Why Does std::random_device Produce Identical Sequences with MinGW 4.8.1?

Reproducibility Issues with std::random_device and MinGW

In C , the library provides access to random numbers. When using with MinGW and the GCC 4.8.1 distribution, users encountered a puzzling issue: identical output sequences across multiple runs.

Analysis

The inconsistent behavior raised questions about the determinism of . To understand the problem, we must refer to the C reference:

"Note that std::random_device may be implemented in terms of a pseudo-random number engine if a non-deterministic source (e.g., a hardware device) is not available to the implementation."

This suggests that when a true random source is unavailable, the library falls back on a pseudo-random generator. However, in the case of MinGW 4.8.1, it appears that even with pseudo-randomness, the output remains consistently predictable.

Suspected Rationale

One theory postulates that this behavior may be intentional. By delivering non-random sequences, the library highlights potential flaws in the randomness of the underlying implementation. This would serve as a warning to developers that the random numbers generated may not be truly unpredictable.

Resolution

To generate genuinely random sequences with MinGW 4.8.1, users can consider using alternative implementations of the random number generators provided in the library. These implementations may incorporate more sophisticated algorithms to improve the unpredictability of output.

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