[Users] SphericalHarmonicRecon and SphericalHarmonicReconGen

[Yosef Zlochower]

On 07/13/2017 11:33 AM, Frank Loeffler wrote:
> On Thu, Jul 13, 2017 at 11:29:12AM -0400, Yosef Zlochower wrote:
>> On 07/13/2017 11:25 AM, Frank Loeffler wrote:
>>> On Thu, Jul 13, 2017 at 11:14:00AM -0400, Yosef Zlochower wrote:
>>>>  if (minval(abs(zeta - dcmplx(1,1))) < 1.0d-10) then
>>>>         Tarr = minloc(abs(stereo_q(:,1)-1.))
>>>>         loc_q = Tarr(1)
>>>>         Tarr = minloc(abs(stereo_p(1,:)-1.))
>>>>         loc_p = Tarr(1)
>>>>         if (abs(zeta(loc_q,loc_p) - dcmplx(1.,1.)) .gt. 1d-10) then
>>>>            call CCTK_WARN(0, " Error ")
>>>>         endif
>>>>
>>>>      endif
>>>> or one complex one (zeta). With zeta = q + i * p. The code is checking
>>>> that if zeta == 1+i anywhere, that it is equal to 1 + i at the point
>>>> where q=1 and p=1.
>>>
>>> I don't quite understand something about that code. It looks for a
>>> location where q is closest to 1, and one where p is closest to i:
>>>
>>>   minloc(abs(stereo_q(:,1)-1.))
>>>   minloc(abs(stereo_p(1,:)-1.))
>>>
>>> It then assumes the respective 'other' coordinate is the one it should
>>> be looking at:
>>>
>>>   zeta(loc_q,loc_p)
>>>
>>> Is this really always the case (could be, if this comes from some kind
>>> of known grid setup, but this is not apparent from the code).
>>>
>>
>>
>> I don't understand the test either, but it should be the case that
>> dble(zeta) = stereo_q
>> and dimag(zeta) = stereo_p
>>
>> zeta is initialized as  zeta      = dcmplx(stereo_q,stereo_p)
>> in pittnullcode/NullGrid/src/NullGrid_InitCoord.F90
> 
> If that is all, loc_q would be a location in zeta(:,1) where the real 
> part is close to 1, and loc_p is a location in zeta(1,:) where the 
> imaginary part is close to 1. In general, that wouldn't necessarily mean 
> that at location zeta(loc_q,loc_p) any of the parts would be close to 1, 
> let along both at the same time.

stereo_q should be constant along the second coordinate and stereo_p 
along the first.
> 
> Frank
>