[Radiance-general] compiling Radiance 64-bit?

[Lars O. Grobe]

Hi list!

>> Correct and radiance gets no where near 2GB. (At least I run out of
>> CPU long before the model is that big.)
> 
> I totally agree there: It's still the CPU speed that's limiting.

I have a model that is getting close to 2GB here.

> I am not sure how 'bitty' the floating point values are that RADIANCE
> calculates. If they are 64-bit long, then you can actually expect a speed
> improvement, me thinks.

Most floating point values are doubles, thus 64bit. Still, the whole
64bit-point is about address pointers. All the old "32-bit" cpus support
calculations on 64bit values - double floats are not that new (a SSE2
unit as found in recent 32bit intel cpus can even perform calculations
on 2 64bit values at once). So we are only talking about increasing the
amount of addressable memory here.

Correct me if I am wrong. I am not a cpu expert. But do not compile
Radiance in 64 bit if you do not need memory. If you do, take a look at
compilers. E.g. Sun has a free compiler that is known to produce 64 bit
code that can compete with 32 bit in speed.

Lars.
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