[Users] Piraha in the Flesh

Steven R. Brandt sbrandt at cct.lsu.edu
Wed Feb 20 17:57:03 CST 2013

On 02/06/2013 06:37 PM, Steven R. Brandt wrote:
I haven't heard a lot of feedback about this feature yet, but I thought 
I'd mention a recent improvement.

Piraha allows array notation in parameter files so that instead of 
writing this:

     CarpetRegrid2::radius_1[1]  =  10
     CarpetRegrid2::radius_1[2]  =   5

you can write this:
     CarpetRegrid2::radius_1 = [10,5]

The nice thing about having a parser is that the various features 
combine, so you can also write this:
     CarpetRegrid2::radius_1 = [
         2+2*4 # This should be 10

> I've hacked a version of Cactus to use Piraha for parameter parsing. 
> Please take a look:
> https://svn.cactuscode.org/flesh/branches/with_piraha
> This version is able to run the ET testsuite.
> This version can understand the variables $parfile, $ENV{name}, and 
> $pi (which is 3.14...). Variables can be standalone, or be substituted 
> from inside strings.
> It can understand mathematical expressions including grouping, order 
> of operation, and a few functions (sin, cos, tan, exp, sqrt). Other 
> parameters from the parameter file are available for use in 
> mathematical expressions.
> Some debug printing is in place so you can get an idea of what's going 
> on.
> Cheers,
> Steve

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