(netCDF 3.4) Patch for more versatile "assigns" on Cray Computers

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: (netCDF 3.4) Patch for more versatile "assigns" on Cray Computers
• From: Olaf Heudecker <oheudeck@xxxxxxxxxxxxxxxxxx>
• Date: Tue, 17 Mar 1998 14:19:21 +0100 (MET)

Patch for more versatile "assigns" on Cray Computers

Problem:
-------
The implementation with "ffopens" allows only to pass a simple "assign"
parameter (namely the option following -F to determine the buffer
structure). For those who like to fiddle around with ALL assign
options (to determine the partitions and reserved block sizes and so
on) for optimization, I added some additional lines to libsrc/ffio.c.

Implementation:
------------
Here is a patch to netCDF version 3.4 for users of Cray Supercomputers
(tested for T3E only but it should run on all Unicos machines supplying the
fast flexible I/O (ffio) scheme, especially the Fortran ASSIGN
command).Instead of using the ffopens-command the Fortran ASSIGN
command is called to pass the options. To provide full compatabilty an
extra environment  variable called NETCDF_XFFIOSPEC ist introduced and
appended to the parameters of the assign command. Schematically:
assign -F $NETCDF_FFIOSPEC $NETCDF_XFFIOSPEC

Extra functionality:
--------------
Now there is an extra environment variable called "NETCDF_XFFIOSPEC"
which holds additional options to the assign command. For
compatibility reasons the -F option is still passed via
"NETCDF_FFIOSPEC". This seems a bit complicated but it assures
that even the not patched programms (including ncdump and ncgen) will
work without errors.

Example (bourne shell grammer):
------------------------
Type 
NETCDF_FFIOSPEC="cachea:8:350"
NETCDF_XFFIOSPEC="-p 0:1 -d 100"
and run a (patched) netCDF-programm. Then when reading or writing a
file it will use 350 asynchronous Buffers of 8 * 512kwords size each
AND place it only on partitions 0 and 1 of the (respectively designed)
file system, changing partitions every 100 Blocks (512kwords each).

Note: 
The cited NETCDF_FFIOSPEC yielded a factor 1/10 in execution time for
a programm that randomly accessed a netCDF file (array rearrangements).

To apply the patch:
---------------
1) write the block between --------start and --------end into a file
    (preferably patch_ffio)
1) walk down to netcdf-3.4/src/libsrc
2) faint hearted people make a copy of the original (recommended)
3) type: "patch patch ffio.c ffio.c path_of_ffio/patch_ffio" (symbolically)
4) recompile netCDF, ncgen and ncdump
Patch (context patch) follows:
--------start
*** ffio.c.orig Thu Mar 12 10:08:00 1998
--- ffio.c      Thu Mar 12 17:23:05 1998
***************
*** 16,21 ****
--- 16,23 ----
  #include <ffio.h>
  #include <unistd.h>
  #include <string.h>
+ /* Insertion by O. R. Heudecker, AWI-Bremerhaven 12.3.98 (1 line)*/
+ #include <fortran.h>
  
  #include "ncio.h"
  #include "fbits.h"
***************
*** 477,487 ****
        {
                 ControlString="bufa:336:2";
        }
! 
        if(fIsSet(ioflags, NC_NOCLOBBER))
                fSet(oflags, O_EXCL);
  
!       fd = ffopens(path, oflags, 0666, 0, &stat, ControlString);
        if(fd < 0)
        {
                status = errno;
--- 479,513 ----
        {
                 ControlString="bufa:336:2";
        }
!       /* Insertion by Olaf Heudecker, AWI-Bremerhaven, 12.8.1998
!          to allow more versatile FFIO-assigns */
!       /* begin new */
!       { 
!         char assignstr[128];
!         char emptystr=' ';
!         char *xtra_assign;
!         xtra_assign = getenv("NETCDF_XFFIOSPEC");
!         if(xtra_assign == NULL)
!           {
!             xtra_assign=&emptystr;
!           }
!         if (strlen(ControlString)+strlen(xtra_assign)+21 > 127) {
!           /* Error: AssignCommand too long */
!           status=E2BIG;
!           goto unwind_new;
!         }
!         sprintf(assignstr,"assign -F %s %s f:%s",ControlString,
!                 xtra_assign,path);
!         /* printf("1 assignstr=>%s<\n",assignstr); */
!         /* Aufruf der Fortran-Routine assign von C aus */
!         ASSIGN(_cptofcd(assignstr,strlen(assignstr)));
!       }
!       /* end new */
        if(fIsSet(ioflags, NC_NOCLOBBER))
                fSet(oflags, O_EXCL);
  
!       /* Orig: fd = ffopens(path, oflags, 0666, 0, &stat, ControlString); */
!       fd = ffopen(path, oflags, 0666, 0, &stat);
        if(fd < 0)
        {
                status = errno;
***************
*** 559,566 ****
        {
                 ControlString="bufa:336:2";
        }
  
!       fd = ffopens(path, oflags, 0, 0, &stat, ControlString);
        if(fd < 0)
        {
                status = errno;
--- 585,618 ----
        {
                 ControlString="bufa:336:2";
        }
+       /* Insertion by Olaf Heudecker, AWI-Bremerhaven, 12.8.1998
+          to allow more versatile FFIO-assigns */
+       /* begin new */
+       { 
+         char assignstr[128];
+         char emptystr=' ';
+         char *xtra_assign;
+         xtra_assign = getenv("NETCDF_XFFIOSPEC");
+         if(xtra_assign == NULL)
+           {
+             xtra_assign=&emptystr;
+           }
+         if (strlen(ControlString)+strlen(xtra_assign)+21 > 127) {
+           /* Error: AssignCommand too long */
+           status=E2BIG;
+           goto unwind_new;
+         }
+         sprintf(assignstr,"assign -F %s %s f:%s",ControlString,
+                 xtra_assign,path);
+         /* printf("2 assignstr=>%s<\n",assignstr); */
+         /* Aufruf der Fortran-Routine assign von C aus */
+         ASSIGN(_cptofcd(assignstr,strlen(assignstr)));
+       }
+       /* end new */
  
!       /* Orig: fd = ffopens(path, oflags, 0, 0, &stat, ControlString); */
!       fd = ffopen(path, oflags, 0, 0, &stat);
! 
        if(fd < 0)
        {
                status = errno;
--------end

Have fun
Olaf R. Heudecker