Make DynamicPPL.TestUtils.run_ad return both the primal and gradient benchmarks

[penelopeysm]

run_ad(...; benchmark=true) used to benchmark logdensity and logdensity_and_gradient, then take the ratio and return that.

This PR makes it return both benchmark results because, I mean, why not? We already have this information.

There is a bit of dangerous scope creep here in that this function is turning into a replacement for TuringBenchmarking. (Note it can't benchmark the primal alone without a gradient though so it's still not the same.)

But I think it's still useful to know both figures separately. For example, in the CI benchmarks table, we tabulate both times.

Unfortunately I attempted to change the CI benchmark setup to use the new functionality #1002 and promptly got bitten by the bug in #1001. So this PR doesn't change that, not for now, at least.

[github-actions]

Benchmark Report for Commit 2c4d913

Computer Information

Julia Version 1.11.6
Commit 9615af0f269 (2025-07-09 12:58 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 4 × AMD EPYC 7763 64-Core Processor
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, znver3)
Threads: 1 default, 0 interactive, 1 GC (on 4 virtual cores)

Benchmark Results

|                 Model | Dimension |  AD Backend |      VarInfo Type | Linked | Eval Time / Ref Time | AD Time / Eval Time |
|-----------------------|-----------|-------------|-------------------|--------|----------------------|---------------------|
| Simple assume observe |         1 | forwarddiff |             typed |  false |                  8.7 |                 1.5 |
|           Smorgasbord |       201 | forwarddiff |             typed |  false |                637.7 |                45.3 |
|           Smorgasbord |       201 | forwarddiff | simple_namedtuple |   true |                409.4 |                55.7 |
|           Smorgasbord |       201 | forwarddiff |           untyped |   true |               1024.6 |                33.9 |
|           Smorgasbord |       201 | forwarddiff |       simple_dict |   true |               6291.5 |                26.7 |
|           Smorgasbord |       201 | reversediff |             typed |   true |               1429.6 |                28.6 |
|           Smorgasbord |       201 |    mooncake |             typed |   true |               1021.0 |                 4.2 |
|    Loop univariate 1k |      1000 |    mooncake |             typed |   true |               5641.1 |                 4.0 |
|       Multivariate 1k |      1000 |    mooncake |             typed |   true |                962.7 |                 9.0 |
|   Loop univariate 10k |     10000 |    mooncake |             typed |   true |              63367.8 |                 3.7 |
|      Multivariate 10k |     10000 |    mooncake |             typed |   true |               8449.5 |                 9.8 |
|               Dynamic |        10 |    mooncake |             typed |   true |                130.8 |                12.0 |
|              Submodel |         1 |    mooncake |             typed |   true |                 13.1 |                 4.6 |
|                   LDA |        12 | reversediff |             typed |   true |               1008.7 |                 3.1 |

[codecov]

Codecov Report

❌ Patch coverage is 28.57143% with 5 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@084f5af). Learn more about missing BASE report.
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/test_utils/ad.jl	28.57%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1009   +/-   ##
=======================================
  Coverage        ?   82.26%           
=======================================
  Files           ?       38           
  Lines           ?     3947           
  Branches        ?        0           
=======================================
  Hits            ?     3247           
  Misses          ?      700           
  Partials        ?        0           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[sunxd3]

@penelopeysm sorry for missing this!

is it a good time to review it?

[penelopeysm]

@sunxd3 Sure, now is as good a time as any other :)

[sunxd3]

there are quite a lot of code changes now, should we do a rebase of this branch to something? sorry for asking

[penelopeysm]

Oh, dear, sorry. I'll sort that.

[github-actions]

DynamicPPL.jl documentation for PR #1009 is available at:
https://TuringLang.github.io/DynamicPPL.jl/previews/PR1009/

[sunxd3]

looks great! ready to go from my side once CI passes

[coveralls]

Pull Request Test Coverage Report for Build 16876123332

Details

• 0 of 7 (0.0%) changed or added relevant lines in 1 file are covered.
• 31 unchanged lines in 8 files lost coverage.
• Overall coverage decreased (-0.04%) to 82.516%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/test_utils/ad.jl	0	7	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/bijector.jl	1	93.33%
src/model.jl	1	86.73%
src/debug_utils.jl	3	89.27%
src/extract_priors.jl	3	60.53%
src/pointwise_logdensities.jl	3	93.06%
src/varinfo.jl	3	85.33%
src/values_as_in_model.jl	4	72.41%
src/threadsafe.jl	13	62.16%

Totals
Change from base Build 16862061135:	-0.04%
Covered Lines:	3247
Relevant Lines:	3935

---

💛 - Coveralls

[penelopeysm]

Thanks @sunxd3!