matlab-diagnose-parfor

Run MATLAB's code analyser (checkcode or codeIssues) on the file to get the exact error, then identify the conflicting access pattern. Common causes include struct fields used as sliced outputs, indexed reductions, or mixing sliced writes with whole-variable reads, each of which has a specific restructuring fix.

Change the loop keyword to parfor, then run the code analyser to verify every variable fits exactly one classification: loop, sliced, broadcast, reduction, or temporary. Fix any reported violations, such as conditional assignments or inconsistent subscript patterns, before running.

Sliced variables require first-level parenthesis or brace indexing with the loop variable; dot-indexing on a struct field is never valid for slicing. Extract each field into its own array, slice those arrays in the loop, then pack the struct after the loop.

No, it targets classification errors that prevent parfor from running, not performance tuning. Slow-but-working parfor loops, pool configuration, and worker setup are explicitly out of scope.

A reduction variable must appear as the whole variable in the form X = X op expr, where op is an associative operator like + or .* or a function like max or union. Indexed reductions like counts(bin) = counts(bin) + 1 are not supported and must be restructured as whole-variable reductions.

Temporary variables are discarded when a parfor loop ends by design. If a value conditionally computed inside the loop is needed afterward, store per-iteration results as sliced output and reduce them after the loop, for example with max.