cling

[Ben Goodrich]

I recently discovered cling

http://root.cern.ch/drupal/content/cling
http://root.cern.ch/drupal/content/what-cling

cling is an interactive C++ interpreter, which they claim can handle anything that clang handles. I think cling could be used sort-of like a debugger for the C++ code that stanc generates.

Ben

[Ben Goodrich]

https://www.youtube.com/watch?v=g7-tskP0OzI

/opt/cling/bin$ ./stan.sh # just loads math.hpp with correct includes
****************** CLING ******************
* Type C++ code and press enter to run it *
*             Type .q to exit             *
*******************************************
[cling]$ double y = 1.3;
[cling]$ stan::math::var mu = 0.5, sigma = 1.2;
[cling]$ stan::math::var lp = 0;
[cling]$ lp -= 0.5 * log(2 * stan::math::pi());
[cling]$ lp -= log(sigma);
[cling]$ lp -= 0.5 * pow((y - mu) / sigma, 2);
[cling]$ std::cout << "f(mu, sigma) = " << lp.val() << std::endl;
f(mu, sigma) = -1.32348
[cling]$ lp.val() // simpler alternative since cling is an interpreter
(double) -1.32348
[cling]$ lp.grad();
[cling]$ std::cout << " d.f / d.mu = " << mu.adj() << std::endl << " d.f / d.sigma = " << sigma.adj() << std::endl;
 d.f / d.mu = 0.555556
 d.f / d.sigma = -0.462963
[cling]$ .q

But you need a login to play with it.

Ben

[Allen Riddell]

If this sort of thing is possible perhaps we can bundle this (or
something similar) into the executable and just interpret (transpiled)
Stan program code? It would certainly be great to skip that compilation
step.

Or will this just never work with code involving templates?

On 08/28/2016 08:55 PM, Ben Goodrich wrote:
> On Monday, October 15, 2012 at 6:19:27 PM UTC-4, Ben Goodrich wrote:
>
> I recently discovered cling
>
> http://root.cern.ch/drupal/content/cling

> <http://root.cern.ch/drupal/content/cling>
> http://root.cern.ch/drupal/content/what-cling

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[Ben Goodrich]

On Monday, August 29, 2016 at 5:00:13 PM UTC-4, riddell6 wrote:

If this sort of thing is possible perhaps we can bundle this (or
something similar) into the executable and just interpret (transpiled)
Stan program code? It would certainly be great to skip that compilation
step.

Or will this just never work with code involving templates?

It can parse whatever clang can parse because it uses clang to parse it. The Stan Math Library certainly has a lot of templating that it handles fine:

****************** CLING ******************
* Type C++ code and press enter to run it *
*             Type .q to exit             *
*******************************************

[cling]$ stan::math::log_sum_exp(2, 3)
(boost::math::tools::promote_args<int, int, float, float, float, float>::type) 3.31326
[cling]$ stan::math::var two(2);
[cling]$ stan::math::log_sum_exp(two, 3)
(boost::math::tools::promote_args<int, stan::math::var, float, float, float, float>::type) @0x696b840
[cling]$ stan::math::log_sum_exp(two, 3).val()
(double) 3.31326
[cling]$ .q

But bundling it seems like a tall order since it uses a modified LLVM / clang and LLVM / clang is huge.

Ben