[Users] CarpetIOScalar: avoiding "reductions" for scalar variables

Kelly, Bernard J. (GSFC-660.0)[UNIVERSITY OF MARYLAND BALTIMORE COUNTY] bernard.j.kelly at nasa.gov
Wed Jan 5 15:52:24 CST 2011

Thanks, Erik.

I looked at CarpetIOASCII 0D before, but thought it couldn't be the right
thing, as it outputs many columns of meaningless information (I.e.,
columns 3 through 12 of the general IOASCII output, including levels,
coordinate indices, and coordinate values). The IOScalar output has the
advantage of being smaller & easier to read. Apart from the reduction
issue, it's not clear to me that it's a worse choice than IOASCII/0D.

Follow-on question, which applies to both thorns: I actually have three
scalar variables -- the components of a 3-vector. Ideally, I'd like to
output them in a single file. This works OK, as they're in a group, and
I've activated the "one_file_per_group" option.

But ... I actually have one of these scalar groups per apparent horizon.
Here's the declaration in my interface.ccl:

REAL test_scalars[num_horizons] TYPE=scalar
} "Testing horizon scalar"

When I request scalar output of test_x[0], I get a file with test_x[0] in
its name.

When I request scalar output of the group test_scalars[0], I get a file
with test_scalars in its name -- no "[0]".

Do you know why the horizon index is dropped for group output? If I
request scalar output of the group test_scalars[0] -and- of
test_scalars[1], what will happen? This seems like a bug to me.


On 1/5/11 3:56 PM, "Erik Schnetter" <schnetter at cct.lsu.edu> wrote:

>CarpetIOScalar is for outputting reduction results; this does not
>really apply to scalar variables. You can output scalar variables
>without reduction using CarpetIOASCII; this is called "0D" output
>there since scalars are 0-dimensional grid variables (this is also how
>they are implemented internally).
>out0D_vars = "..."
>out0D_every = ...
>You can also use 0D output to output multi-dimensional grid variables
>at a certain point, e.g. the origin.
>On Wed, Jan 5, 2011 at 7:28 PM, Kelly, Bernard J.
><bernard.j.kelly at nasa.gov> wrote:
>> Hi all. This seems trivial, but ...
>> How do I avoid reductions (average, minimum, maximum, etc) for scalar
>> of a SCALAR variable in CarpetIOScalar?
>> CactusBase/IOBasic recognises the SCALAR type of the variable, and
>> bother with reduction.
>> Carpet/CarpetIOScalar seems to ignore the type, and does the
>>reductions. At
>> least, it outputs several files with trivial information in them. I can
>> force it to only generate one file by setting outscalar_reductions
>> ="average" (for instance), but then I lose the reductions for all other
>> (non-SCALAR) variables.
>> Thanks,
>> Bernard [working with the Chandrasekhar release of ETK]
>> _______________________________________________
>> Users mailing list
>> Users at einsteintoolkit.org
>> http://lists.einsteintoolkit.org/mailman/listinfo/users
>Erik Schnetter <schnetter at cct.lsu.edu>   http://www.cct.lsu.edu/~eschnett/

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