[GRASS5] [bug #823] (grass) rast problems dealing with null maps on DEC Alpha (Linux)

[Glynn Clements]

Request Tracker wrote:

> this bug's URL: http://intevation.de/rt/webrt?serial_num=823
> -------------------------------------------------------------------------
> 
> Subject: rast problems dealing with null maps on DEC Alpha (Linux)
> 
> Platform: Linux/Alpha64
> Linux distro: Debian
> linux cpu: Alpha
> Xwindows version: XFree 4.1.0
> Xwindows manager: KDE 2.x
> TclTk version: tcl/tk 8.3
> grass downloaded at: Baylor site
> grass binary for platform: I compiled the sources myself
> grass sources source: no, I got a source code package from the server, 
> 5.0.0pre2
> c compiler name: gcc
> 
> Anything to do with floating point raster maps with null map on a DEC Alpha 
> causes a 
> floating point exception... FIX taken from source of Grass 4.2.1 with FP + 
> NULL patches is to not use NaN to mark nulls in floating point maps but 
> rather to use FLT_MAX...

Can you try compiling with the "-mieee" switch, e.g.

	CFLAGS=-mieee ./configure ...

The "gcc" Info file suggests that the Alpha's floating-point support
takes some shortcuts, which result in NaN and infinity not working:

`-mieee'
     The Alpha architecture implements floating-point hardware
     optimized for maximum performance.  It is mostly compliant with
     the IEEE floating point standard.  However, for full compliance,
     software assistance is required.  This option generates code fully
     IEEE compliant code _except_ that the INEXACT FLAG is not
     maintained (see below).  If this option is turned on, the CPP
     macro `_IEEE_FP' is defined during compilation.  The option is a
     shorthand for: `-D_IEEE_FP -mfp-trap-mode=su -mtrap-precision=i
     -mieee-conformant'.  The resulting code is less efficient but is
     able to correctly support denormalized numbers and exceptional
     IEEE values such as not-a-number and plus/minus infinity.  Other
     Alpha compilers call this option `-ieee_with_no_inexact'.

-- 
Glynn Clements <glynn.clements at virgin.net>