To improve memory management, the program has been updated to use the garbage collector more efficiently. The GC automatically manages memory allocation and deallocation, allowing programs to run indefinitely.

Follow up

Despite these improvements, the program still assumes that the universe has not yet ended. If the heat death of the universe occurs, the program will shut down gracefully.

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