R version 3.5.0 (2018-04-23) -- "Joy in Playing"
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> Sys.setenv(OMP_THREAD_LIMIT = Sys.getenv("OMP_THREAD_LIMIT", "2"))
> require(data.table)
Loading required package: data.table
> 
> test.data.table()  # runs the main test suite of 5,000+ tests in /inst/tests/tests.Rraw
getDTthreads(verbose=TRUE):
  OpenMP version (_OPENMP)       201307
  omp_get_num_procs()            4
  R_DATATABLE_NUM_PROCS_PERCENT  unset (default 50)
  R_DATATABLE_NUM_THREADS        unset
  R_DATATABLE_THROTTLE           unset (default 1024)
  omp_get_thread_limit()         2147483647
  omp_get_max_threads()          4
  OMP_THREAD_LIMIT               2
  OMP_NUM_THREADS                unset
  RestoreAfterFork               true
  data.table is using 2 threads with throttle==1024. See ?setDTthreads.
test.data.table() running: /builds/Rdatatable/data.table/data.table.Rcheck/data.table/tests/tests.Rraw

**** Full long double accuracy is not available. Tests using this will be skipped.

Test 2365.2 ran without errors but failed check that x equals y:
> x = dcast(df_dcast, a ~ b, value.var = "v") 
   a  1  2  [Key=a Types=int,int,int Classes=fac,int,int]
1: x  3 NA                                               
2: y NA  4                                               
> y = dcast(dt_dcast, a ~ b, value.var = "v") 
   a  1  2  [Key=a Types=cha,int,int Classes=cha,int,int]
1: x  3 NA                                               
2: y NA  4                                               
Datasets have different column modes. First 3: a(numeric!=character)

Fri Jan 30 04:34:37 2026  endian==little, sizeof(long double)==16, capabilities('long.double')==TRUE, longdouble.digits==NULL, sizeof(pointer)==8, TZ=='UTC', Sys.timezone()=='UTC', Sys.getlocale()=='LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=en_US.UTF-8;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C', l10n_info()=='MBCS=TRUE; UTF-8=TRUE; Latin-1=FALSE', getDTthreads()=='OpenMP version (_OPENMP)==201307; omp_get_num_procs()==4; R_DATATABLE_NUM_PROCS_PERCENT==unset (default 50); R_DATATABLE_NUM_THREADS==unset; R_DATATABLE_THROTTLE==unset (default 1024); omp_get_thread_limit()==2147483647; omp_get_max_threads()==4; OMP_THREAD_LIMIT==2; OMP_NUM_THREADS==unset; RestoreAfterFork==true; data.table is using 2 threads with throttle==1024. See ?setDTthreads.', .libPaths()=='/builds/Rdatatable/data.table/data.table.Rcheck','/usr/local/lib/R/library', zlibVersion()==1.2.8 ZLIB_VERSION==1.2.8
Error in test.data.table() : 
  1 error out of 12645. Search tests/tests.Rraw for test number 2365.2. Duration: 39.5s elapsed (42.2s cpu).
Calls: test.data.table -> stopf -> raise_condition -> signal
Execution halted