Use of non-standard intrinsic function ISNAN

[smueller]

Context

The compilation of source:/NEMO/releases/r4.0/r4.0.6/src/OCE/stpctl.F90#L173​ fails on some architectures.

Analysis

The intrinsic function ISNAN is non-standard and does not seem to be supported by all commonly used Fortran compilers. Instead, recent Fortran standards require the availability of the function ieee_is_nan from the intrinsic module ieee_arithmetic.

Recommendation

An optional wrapper function with the name ISNAN that calls the ieee_is_nan function is proposed to be included in source:/NEMO/releases/r4.0/r4.0-HEAD/src/OCE/lib_fortran.F90​,

src/OCE/lib_fortran.F90

@@ -21 +21 @@
    USE in_out_manager  ! I/O manager
    USE lib_mpp         ! distributed memory computing
    USE lbclnk          ! ocean lateral boundary conditions
+   USE, INTRINSIC :: ieee_arithmetic
 
    IMPLICIT NONE
    PRIVATE
@@ -34 +35 @@
 #if defined key_nosignedzero
    PUBLIC SIGN
 #endif
+#if defined key_noisnan
+   PUBLIC ISNAN
+#endif
 
    INTERFACE glob_sum
       MODULE PROCEDURE glob_sum_1d, glob_sum_2d, glob_sum_3d
@@ -485 +489 @@
    END FUNCTION SIGN_ARRAY_3D_B
 #endif
 
+#if defined key_noisnan
+!$AGRIF_DO_NOT_TREAT
+   FUNCTION ISNAN(pa)
+       USE, INTRINSIC ::   ieee_arithmetic
+       REAL(wp), INTENT(in) ::   pa
+       LOGICAL ::   ISNAN
+       ISNAN = ieee_is_nan(pa)
+   END FUNCTION ISNAN
+!$AGRIF_END_DO_NOT_TREAT
+#endif
+
    !!======================================================================
 END MODULE lib_fortran

and to be made available (if defined) in module stpctl through

src/OCE/stpctl.F90

@@ -25 +25 @@
    USE lib_mpp         ! distributed memory computing
    USE zdf_oce ,  ONLY : ln_zad_Aimp       ! ocean vertical physics variables
    USE wet_dry,   ONLY : ll_wd, ssh_ref    ! reference depth for negative bathy
-
+   USE lib_fortran
    USE netcdf          ! NetCDF library
    IMPLICIT NONE
    PRIVATE

This wrapper function can be activated by defining the pre-processor key key_noisnan in architecture files that configure the compilation using Fortran compilers without support for the ISNAN intrinsic function; it is protected from AGRIF pre-processing to avoid problems from using intrinsic module ieee_arithmetic in AGRIF-processed source code.

[smueller]

In 15371:

Error: Failed to load processor CommitTicketReference

No macro or processor named 'CommitTicketReference' found

[smueller]

source:/NEMO/releases/r4.0/r4.0-HEAD@15371​ has passed the standard SETTE tests.