Fix mv read loop hardcoding 4 instead of nnode

[sbryngelson]

Summary

Severity: HIGH — mv data file loop uses wrong bounds and offsets when nnode != 4.

File: src/pre_process/m_start_up.fpp, lines 479-482

The pb (pressure) read loop just above correctly uses nnode for both the loop bound and file number offset calculation. The mv (mass/velocity) read loop immediately below hardcodes 4 instead.

Before

! pb loop (correct)
do r = 1, nnode
    write (file_num, '(I0)') sys_size + r + (i - 1)*nnode
    file_loc = ... '/pb' ...

! mv loop (wrong)
do r = 1, 4                                              ! should be nnode
    write (file_num, '(I0)') sys_size + r + (i - 1)*4    ! should be nnode
    file_loc = ... '/mv' ...

After

do r = 1, nnode
    write (file_num, '(I0)') sys_size + r + (i - 1)*nnode

Why this went undetected

nnode is 4 in the most common configuration, so the hardcoded value happens to be correct.

Test plan

• Run bubble restart with non-default nnode value
• Verify all mv data files are read correctly

🤖 Generated with Claude Code

Fixes #1210

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Nitpicks 🔍

🔒 No security issues identified

⚡ Recommended areas for review Parallel I/O inconsistency The serial mv loop was updated to use nnode, but the parallel ic-reading loop still uses a hardcoded 4 in the bound sys_size + 2*nb*4. This is an inconsistency: parallel I/O ranges should be updated to use nnode as well (or otherwise validated) so serialized and parallel read logic match. File-number string width file_num is allocated with length based only on sys_size digits. When computing filenames with indices like sys_size + r + (i-1)*nnode (and the pb/mv ranges), the printed numeric value may require more digits than computed. This can lead to truncated filenames or incorrect file names when nnode, nb, or sys_size grows. Ensure file_num can hold the maximum index used. Serial mv loop update The serial mv file-read loop was changed to iterate r=1..nnode and to compute the file number using nnode (sys_size + r + (i-1)*nnode). Verify this matches the intended file-numbering scheme for all nb and nnode combinations and is consistent with the pb loop. Validate with non-default nnode to ensure expected files are opened and read.

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Pull request overview

This PR fixes a bug in the bubble restart file reading logic where the mv data file loop was hardcoded to iterate 4 times instead of using the nnode variable, which could cause incorrect file reads when nnode != 4.

Changes:

• Updated the mv data file loop to use nnode instead of the hardcoded value 4
• Corrected the file number offset calculation to use nnode for proper indexing

[codecov]

Codecov Report

❌ Patch coverage is 10.00000% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 44.05%. Comparing base (84c46e0) to head (5838245).

Files with missing lines	Patch %	Lines
src/common/m_mpi_common.fpp	7.14%	13 Missing ⚠️
src/pre_process/m_start_up.fpp	0.00%	3 Missing ⚠️
src/pre_process/m_global_parameters.fpp	33.33%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1190   +/-   ##
=======================================
  Coverage   44.05%   44.05%           
=======================================
  Files          70       70           
  Lines       20498    20498           
  Branches     1990     1990           
=======================================
  Hits         9030     9030           
  Misses      10329    10329           
  Partials     1139     1139           

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