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Rename zip() to zip_index() - #3416

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SteveBronder merged 2 commits into
stan-dev:developfrom
stekien:feature/rename-zip-to-zip-index
Oct 1, 2026
Merged

SteveBronder merged 2 commits into
stan-dev:developfrom
stekien:feature/rename-zip-to-zip-index

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@stekien

@stekien stekien commented Sep 24, 2026 •

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Summary

Renames stan::math::zip to stan::math::zip_index — the old name implied the
usual zip semantics of pairing two sequences, whereas the function gathers
matrix elements at paired row/column indices. Covers the header, test file,
include guard, error-check name strings, and test names. zip merged after
5.4.0 and has never shipped, so no deprecation alias is needed.

Also renames the reverse-mode overload in stan/math/rev/fun/zip_index.hpp and its include in rev/fun.hpp.

While renaming, the signature was generalized: index arguments go from concrete
std::vector<int> to templated IdxRows/IdxCols under require_all_vector_t
with forwarding references, the body is wrapped in make_holder to keep
forwarded temporaries alive, and the check_range sweeps are guarded by
STAN_NO_RANGE_CHECKS. No change in results.

Related to stan-dev/stanc3#1704

Tests

Existing tests renamed to MathFunctions.zip_index and
MathFunctions.zip_index_errors in
test/unit/math/prim/fun/zip_index_test.cpp;
Reverse-mode tests renamed to AgradRev.zip_index_*
in test/unit/math/rev/fun/zip_index_test.cpp.;
contents unchanged apart from the
rename. Both pass.

Side Effects

None. zip is unreleased, so no user code can depend on the old name.

Release notes

Renamed zip() to zip_index().

Checklist

  • Copyright holder: Simons Foundation

  • the basic tests are passing

    • unit tests pass (./runTests.py test/unit/math/prim/fun/zip_index_test.cpp)
    • header checks pass (make stan/math/prim/fun/zip_index.hpp-test)
    • dependencies checks pass (make test-math-dependencies)
    • docs build (make doxygen)
    • code passes cpplint
  • the code is written in idiomatic C++ and changes are documented in the doxygen

  • the new changes are tested

@SteveBronder

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Thanks! I also added a stan/math/rev/fun/zip.hpp and associated test. Could you update those names as well?

Renames stan::math::zip to stan::math::zip_index, along with the
header, the unit test file, the include guard, the function-name
strings in the error checks, and the test names. No behavioral
change.

The original name suggested the usual zip semantics of combining two
sequences into pairs, whereas the function gathers matrix elements at
paired row/column indices.

Related to stan-dev/stanc3#1704
@stekien
stekien force-pushed the feature/rename-zip-to-zip-index branch from 9556064 to b13902b Compare September 24, 2026 20:23
@stan-buildbot

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Name Old Result New Result Ratio Performance change( 1 - new / old )
stat_comp_benchmarks/benchmarks/gp_regr/gp_regr.stan 0.23 0.23 0.99 -1.03% slower
stat_comp_benchmarks/benchmarks/gp_regr/gen_gp_data.stan 0.06 0.06 1.0 -0.22% slower
stat_comp_benchmarks/benchmarks/low_dim_gauss_mix/low_dim_gauss_mix.stan 6.33 6.32 1.0 0.14% faster
stat_comp_benchmarks/benchmarks/low_dim_corr_gauss/low_dim_corr_gauss.stan 0.02 0.02 0.98 -1.82% slower
stat_comp_benchmarks/benchmarks/irt_2pl/irt_2pl.stan 8.45 8.44 1.0 0.21% faster
stat_comp_benchmarks/benchmarks/gp_pois_regr/gp_pois_regr.stan 4.47 4.49 0.99 -0.53% slower
stat_comp_benchmarks/benchmarks/sir/sir.stan 165.95 166.08 1.0 -0.08% slower
stat_comp_benchmarks/benchmarks/garch/garch.stan 0.89 0.89 1.0 0.47% faster
stat_comp_benchmarks/benchmarks/arma/arma.stan 0.72 0.71 1.01 1.24% faster
stat_comp_benchmarks/benchmarks/pkpd/one_comp_mm_elim_abs.stan 42.69 42.73 1.0 -0.11% slower
stat_comp_benchmarks/benchmarks/pkpd/sim_one_comp_mm_elim_abs.stan 0.6 0.6 1.01 0.67% faster
stat_comp_benchmarks/benchmarks/low_dim_gauss_mix_collapse/low_dim_gauss_mix_collapse.stan 20.87 20.8 1.0 0.31% faster
stat_comp_benchmarks/benchmarks/eight_schools/eight_schools.stan 0.11 0.11 1.0 0.36% faster
stat_comp_benchmarks/benchmarks/arK/arK.stan 3.19 3.19 1.0 -0.09% slower
performance.compilation 385.55 390.3 0.99 -1.23% slower
Mean result: 0.9989175658961245

Jenkins Console Log
Jenkins Build Stages
Commit hash: 41a5a9b9e7d9963091a42eb85eef0571afbb0cab

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:                                 1496.904
CPU max MHz:                             3416.0681
CPU min MHz:                             1500.0000
BogoMIPS:                                4491.85
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

@SteveBronder

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Odd, jenkins keeps failing somewhere totally unrelated to this PR. This is happening across a bunch of different PRs so I'll look into it.

@stan-buildbot

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Name Old Result New Result Ratio Performance change( 1 - new / old )
stat_comp_benchmarks/benchmarks/gp_regr/gp_regr.stan 0.23 0.23 1.01 0.58% faster
stat_comp_benchmarks/benchmarks/gp_regr/gen_gp_data.stan 0.06 0.06 1.01 0.88% faster
stat_comp_benchmarks/benchmarks/low_dim_gauss_mix/low_dim_gauss_mix.stan 6.33 6.32 1.0 0.14% faster
stat_comp_benchmarks/benchmarks/low_dim_corr_gauss/low_dim_corr_gauss.stan 0.02 0.02 0.97 -3.31% slower
stat_comp_benchmarks/benchmarks/irt_2pl/irt_2pl.stan 8.48 8.44 1.01 0.51% faster
stat_comp_benchmarks/benchmarks/gp_pois_regr/gp_pois_regr.stan 4.52 4.49 1.01 0.58% faster
stat_comp_benchmarks/benchmarks/sir/sir.stan 165.66 165.53 1.0 0.08% faster
stat_comp_benchmarks/benchmarks/garch/garch.stan 0.89 0.89 1.0 0.09% faster
stat_comp_benchmarks/benchmarks/arma/arma.stan 0.71 0.71 1.0 0.14% faster
stat_comp_benchmarks/benchmarks/pkpd/one_comp_mm_elim_abs.stan 42.73 42.64 1.0 0.21% faster
stat_comp_benchmarks/benchmarks/pkpd/sim_one_comp_mm_elim_abs.stan 0.6 0.61 0.99 -0.57% slower
stat_comp_benchmarks/benchmarks/low_dim_gauss_mix_collapse/low_dim_gauss_mix_collapse.stan 20.87 20.76 1.01 0.54% faster
stat_comp_benchmarks/benchmarks/eight_schools/eight_schools.stan 0.11 0.11 1.01 1.17% faster
stat_comp_benchmarks/benchmarks/arK/arK.stan 3.19 3.18 1.0 0.3% faster
performance.compilation 385.78 383.82 1.01 0.51% faster
Mean result: 1.0013343352542543

Jenkins Console Log
Jenkins Build Stages
Commit hash: 41a5a9b9e7d9963091a42eb85eef0571afbb0cab

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:                                 1497.233
CPU max MHz:                             3416.0681
CPU min MHz:                             1500.0000
BogoMIPS:                                4491.85
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

@stan-buildbot

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Contributor
Name Old Result New Result Ratio Performance change( 1 - new / old )
stat_comp_benchmarks/benchmarks/gp_regr/gp_regr.stan 0.23 0.23 1.01 1.46% faster
stat_comp_benchmarks/benchmarks/gp_regr/gen_gp_data.stan 0.06 0.06 1.01 0.92% faster
stat_comp_benchmarks/benchmarks/low_dim_corr_gauss/low_dim_corr_gauss.stan 0.02 0.02 1.02 1.97% faster
stat_comp_benchmarks/benchmarks/arma/arma.stan 0.71 0.71 1.01 0.77% faster
stat_comp_benchmarks/benchmarks/arK/arK.stan 3.22 3.21 1.0 0.49% faster
stat_comp_benchmarks/benchmarks/pkpd/one_comp_mm_elim_abs.stan 42.94 42.84 1.0 0.22% faster
stat_comp_benchmarks/benchmarks/pkpd/sim_one_comp_mm_elim_abs.stan 0.6 0.6 1.0 -0.19% slower
stat_comp_benchmarks/benchmarks/gp_pois_regr/gp_pois_regr.stan 4.51 4.47 1.01 0.85% faster
stat_comp_benchmarks/benchmarks/low_dim_gauss_mix_collapse/low_dim_gauss_mix_collapse.stan 20.83 20.87 1.0 -0.19% slower
stat_comp_benchmarks/benchmarks/garch/garch.stan 0.89 0.88 1.0 0.49% faster
stat_comp_benchmarks/benchmarks/eight_schools/eight_schools.stan 0.11 0.11 1.0 0.01% faster
stat_comp_benchmarks/benchmarks/irt_2pl/irt_2pl.stan 8.47 8.44 1.0 0.36% faster
stat_comp_benchmarks/benchmarks/low_dim_gauss_mix/low_dim_gauss_mix.stan 6.31 6.33 1.0 -0.32% slower
stat_comp_benchmarks/benchmarks/sir/sir.stan 165.55 165.97 1.0 -0.26% slower
performance.compilation 385.96 375.16 1.03 2.8% faster
Mean result: 1.0063663709819388

Jenkins Console Log
Jenkins Build Stages
Commit hash: 327f8cfc9b195a36c06f83b385bd1d0d4b2a52e9

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:                                 1496.413
CPU max MHz:                             3416.0681
CPU min MHz:                             1500.0000
BogoMIPS:                                4491.56
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

@SteveBronder
SteveBronder merged commit 9a7998a into stan-dev:develop Oct 1, 2026
34 checks passed
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