Add optional support for CarpetEvolutionMask to GRHydro

Comments (5)

Roland Haas reporter

changed status to open
removed comment

2012-08-02T15:02:09+00:00

Erik Schnetter

removed comment

Most Fortran compilers (and Cactus expects this, and Simfactory sets the respective compiler options) support "Cray pointers". These are pointer-sized integers that can be used in very much the same way as pointers in C.

The syntax is slightly unintuitive if one comes from C; instead of an operator that allows dereferencing a pointer, there is a second variable declared for this operation, similar in spirit to Fortran's "equivalence" statement.

The syntax goes approximately like this:

CCTK_REAL var(ni,nj,nk) pointer (pvar, var) pvar = ... call flesh function to set pointer var(i,j,k) = ... The "pointer" statement declares a pointer, and the pointer type is taken from the second variable. In C, this would be something like

typeof(var) *pvar; In addition, the "pointer" statement means that the variable "var" has no memory allocated; instead, accessing var implicitly dereferences the pointer "pvar". In C, "var" becomes "*pvar".

Technically, pvar is declared as an integer variable with sufficient size to hold a pointer, probably an integer*8 on most systems. As such, pvar can e.g. also be output, passed to subroutines, etc. However, this is rarely necessary -- for almost all purposes, "var" can be used like a regular variable; the only difference is that its memory isn't allocated by the compiler, but by setting "pvar".

There is also an intrinsic function "loc" to obtain the address of a variable, similar to C's "&" operator.

2012-08-02T15:25:57+00:00

Roland Haas reporter

changed status to open
removed comment

2012-11-29T17:36:43+00:00

Roland Haas reporter

changed status to resolved
removed comment

Functionality contained in ~~#1078~~ which is already up for review.

2012-11-29T17:40:32+00:00

Roland Haas reporter

edited description
changed status to closed

2019-02-21T19:53:36+00:00

Roland Haas reporter
- changed status to open
- removed comment
- 2012-08-02T15:02:09+00:00
Erik Schnetter
- removed comment
Most Fortran compilers (and Cactus expects this, and Simfactory sets the respective compiler options) support "Cray pointers". These are pointer-sized integers that can be used in very much the same way as pointers in C.

The syntax is slightly unintuitive if one comes from C; instead of an operator that allows dereferencing a pointer, there is a second variable declared for this operation, similar in spirit to Fortran's "equivalence" statement.

The syntax goes approximately like this:

CCTK_REAL var(ni,nj,nk) pointer (pvar, var) pvar = ... call flesh function to set pointer var(i,j,k) = ... The "pointer" statement declares a pointer, and the pointer type is taken from the second variable. In C, this would be something like

typeof(var) *pvar; In addition, the "pointer" statement means that the variable "var" has no memory allocated; instead, accessing var implicitly dereferences the pointer "pvar". In C, "var" becomes "*pvar".

Technically, pvar is declared as an integer variable with sufficient size to hold a pointer, probably an integer*8 on most systems. As such, pvar can e.g. also be output, passed to subroutines, etc. However, this is rarely necessary -- for almost all purposes, "var" can be used like a regular variable; the only difference is that its memory isn't allocated by the compiler, but by setting "pvar".

There is also an intrinsic function "loc" to obtain the address of a variable, similar to C's "&" operator.
- 2012-08-02T15:25:57+00:00
Roland Haas reporter
- changed status to open
- removed comment
- 2012-11-29T17:36:43+00:00
Roland Haas reporter
- changed status to resolved
- removed comment
Functionality contained in ~~#1078~~ which is already up for review.
- 2012-11-29T17:40:32+00:00
Roland Haas reporter
- edited description
- changed status to closed
- 2019-02-21T19:53:36+00:00
Log in to comment