[ET Trac] [Einstein Toolkit] #1610: Switch Cactus to 64 bits

[Einstein Toolkit]

#1610: Switch Cactus to 64 bits
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  Reporter:  eschnett     |       Owner:                     
      Type:  enhancement  |      Status:  new                
  Priority:  major        |   Milestone:                     
 Component:  Cactus       |     Version:  development version
Resolution:               |    Keywords:                     
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Comment (by eschnett):

 If you need an integer grid functions with a particular range, then you
 would be using CCTK_INT4 or CCTK_INT8. CCTK_INT is a "natural integer
 type", same as CCTK_REAL is a "natural floating-point type". If you run on
 a machine where ints have 64 bits, then CCTK_INT has 64 bits.

 Using ptrdiff_t doesn't interoperate well with Fortran. We can introduce a
 new type for this -- CCTK_PTRDIFF_T or some equivalent name --and make
 this type available e.g. for aliased functions etc.

 CCTK_INT is currently most used in aliased functions as well as in source
 code as an integer type e.g. for index variables and similar, and less for
 grid functions where a particular number of bits is expected. Thus
 introducing CCTK_PTRDIFF_T would require channging a lot of code, whereas
 the places where people use CCTK_INT in grid functions in a way that would
 break when CCTK_INT has 64 bits is very rare.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1610#comment:3>
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