Fix ps_point reserve capacity

[SteveBronder]

Submission Checklist

• Run unit tests: ./runTests.py src/test/unit
• Run cpplint: make cpplint
• Declare copyright holder and open-source license: see below

Summary

Fixes #3384 and adds names.size() to string reserve

Copyright and Licensing

Please list the copyright holder for the work you are submitting (this will be you or your assignee, such as a university or company): Simons Foundation

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

[stan-buildbot]

---

Name	Old Result	New Result	Ratio	Performance change( 1 - new / old )
gp_regr/gp_regr.stan	0.11	0.1	1.06	5.39% faster
gp_regr/gen_gp_data.stan	0.03	0.24	0.12	-740.27% slower
arK/arK.stan	2.28	2.55	0.89	-11.75% slower
eight_schools/eight_schools.stan	0.07	0.31	0.21	-366.58% slower
low_dim_gauss_mix_collapse/low_dim_gauss_mix_collapse.stan	10.01	9.49	1.06	5.22% faster
pkpd/one_comp_mm_elim_abs.stan	22.66	22.34	1.01	1.4% faster
pkpd/sim_one_comp_mm_elim_abs.stan	0.42	0.35	1.22	17.71% faster
sir/sir.stan	81.54	76.27	1.07	6.46% faster
gp_pois_regr/gp_pois_regr.stan	3.61	3.62	1.0	-0.22% slower
low_dim_gauss_mix/low_dim_gauss_mix.stan	3.21	3.33	0.96	-3.78% slower
irt_2pl/irt_2pl.stan	4.89	4.55	1.08	7.09% faster
arma/arma.stan	0.32	0.3	1.08	7.3% faster
garch/garch.stan	0.98	0.44	2.22	54.86% faster
low_dim_corr_gauss/low_dim_corr_gauss.stan	0.01	0.01	1.01	1.39% faster
performance.compilation	241.94	227.28	1.06	6.06% faster
Mean result: 1.0032743229648309

---

Jenkins Console Log
Blue Ocean
Commit hash: 7a7d72e615616c0f3361edc354f888fe5bb9b0d9

---

Machine information

No LSB modules are available. 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: 46 bits physical, 48 bits virtual
CPU(s): 80
On-line CPU(s) list: 0-79
Thread(s) per core: 2
Core(s) per socket: 20
Socket(s): 2
NUMA node(s): 2
Vendor ID: GenuineIntel
CPU family: 6
Model: 85
Model name: Intel(R) Xeon(R) Gold 6148 CPU @ 2.40GHz
Stepping: 4
CPU MHz: 2400.000
CPU max MHz: 3700.0000
CPU min MHz: 1000.0000
BogoMIPS: 4800.00
Virtualization: VT-x
L1d cache: 1.3 MiB
L1i cache: 1.3 MiB
L2 cache: 40 MiB
L3 cache: 55 MiB
NUMA node0 CPU(s): 0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58,60,62,64,66,68,70,72,74,76,78
NUMA node1 CPU(s): 1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43,45,47,49,51,53,55,57,59,61,63,65,67,69,71,73,75,77,79
Vulnerability Gather data sampling: Mitigation; Microcode
Vulnerability Itlb multihit: KVM: Mitigation: Split huge pages
Vulnerability L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable
Vulnerability Mds: Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Meltdown: Mitigation; PTI
Vulnerability Mmio stale data: Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Reg file data sampling: Not affected
Vulnerability Retbleed: Mitigation; IBRS
Vulnerability Spec rstack overflow: Not affected
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; IBRS; IBPB conditional; STIBP conditional; RSB filling; PBRSB-eIBRS Not affected; BHI Not affected
Vulnerability Srbds: Not affected
Vulnerability Tsx async abort: Mitigation; Clear CPU buffers; SMT vulnerable
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 dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb cat_l3 cdp_l3 invpcid_single pti intel_ppin ssbd mba ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm cqm mpx rdt_a avx512f avx512dq rdseed adx smap clflushopt clwb intel_pt avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local dtherm ida arat pln pts hwp hwp_act_window hwp_epp hwp_pkg_req pku ospke md_clear flush_l1d arch_capabilities

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

[drezap]

I know we can't trust one run of Jenkins for benchmarks. I am also aware that small improvements in C++ language can yield great performance improvements if we're using composing FLOPs and these C++ typing/language improvements can reduce technical debt. Especially, since MCMC uses repeated operations in a for loop, over thousands of iterations. I'm not the main C++ guy, and long term this could be helpful WRT techincal debt, but the huge increase in gp_regre.stan is a huge red flag, since the largest bottleneck in computing GP models is the cholesky decomposition, and the problem with Cholesky decomposition is repeated matrix algebra/FLOPs. So perhaps, somehow, the previous change added some computational complexity? More generally, is there any codified/vetted documentation of benchmarking C++/C implementations and C from a computational perspective, not just theoretical? I'm on hiatus but I am watching. Best, Andre Zapico linkedin.com/in/andre-zapico gitub.com/drezap ME Information and Communication Engineering University of Electronic Science and Technology of China Consultant, Owner likely llc likelyllc.com Stan Developer mc-stan.org BS Mathematical Sciences: Probabilistic Methods BS Statistics University of Michigan, Ann Arbor 2017

…

On Thu, May 14, 2026 at 2:18 PM Brian Ward ***@***.***> wrote: ***@***.**** approved this pull request. — Reply to this email directly, view it on GitHub <#3392 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACY543FYNK3XU2HNGMZDPX342YEWPAVCNFSM6AAAAACY3GSXY2VHI2DSMVQWIX3LMV43YUDVNRWFEZLROVSXG5CSMV3GSZLXHM2DEOJSGM2TQNJZHE> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[stan-buildbot]

---

Name	Old Result	New Result	Ratio	Performance change( 1 - new / old )
gp_regr/gp_regr.stan	0.1	0.1	1.03	2.7% faster
gp_regr/gen_gp_data.stan	0.03	0.02	1.05	4.59% faster
arK/arK.stan	1.86	1.89	0.98	-1.79% slower
eight_schools/eight_schools.stan	0.06	0.06	1.03	3.12% faster
low_dim_gauss_mix_collapse/low_dim_gauss_mix_collapse.stan	9.14	9.19	0.99	-0.6% slower
pkpd/one_comp_mm_elim_abs.stan	21.25	20.33	1.05	4.34% faster
pkpd/sim_one_comp_mm_elim_abs.stan	0.28	0.26	1.06	5.45% faster
sir/sir.stan	77.94	73.84	1.06	5.26% faster
gp_pois_regr/gp_pois_regr.stan	3.16	2.98	1.06	5.94% faster
low_dim_gauss_mix/low_dim_gauss_mix.stan	2.94	2.82	1.04	4.03% faster
irt_2pl/irt_2pl.stan	5.67	4.5	1.26	20.6% faster
arma/arma.stan	0.37	0.31	1.18	15.6% faster
garch/garch.stan	0.54	0.46	1.16	13.99% faster
low_dim_corr_gauss/low_dim_corr_gauss.stan	0.01	0.01	1.1	9.46% faster
performance.compilation	243.49	243.29	1.0	0.08% faster
Mean result: 1.0707039935835618

---

Jenkins Console Log
Blue Ocean
Commit hash: 7a7d72e615616c0f3361edc354f888fe5bb9b0d9

---

Machine information

No LSB modules are available. 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: 46 bits physical, 48 bits virtual
CPU(s): 80
On-line CPU(s) list: 0-79
Thread(s) per core: 2
Core(s) per socket: 20
Socket(s): 2
NUMA node(s): 2
Vendor ID: GenuineIntel
CPU family: 6
Model: 85
Model name: Intel(R) Xeon(R) Gold 6148 CPU @ 2.40GHz
Stepping: 4
CPU MHz: 3399.994
CPU max MHz: 3700.0000
CPU min MHz: 1000.0000
BogoMIPS: 4800.00
Virtualization: VT-x
L1d cache: 1.3 MiB
L1i cache: 1.3 MiB
L2 cache: 40 MiB
L3 cache: 55 MiB
NUMA node0 CPU(s): 0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58,60,62,64,66,68,70,72,74,76,78
NUMA node1 CPU(s): 1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43,45,47,49,51,53,55,57,59,61,63,65,67,69,71,73,75,77,79
Vulnerability Gather data sampling: Mitigation; Microcode
Vulnerability Itlb multihit: KVM: Mitigation: Split huge pages
Vulnerability L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable
Vulnerability Mds: Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Meltdown: Mitigation; PTI
Vulnerability Mmio stale data: Mitigation; Clear CPU buffers; SMT vulnerable
Vulnerability Reg file data sampling: Not affected
Vulnerability Retbleed: Mitigation; IBRS
Vulnerability Spec rstack overflow: Not affected
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; IBRS; IBPB conditional; STIBP conditional; RSB filling; PBRSB-eIBRS Not affected; BHI Not affected
Vulnerability Srbds: Not affected
Vulnerability Tsx async abort: Mitigation; Clear CPU buffers; SMT vulnerable
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 dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid dca sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb cat_l3 cdp_l3 invpcid_single pti intel_ppin ssbd mba ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm cqm mpx rdt_a avx512f avx512dq rdseed adx smap clflushopt clwb intel_pt avx512cd avx512bw avx512vl xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local dtherm ida arat pln pts hwp hwp_act_window hwp_epp hwp_pkg_req pku ospke md_clear flush_l1d arch_capabilities

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

[SteveBronder]

@WardBrian reran this and the jenkins probably just had a hiccup because this was not replicated locally

[drezap]

May be I am wrong Best, Andre Zapico linkedin.com/in/andre-zapico gitub.com/drezap ME Information and Communication Engineering University of Electronic Science and Technology of China Consultant, Owner likely llc likelyllc.com Stan Developer mc-stan.org BS Mathematical Sciences: Probabilistic Methods BS Statistics University of Michigan, Ann Arbor 2017

…

On Fri, May 15, 2026 at 4:59 PM Steve Bronder ***@***.***> wrote: *SteveBronder* left a comment (stan-dev/stan#3392) <#3392 (comment)> @WardBrian <https://github.com/WardBrian> reran this and the jenkins probably just had a hiccup because this was not replicated locally — Reply to this email directly, view it on GitHub <#3392 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACY543EF2JXTXX35DV4SVQT426AMNAVCNFSM6AAAAACY3GSXY2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DINRTGU4DAMZZHA> . You are receiving this because you commented.Message ID: ***@***.***>

[drezap]

But if we set the seed and we’ve only modified one thing shouldn’t the result be the same? So there’s something we’re not controlling for, what am I missing? Best, Andre Zapico linkedin.com/in/andre-zapico gitub.com/drezap ME Information and Communication Engineering University of Electronic Science and Technology of China Consultant, Owner likely llc likelyllc.com Stan Developer mc-stan.org BS Mathematical Sciences: Probabilistic Methods BS Statistics University of Michigan, Ann Arbor 2017

…

On Fri, May 15, 2026 at 6:54 PM Andre Zapico ***@***.***> wrote: May be I am wrong Best, Andre Zapico linkedin.com/in/andre-zapico gitub.com/drezap ME Information and Communication Engineering University of Electronic Science and Technology of China Consultant, Owner likely llc likelyllc.com Stan Developer mc-stan.org BS Mathematical Sciences: Probabilistic Methods BS Statistics University of Michigan, Ann Arbor 2017 On Fri, May 15, 2026 at 4:59 PM Steve Bronder ***@***.***> wrote: > *SteveBronder* left a comment (stan-dev/stan#3392) > <#3392 (comment)> > > @WardBrian <https://github.com/WardBrian> reran this and the jenkins > probably just had a hiccup because this was not replicated locally > > — > Reply to this email directly, view it on GitHub > <#3392 (comment)>, or > unsubscribe > <https://github.com/notifications/unsubscribe-auth/ACY543EF2JXTXX35DV4SVQT426AMNAVCNFSM6AAAAACY3GSXY2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DINRTGU4DAMZZHA> > . > You are receiving this because you commented.Message ID: > ***@***.***> >

[SteveBronder]

The server we run on can just randomly hiccup so it's good to run tests locally if something anomalous happens. The performance benchmarks that Jenkins posts are much more of a canary than a definitive yes/no