fix: use seed48() for complete RNG state initialization

[nh13]

Summary

• Replaces srand48() with seed48() to initialize all 48 bits of the RNG state
• Uses standard 0x330e value for upper 16 bits as per POSIX specification
• Ensures consistent initialization across platforms

Fixes #106

Test plan

• Unit tests pass (make test-unit)
• Integration tests pass (make test-integration)
• Verified reproducibility with explicit seed values

🤖 Generated with Claude Code

Summary by CodeRabbit

• Improvements
  • Improved random seed initialization to use a full 48-bit state for more robust, consistent, and reproducible random number generation.

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📥 Commits

Reviewing files that changed from the base of the PR and between 72961e7 and df1c3d9.

📒 Files selected for processing (1)

• src/dwgsim_opt.c

📝 Walkthrough

Walkthrough

Replaces srand48() with seed48() in src/dwgsim_opt.c, building a 3-word xseed array (from provided seed or time, with upper word 0x330e) and calling seed48() to initialize the full 48-bit RNG state.

Changes

Cohort / File(s)	Summary
RNG State Initialization src/dwgsim_opt.c	Replaced srand48() with seed48() usage: constructs unsigned short xseed[3] from chosen seed (time-based when seed == -1 or provided), sets xseed[2] = 0x330e, and calls seed48(xseed) to fully initialize 48-bit RNG state.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 I nudged a seed into the loam at night,
Three little words now set the bits just right.
Forty-eight whispers spun from time and hand,
A hop, a hum — reproducible land. 🌿✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: replacing srand48() with seed48() for complete RNG state initialization, which directly aligns with the primary objective of the changeset.
Linked Issues check	✅ Passed	The code changes in src/dwgsim_opt.c implement the proposed fix from issue #106 exactly: constructing an unsigned short xseed[3] array with seed high/low 16-bit words and 0x330e for the upper word, then calling seed48(xseed). Tests pass as required.
Out of Scope Changes check	✅ Passed	All changes are directly related to issue #106's objective of replacing srand48() with seed48() for full 48-bit RNG state initialization; no out-of-scope modifications are present.

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📜 Review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 26e3aa9 and 34e4ecb.

⛔ Files ignored due to path filters (5)

• testdata/ex1.test.bfast.fastq.gz is excluded by !**/*.gz
• testdata/ex1.test.bwa.read1.fastq.gz is excluded by !**/*.gz
• testdata/ex1.test.bwa.read2.fastq.gz is excluded by !**/*.gz
• testdata/ex1.test.mutations.txt.gz is excluded by !**/*.gz
• testdata/ex1.test.mutations.vcf.gz is excluded by !**/*.gz

📒 Files selected for processing (1)

• src/dwgsim_opt.c