[SteveBronder]

Summary

Grouped tests share the process-wide TBB initializer, so a construction test cannot assume it is the first caller. Extract independently owned concurrency-control and arena state for construction tests, preserve the initializer's first-call-wins behavior, and restore STAN_NUM_THREADS after tests that change it.

Part 3 of the CMake migration split from #3463.

Targets cmake-split/02-opencl-context (#3502) as the preceding layer of the native stack. The review contains only this layer's prepared patch and its supporting tests.

Tests

• Reproduced the original grouped initialization failure.
• Ten shuffled grouped-core repetitions pass with threading enabled and ten with it disabled.
• All four affected Make test executables pass independently.

Side Effects

Adds an internal construction helper. The public initializer retains its original concurrency configuration after the first call.

Release notes

Make TBB construction tests independent of process-wide initialization.

Checklist

• Copyright holder: Simons Foundation
• The complete basic-test and CI matrix is passing
• C++ idioms and Doxygen documentation have completed review
• Focused validation is passing as described above; remaining coverage is listed

Related PRs

• 1/7: [CMake 1/7] Fix test compilation with strict compiler warnings
• 2/7: [CMake 2/7] Share OpenCL kernel-cache registration across translation units
• 3/7: [CMake 3/7] Isolate TBB construction tests from process-wide initialization (this PR)
• 4/7: [CMake 4/7] Make probability test fixtures safe for grouped linking
• 5/7: [CMake 5/7] Make unit tests safe for grouped execution
• 6/7: [CMake 6/7] Initialize CVODES adjoint quadrature derivative buffers
• 7/7: [CMake 7/7] Add CMake builds and migrate the test runner and CI

Native stack: https://github.com/stan-dev/math/stack/3509

[stan-buildbot]

Name	Old Result	New Result	Ratio	Performance change( 1 - new / old )
stat_comp_benchmarks/benchmarks/gp_regr/gp_regr.stan	0.24	0.25	1.0	-0.43% slower
stat_comp_benchmarks/benchmarks/gp_regr/gen_gp_data.stan	0.06	0.06	0.99	-0.58% slower
stat_comp_benchmarks/benchmarks/low_dim_corr_gauss/low_dim_corr_gauss.stan	0.02	0.02	0.97	-2.66% slower
stat_comp_benchmarks/benchmarks/arma/arma.stan	0.69	0.69	1.0	0.14% faster
stat_comp_benchmarks/benchmarks/arK/arK.stan	3.43	3.4	1.01	0.96% faster
stat_comp_benchmarks/benchmarks/pkpd/one_comp_mm_elim_abs.stan	42.8	42.65	1.0	0.34% faster
stat_comp_benchmarks/benchmarks/pkpd/sim_one_comp_mm_elim_abs.stan	0.59	0.58	1.0	0.19% faster
stat_comp_benchmarks/benchmarks/gp_pois_regr/gp_pois_regr.stan	4.66	4.81	0.97	-3.2% slower
stat_comp_benchmarks/benchmarks/low_dim_gauss_mix_collapse/low_dim_gauss_mix_collapse.stan	21.88	21.94	1.0	-0.27% slower
stat_comp_benchmarks/benchmarks/garch/garch.stan	1.01	1.01	1.0	-0.24% slower
stat_comp_benchmarks/benchmarks/eight_schools/eight_schools.stan	0.11	0.12	0.97	-2.61% slower
stat_comp_benchmarks/benchmarks/irt_2pl/irt_2pl.stan	9.42	9.29	1.01	1.35% faster
stat_comp_benchmarks/benchmarks/low_dim_gauss_mix/low_dim_gauss_mix.stan	6.67	6.58	1.01	1.34% faster
stat_comp_benchmarks/benchmarks/sir/sir.stan	228.09	227.36	1.0	0.32% faster
performance.compilation	374.7	371.36	1.01	0.89% faster
Mean result: 0.9972245899725701

Jenkins Console Log
Jenkins Build Stages
Commit hash: 148669cf074a47c2622971790ef9133551135df7

Machine information

Distributor ID:	Ubuntu
Description:	Ubuntu 20.04.3 LTS
Release:	20.04
Codename:	focal

CPU:

Architecture:                            x86_64
CPU op-mode(s):                          32-bit, 64-bit
Byte Order:                              Little Endian
Address sizes:                           43 bits physical, 48 bits virtual
CPU(s):                                  256
On-line CPU(s) list:                     0-255
Thread(s) per core:                      2
Core(s) per socket:                      64
Socket(s):                               2
NUMA node(s):                            2
Vendor ID:                               AuthenticAMD
CPU family:                              23
Model:                                   49
Model name:                              AMD EPYC 7742 64-Core Processor
Stepping:                                0
Frequency boost:                         enabled
CPU MHz:                                 1497.281
CPU max MHz:                             3416.0681
CPU min MHz:                             1500.0000
BogoMIPS:                                4491.79
Virtualization:                          AMD-V
L1d cache:                               4 MiB
L1i cache:                               4 MiB
L2 cache:                                64 MiB
L3 cache:                                512 MiB
NUMA node0 CPU(s):                       0-63,128-191
NUMA node1 CPU(s):                       64-127,192-255
Vulnerability Gather data sampling:      Not affected
Vulnerability Indirect target selection: Not affected
Vulnerability Itlb multihit:             Not affected
Vulnerability L1tf:                      Not affected
Vulnerability Mds:                       Not affected
Vulnerability Meltdown:                  Not affected
Vulnerability Mmio stale data:           Not affected
Vulnerability Old microcode:             Not affected
Vulnerability Reg file data sampling:    Not affected
Vulnerability Retbleed:                  Mitigation; untrained return thunk; SMT enabled with STIBP protection
Vulnerability Spec rstack overflow:      Mitigation; Safe RET
Vulnerability Spec store bypass:         Mitigation; Speculative Store Bypass disabled via prctl
Vulnerability Spectre v1:                Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:                Mitigation; Retpolines; IBPB conditional; STIBP always-on; RSB filling; PBRSB-eIBRS Not affected; BHI Not affected
Vulnerability Srbds:                     Not affected
Vulnerability Tsa:                       Not affected
Vulnerability Tsx async abort:           Not affected
Vulnerability Vmscape:                   Mitigation; IBPB before exit to userspace
Flags:                                   fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology nonstop_tsc cpuid extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 x2apic movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3 cdp_l3 hw_pstate ssbd mba ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 cqm rdt_a rdseed adx smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local clzero irperf xsaveerptr rdpru wbnoinvd amd_ppin arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif v_spec_ctrl umip rdpid overflow_recov succor smca sev sev_es

G++:

g++ (Ubuntu 9.4.0-1ubuntu1~20.04) 9.4.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Clang:

clang version 10.0.0-4ubuntu1 
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin