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Hi,
qsort callbackhit_sorter_by_evalue may return random result when input structs have all compared fields equal. This in turn may causes inconsistent order or evencrashes in some qsort implementations.
The issue has been detected when running standard testsuite underSortChecker:
cmsearch[23540]: qsort: comparison function is not symmetric (comparison function 0x4ab689 (/home/yugr/build/infernal-1.1.1/src/cmsearch+0x4ab689), called from 0x4abb66 (/home/yugr/build/infernal-1.1.1/src/cmsearch+0x4abb66), cmdline is "../src/cmsearch -E 0.1 --tblout esltmpaa22822.OUTFILES.tbl esltmpaa22822.OUTFILES.cm esltmpaa22822.OUTFILES.fa")Closer examination in debugger reveals thathit_sorter_by_evalue returns returns the same value for equal results:
(gdb) p hit_sorter_by_evalue(&h->hit[2], &h->hit[3])$15 = -1(gdb) p hit_sorter_by_evalue(&h->hit[3], &h->hit[2])$16 = -1The fix is simply to replace final comparison
return (h1->pass_idx < h2->pass_idx ? 1 : -1 ); /* fourth key, pass_idx, high to low */with
return (h1->pass_idx < h2->pass_idx ? 1 : h1->pass_idx > h2->pass_idx ? -1 : 0); /* fourth key, pass_idx, high to low */A similar issue seems to exist in most otherhit_sorter* callbacks .
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