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feat(libxce-alloc-preason-equality): public alloc_eq/host_alloc_eq/job_alloc_eq with first-difference description (task 2.1)

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Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Rongsong Shen 2026-09-28 09:35:08 +00:00
parent 8f25c1c3f3
commit a6cbb323b0
Signed by untrusted user: rshen
GPG key ID: 80533536B0EB651C
6 changed files with 952 additions and 5 deletions
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51
src/include/xcealloc.h
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@ -16,4 +16,55 @@ extern xce_job_account_t* make_job_account(xce_job_alloc_t*);
extern xce_job_alloc_t* dup_job_alloc(const xce_job_alloc_t*);
extern int merge_job_alloc(xce_job_alloc_t*, const xce_job_alloc_t*);
/*
* Allocation equality: "do these two records describe the same allocation
* decision".
*
* alloc_eq() compares, in this order: resname, reserve, value, duration,
* from. `value` is compared exactly (`==`, no floating-point tolerance): both
* sides are exact copies of the same double, so any difference is real.
* `from` (the reservation start time) is compared: the scheduler stamps it
* with the deciding session's start, which a replay reproduces. `instid` is
* NOT compared: it comes from a per-process counter (sched_get_id()) whose
* value depends on how many allocations that process built before, so a
* recording and its replay give the same allocation different instids
* (bug-1844).
*
* This is not merge_job_alloc()'s slot matching. merge_job_alloc() asks
* "are these the same reservation slot to add into" (resname, instid,
* reserve; value ignored because merging adds values), where instid IS
* significant. Neither predicate can stand in for the other.
*
* host_alloc_eq() compares host, then nallocs, then allocs[i] in order.
* job_alloc_eq() compares jobid, nhosts, nres_shared, then allocs[i] in
* order, then allocs_shared[i] in order. Lists are order-sensitive: the same
* entries in a different order are not equal.
*
* NULL handling: identical pointers (including two NULLs) are equal; exactly
* one NULL argument, list entry or string field is not equal. Precondition:
* a non-zero count with a NULL entry array is a malformed record and is not
* handled. Neither argument is modified.
*
* `why` is optional. When NULL, nothing is allocated. Otherwise *why is set
* to NULL when the arguments are equal, or to a newly allocated,
* NUL-terminated description of the first difference found, in comparison
* order, e.g.
* allocs[1](host=h1).allocs[0](resname=mem).value: 2 != 3
* allocs[0](host=h0).host: "h0" != "h2"
* allocs_shared[0]: NULL != non-NULL
* nhosts: 1 != 2
* job_alloc: non-NULL != NULL (a NULL top-level argument)
* Path labels come from `a`, from `b` when a's entry/string is NULL, or are
* `?`. The caller owns the description and releases it with free(). The value
* *why holds on entry is never read or freed. If allocating the description
* fails, *why is NULL and the result is unchanged. Nothing is logged.
*
* Returns non-zero when equal, 0 when not.
*/
extern int alloc_eq(const xce_alloc_t* a, const xce_alloc_t* b, char** why);
extern int host_alloc_eq(const xce_host_alloc_t* a, const xce_host_alloc_t* b,
char** why);
extern int job_alloc_eq(const xce_job_alloc_t* a, const xce_job_alloc_t* b,
char** why);
#endif