# CmdStan & Stan 2.33 release candidate
**URL:** https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531
**Category:** General
**Created:** [August 23, 2023, 7:16pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531 "2023-08-23T19:16:31Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@rok\_cesnovar](https://discourse.mc-stan.org/u/rok_cesnovar)
#### Post date: [August 23, 2023, 7:16pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/1 "2023-08-23T19:16:31Z")
I am very happy to announce that the latest release candidates of Cmdstan and Stan are now available on Github!
This release cycle brings a new type - tuples, a new algorithm - Pathfinder, many new functions, and other improvements.
You can find the release candidate for cmdstan [here](https://github.com/stan-dev/cmdstan/releases/tag/v2.33.0-rc1). Instructions for installing are given at the bottom of this post.
Please test the release candidate with your models and report if you experience any problems. We also kindly invite you to test the new features and provide feedback. If you feel some of the new features could be improved or should be changed before the release, please do not hesitate to comment.
The Stan development team appreciates your time and help in making Stan more efficient while maintaining a high level of reliability.
If everything goes according to plan, the 2.33 version will be released in about ten days.
Below are some of the highlights of the new release.
## Tuples
The Stan language gains a new type: tuples!
For any sequence of types, Stan provides a tuple data type. For example,
```stan
tuple(real, array[5] int) xi;
```
declares `xi` to be a tuple holding two values, the first of which is of type type `real` and the second of which a 5-dimensional array of type `int`. Tuples can be of arbitrary size. The values in a tuple can be of arbitrary type, but the component types must be declared along with the declaration of the tuple. Tuples can be manipulated as a whole, or their elements may be accessed and set individually.
Currently, the documentation is available [here](https://github.com/stan-dev/docs/blob/8c818acc94c45cf50a6ab39b90a627d199de2e76/src/reference-manual/types.Rmd#L84) and [here](https://github.com/stan-dev/docs/blob/8c818acc94c45cf50a6ab39b90a627d199de2e76/src/stan-users-guide/matrices-arrays.Rmd#L53).
## Pathfinder
A new Variational Inference algorithm is now available via CmdStan - Pathfinder!
Pathfinder is a variational method for approximately sampling from differentiable log densities. Starting from a random initialization, Pathfinder locates normal approximations to the target density along a quasi-Newton optimization path, with local covariance estimated using the inverse Hessian estimates produced by the L-BFGS optimizer. Pathfinder returns draws from the Gaussian approximation with the lowest estimated Kullback-Leibler (KL) divergence to the true posterior.
For more information see the [preliminary documentation](https://github.com/stan-dev/docs/blob/a9ca6a561d93c23e0f79a698cf9ef3112acc048c/src/cmdstan-guide/pathfinder_intro.Rmd), the [paper](https://arxiv.org/abs/2108.03782) and [Bob Carpenter’s tutorial](https://www.youtube.com/watch?v=TPptuDp-w2E).
## New functions and function signatures
- new functions `qr_thin`, `eigendecompose_sym`, `eigendecompose`, `complex_schur_decompose`, `svd`, and `csr_extract` are now available
- `eigendecompose(A)` is equivalent to `(eigenvectors(A), eigenvalues(A))`
- `eigendecompose_sym(A)` is equivalent to `(eigenvectors_sym(A), eigenvalues_sym(A))`
- `qr_thin(A)` is equivalent to `(qr_thin_Q(A), qr_thin_R(A))`
- `qr(A)` is equivalent to `(qr_Q(A), qr_R(A))`
- `svd(A)` is equivalent to `(svd_U(A), singular_values(A), svd_V(A))`
- `csr_extract(A)` is equivalent to `(csr_extract_w(a), csr_extract_v(a), csr_extract_u(a))`
These functions all return tuples and have a lower computational cost due to the shared work to produce the multiple results.
- added vectorized signatures for `log_sum_exp`
The function now supports all arguments that are typically supported in fully vectorized functions.
## Deprecations
The following deprecations have been turned into errors this version:
- The old array syntax, e.g. `int arr[5];`. Use `array[5] int arr;` instead.
- Distribution functions ending in `_log`. Use either `_lpdf` or `_lpmf`.
- The functions `binomial_coefficient_log`, `multiply_log`, and `cov_exp_quad`. Use `lchoose`, `lmultiply`, and `gp_exp_quad_cov` respectively.
- The `if_else` function. Use the ternary operator `cond ? true_value : false_value`
- Use of CDFs with a `,` between the first and second argument. Use a `|`.
- Comments beginning with `#`. Use `//`.
- Use of `<-` for assignment. Use `=`.
- The `increment_log_prob` function. Use the `target +=` statement.
- The `get_lp()` function. Use `target()`.
- The use of nested multi-indices on the left hand side of an assignment statement.
For this version, these can all be automatically updated with the `--canonicalize=deprecations` argument to the autoformatter. This is not guaranteed to work for versions _following_ this one.
Additionally, the following identifiers are now reserved words: `array`, `offset`, `multiplier`, `lower`, and `upper`.
## Other miscellaneous features
- The `num_chains` argument for running multiple chains with a single executable is now available to all HMC variants other than the `static` engine
- Improved accuracy of `matrix_exp_multiply`
- using the RDump input files now shows a warning - the RDump input files will not support tuples and are unlikely to support othew new types in the future. Please switch to the JSON input.
- Return statements now follow the same type promotion rules as assignment and function argument passing.
## How to install?
Download the tar.gz file from the link above, extract it and use it the way you use any Cmdstan release. We also have an online Cmdstan guide available at CmdStan User’s Guide 1
If you are using cmdstanpy you can install the release candidate using
```python
cmdstanpy.install_cmdstan(version='2.33.0-rc1')
```
With CmdStanR you can install the release candidate using
```r
cmdstanr::install_cmdstan(version = "2.33.0-rc1", cores = 4)
```
---
### Author:  [@jonah](https://discourse.mc-stan.org/u/jonah)
#### Post date: [August 23, 2023, 7:29pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/2 "2023-08-23T19:29:25Z")
> [@rok\_cesnovar](#):
>
> A new Variational Inference algorithm is now available via CmdStan - Pathfinder!
Just want to give users a heads up that pathfinder is not yet available via the interfaces that wrap CmdStan, only in CmdStan. So if you install this release candidate via CmdStanR or CmdStanPy there won’t be a pathfinder method yet. Hopefully we’ll have that ready soon.
---
### Author:  [@spinkney](https://discourse.mc-stan.org/u/spinkney)
#### Post date: [August 23, 2023, 8:18pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/3 "2023-08-23T20:18:33Z")
@rok_cesnovar is that a typo that `qr_thin_R(A)` is equivalent to `(qr_thin_Q(A), qr_thin_R(A)` and should just be `qr_thin(A)`?
---
### Author:  [@rok\_cesnovar](https://discourse.mc-stan.org/u/rok_cesnovar)
#### Post date: [August 23, 2023, 8:59pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/4 "2023-08-23T20:59:28Z")
Fixed, thanks. Was a typo.
---
### Author:  [@mitzimorris](https://discourse.mc-stan.org/u/mitzimorris)
#### Post date: [August 23, 2023, 9:01pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/5 "2023-08-23T21:01:38Z")
here’s the CmdStan documentation on Pathfinder:
Pathfinder overview:
[Pathfinder\_overview.pdf](https://discourse.mc-stan.org/uploads/short-url/mP8H6NDLCDaWQo1qkHaXEORKZYg.pdf) (42.2 KB)
Pathfinder config:
[Pathfinder\_config.pdf](https://discourse.mc-stan.org/uploads/short-url/ixaV520ofDZEz5OQNSEX47NU8lA.pdf) (43.3 KB)
(note: docs have been updated per PR comments)
---
### Author:  [@mike-lawrence](https://discourse.mc-stan.org/u/mike-lawrence)
#### Post date: [August 24, 2023, 12:36pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/6 "2023-08-24T12:36:43Z")
Aki just pointed me to the [cmdstanr branch](https://github.com/stan-dev/cmdstanr/tree/feature/pathfinder) that enables access to pathfinder, but in case it’s useful to anyone, here’s a by-hand way to use it:
```r
run_pathfinder = function(data,mod){
data_file = tempfile(fileext='.json')
output_file = tempfile(fileext='.csv')
cmdstanr::write_stan_json(data,file=data_file)
processx::run(
command = mod$exe_file()
, args = c(
'pathfinder'
, 'data'
, paste0('file=',data_file)
, 'output'
, paste0('file=',output_file)
)
, echo_cmd = T
, stdout = ""
, stderr = "2>&1"
)
(
paste0("grep '^[#l]' '",output_file,"'")
%>% system(intern=T)
%>% strsplit('\n')
%>% unlist()
) -> header
header_nlines = which(stringr::str_starts(header,'lp'))
found_samples_col_names = unlist(strsplit(header[header_nlines],','))
(
data.table::fread(
cmd = paste0(
"tail -n+"
, header_nlines + 1
, " '"
, output_file
, "' | grep -v '^[#]' --color=never"
)
, data.table = FALSE
, sep = ','
, header = F
, col.names = found_samples_col_names
, colClasses = list(numeric=1:length(found_samples_col_names))
)
%>% as_tibble()
) ->
out
return(out)
}
```
---
### Author:  [@mitzimorris](https://discourse.mc-stan.org/u/mitzimorris)
#### Post date: [August 24, 2023, 3:36pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/7 "2023-08-24T15:36:42Z")
I think that particular cmdstanr branch is accessing an old version of CmdStan (never released) which has an earlier implementation of Pathfinder - @jonah ? but I think this code would work when running against the 2.33 RC - although maybe not the output file parsing.
---
### Author:  [@jonah](https://discourse.mc-stan.org/u/jonah)
#### Post date: [August 24, 2023, 3:59pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/8 "2023-08-24T15:59:53Z")
> [@mitzimorris](#):
>
> I think that particular cmdstanr branch is accessing an old version of CmdStan (never released) which has an earlier implementation of Pathfinder - @jonah ?
@stevebronder would know best but my guess is that the CmdStanR branch doesn’t access any particular version of CmdStan but hasn’t been tested with the newer version.
---
### Author:  [@wds15](https://discourse.mc-stan.org/u/wds15)
#### Post date: [August 24, 2023, 9:55pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/9 "2023-08-24T21:55:34Z")
I just tried pathfinder as it sounds soooo powerful. I am getting numbers for my model impressively fast… but right now the lack of support by `cmdstanr` is a problem for me, since the output is so different in term of the format to what my programs are written for that it is difficult to say anything. So getting cmdstanr in shape would be really nice in order to say something.
One more thing: Given that tuples land - which is awesome - is there a possibility to do something like a typedef now? I mean, I would like to define tuples for various things, but I really don’t like to retype the tuple definition over and over again…should I file a feature request to stanc/stan repo (assuming others think that this is good idea)?
I must admit that I have stopped a while ago to update Stan as 2.28 was good enough (and that’s what is on our prod system), but 2.33 is already now on my system - looking forward to see it land!
---
### Author:  [@WardBrian](https://discourse.mc-stan.org/u/WardBrian)
#### Post date: [August 24, 2023, 10:04pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/10 "2023-08-24T22:04:13Z")
> [@wds15](#):
>
> One more thing: Given that tuples land - which is awesome - is there a possibility to do something like a typedef now? I mean, I would like to define tuples for various things, but I really don’t like to retype the tuple definition over and over again…should I file a feature request to stanc/stan repo (assuming others think that this is good idea)?
This is definitely something we want before we’d do structs, which are a natural place to go next.
I’ve also [previously brought up](https://discourse.mc-stan.org/t/the-var-keyword-should-stan-support-local-variable-type-inference/23928) something like C++'s `auto`/Java’s `var` keyword which lets you omit the type on the left hand side of a declare-define. This never made it to the level of design doc, but it would be nice to do still IMO
---
### Author:  [@avehtari](https://discourse.mc-stan.org/u/avehtari)
#### Post date: [August 25, 2023, 7:26am UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/11 "2023-08-25T07:26:51Z")
> [@rok\_cesnovar](#):
>
> The following deprecations have been turned into errors this version:
>
> - The old array syntax, e.g. `int arr[5];`. Use `array[5] int arr;` instead.
@bgoodri any news on getting RStan updated in CRAN? Otherwise, this change will cause a huge amount of problems
---
### Author:  [@mitzimorris](https://discourse.mc-stan.org/u/mitzimorris)
#### Post date: [August 25, 2023, 3:07pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/12 "2023-08-25T15:07:14Z")
> [@wds15](#):
>
> but right now the lack of support by `cmdstanr` is a problem for me, since the output is so different in term of the format to what my programs are written for that it is difficult to say anything. So getting cmdstanr in shape would be really nice in order to say something.
there’s discussion in this issue: [[Stan 2.33] Pathfinder algorithm · Issue #684 · stan-dev/cmdstanpy · GitHub](https://github.com/stan-dev/cmdstanpy/issues/684) - your feedback welcome!
---
### Author:  [@jonah](https://discourse.mc-stan.org/u/jonah)
#### Post date: [August 25, 2023, 4:15pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/13 "2023-08-25T16:15:47Z")
> [@wds15](#):
>
> but right now the lack of support by `cmdstanr` is a problem for me, since the output is so different in term of the format to what my programs are written for that it is difficult to say anything. So getting cmdstanr in shape would be really nice in order to say something.
Until the discussion in the issue @mitzimorris linked is finished and someone has time to implement it I think @mike-lawrence’s code above should work and give you usable results in a data frame.
---
### Author:  [@jonah](https://discourse.mc-stan.org/u/jonah)
#### Post date: [August 25, 2023, 4:27pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/15 "2023-08-25T16:27:06Z")
> [@avehtari](#):
>
> > [@rok\_cesnovar](#):
> >
> > The following deprecations have been turned into errors this version:
> >
> > - The old array syntax, e.g. `int arr[5];`. Use `array[5] int arr;` instead.
>
> @bgoodri any news on getting RStan updated in CRAN? Otherwise, this change will cause a huge amount of problems
I opened a GitHub issue about this. Has there been coordination with the people working on RStan recently (@bgoodri, @andrjohns, @hsbadr) to avoid this? Last I heard a version of RStan with the new array syntax is ready to go, so we should be ok, but I don’t know if there’s a specific plan for submitting it.
---
### Author:  [@WardBrian](https://discourse.mc-stan.org/u/WardBrian)
#### Post date: [August 25, 2023, 4:47pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/16 "2023-08-25T16:47:11Z")
> [@jonah](#):
>
> Has there been coordination with the people working on RStan recently
These removals were originally scheduled for 2.32 but delayed at the request of @andrjohns because RStan 2.26 was imminent (at the time). Since then there hasn’t been much discussion
---
### Author:  [@WardBrian](https://discourse.mc-stan.org/u/WardBrian)
#### Post date: [August 28, 2023, 8:11pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/17 "2023-08-28T20:11:30Z")
People interested in trying Pathfinder through a preliminary version of cmdstanpy can use the branch from [this PR](https://github.com/stan-dev/cmdstanpy/pull/686):
`pip install -e git+https://github.com/stan-dev/cmdstanpy@feature/pathfinder#egg=cmdstanpy`
Note: when this is eventually released, it will probably be CmdStanPy 2.0 due to some breaking changes in the interfaces for optimization and ADVI (short version: the `stan_variable` methods had some inconsistencies which have been ironed out, but required changing some return types/behavior for those classes). So, if you heavily used those methods previously you may need to make changes
---
### Author:  [@StaffanBetner](https://discourse.mc-stan.org/u/StaffanBetner)
#### Post date: [August 29, 2023, 2:13pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/18 "2023-08-29T14:13:06Z")
I can’t really get this to work in Windows due to some library not being statically linked. Will try to find a solution. (I guess WSL work as an alternative)
I get this error when I run the compiled model executable:
> The program can’t start because libwinpthread-1.dll is missing. Try reinstalling the program to fix the problem.
which gives this result in R:
```no-highlight
> run_pathfinder(examplemodel1_standata, examplemodel1_cmdstan_model) ->
+ pathfinder_test
Running "C:/Users/xxx/AppData/Local/Temp/RtmpCoHwpg/model_a19ad56e9a836376e1ccd44d6a405c6d.exe" pathfinder data \
"file=C:\Users\xxx\AppData\Local\Temp\RtmpCoHwpg\file7c043b8a7ba8.json" output "file=C:\Users\xxx\AppData\Local\Temp\RtmpCoHwpg\file7c047f441aba.csv"
Opening fd 1
Error:
! ! System command 'model_a19ad56e9a836376e1ccd44d6a405c6d.exe' failed
```
---
### Author:  [@ssp3nc3r](https://discourse.mc-stan.org/u/ssp3nc3r)
#### Post date: [August 29, 2023, 3:01pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/19 "2023-08-29T15:01:39Z")
I just tried the above cmdstanr branch that enables access to pathfinder with 2.33 rc and it seemed to work. Also, unless I missed something, it looked like the GitHub commits on that branch were mergeable with the latest cmdstanr. Though I think there’s some question as to what to call some of the interface options.
---
### Author:  [@martinmodrak](https://discourse.mc-stan.org/u/martinmodrak)
#### Post date: [August 29, 2023, 4:29pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/20 "2023-08-29T16:29:07Z")
Lots of cool stuff, looking forward to using it. I assume this discussion happened somewhere, so please point me there if relevant, but with all the backwards-incompatible changes, shouldn’t we be bumping the major verison? Could avoid some of the confusion…
---
### Author:  [@WardBrian](https://discourse.mc-stan.org/u/WardBrian)
#### Post date: [August 29, 2023, 4:40pm UTC](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531/21 "2023-08-29T16:40:30Z")
> [@martinmodrak](#):
>
> I assume this discussion happened somewhere
Yes, two years ago it began in [this thread](https://discourse.mc-stan.org/t/a-deprecation-schedule-for-stan/24228) before moving to a [design document](https://github.com/stan-dev/design-docs/pull/43). The summary of the policy is these changes are allowed because a user can automatically update their model
[Next page](https://discourse.mc-stan.org/t/cmdstan-stan-2-33-release-candidate/32531.md?page=2)