[GRASS5] MAXFILES in libgis too low

[Markus Neteler]

On Fri, Mar 25, 2005 at 03:10:39PM +1200, Hamish wrote:
> > while trying to export a few hundred maps into a
> > big ERDAS/IMG multichannel file (using the GDAL/GRASS plugin
> > and gdal_merge.py), I stumbled over
> > 
> >  lib/gis/G.h :#define MAXFILES    256
> > 
> > While this number is lower than 365 days, Radim
> > reminded me of the memory allocation.
> > 
> > How to deal with this problem? Simply changing
> > MAXFILES to a higher number will cause problems
> > on handhelds.
> 
> Low memory or stripped down kernel maxfiles?
> 

No, it's sort of unrelated to kernel maxfiles.
The point is that in lib/gis/G.h the fileinfo struct
is allocated as fileinfo[MAXFILES]. So all the contents
of this struct are allocated as often as MAXFILES is
defined.

> 
> FWIW, boosting G.h to 400 (ie >365) for use with r.series works fine
> for me.

I tried 1024, no problem. But: in this case we have "lost"
struct fileinfo[1024] memory allocation.

In this struct fileinfo are
- 10 ints				: 4 * 10 = 40
- 1 double				: 8 * 8  = 64
- 4 chars				: 1 * 4  =  4
- 3 unsigned chars			: 1 * 3  =  3
- 6 further structs:
   - Cell_head (include/gis.h): 	
          - 9 ints			: 4 * 9  = 36
          - 11 doubles			: 8 * 11 = 88
   - Reclass:
          - 2 chars			: 1 * 2  =  2
          - 2 ints			: 4 * 2  =  8
          - 3 CELL			: 4 * 3  = 12
   - Cell_stats
          - struct Cell_stats_node
                - 3 ints 		: 4 * 3  = 12
                - 1 long		: 4 * 1  =  4 (or 8 * 1 = 8)
          - 4 ints			: 4 * 4  = 16 
          - 1 long			: 4 * 1  =  4
   - Range
          - 1 int			: 4 * 1  =  4
          - 2 CELL			: 4 * 2  =  8
   - FPRange
          - 1 int			: 4 * 1  =  4
          - 2 DCELL			: 8 * 2  = 16
   - Quant
           - 9 ints			: 4 * 9  = 36
           - 6 CELLs			: 4 * 6  = 24
           - 6 DCELLs			: 8 * 6  = 48
           - struct Quant_table		
                   - 2 CELLs		: 4 * 2  =  8
                   - 2 DCELLs		: 8 * 2  = 16
           - struct fp_lookup
                   - 2 ints		: 4 * 2  =  8
                   - 2 CELLs		: 4 * 2  =  8
                   - 2 DCELLs		: 8 * 2  = 16
                   - struct Quant_table
                      - 2 CELLs		: 4 * 2  =  8
                      - 2 DCELLs	: 8 * 2  = 16
- 1 off_t				: 4 * 1  =  4
- 1 RASTER_MAP_TYPE: typedef int	: 4 * 1  =  4
- 1 COLUMN_MAPPING: typedef int		: 4 * 1  =  4
- 1 XDR: register/typedef struct	: ?  (/usr/include/rpc/xdr.h)

======================================================
 SUM                                              525 bytes + XDR

So we would allocate 525 bytes * 1024 = 537600 (+ XDR!)
When running GRASS, around 0.5MB of RAM are immediately consumed.

It's likely that I made some mistakes but I just wanted
to estimate it.

Using
 fprintf(stderr,"sizeof fileinfo: %d\n", sizeof(struct fileinfo));
prints 600 bytes. This number then multiplied by MAXFILES...

So it becomes quite memory consuming for handhelds.

Markus