ben / somethingmodern.com wrote:
> Does anyone have experience with using Ruby for analysis (*lots* of
> maths), on a machine with a ridiculous amount of RAM? For example, a
> hip 64-bit Linux kernel on a machine with 32 or 64 GB of physical RAM.
> 
> Are there any "gotchas" I should be aware of? Would all the RAM be
> addressable by a given Ruby process? Or would I still have to be
> forking a number of processes, each allocated a bit of the address
> space (blech)?
> 
> Thanks, oh Ruby masters.

1. Again, you can contact me off list for some ideas ... without knowing 
your goal, it's difficult for me to know what steps you should take to 
reach it.

2. Assume a properly working state-of-the-art 64-bit dual-core AMD or 
Intel hardware platform with 64 GB of RAM and an appropriate SAN for 
storage from a major vendor like IBM. That severely limits your OS 
choices; last time I looked you need to be running either RHEL or SUSE 
Enterprise Linux. I don't know about the other vendors, but IBM has a 
marvelous document on performance tuning humongous servers at

http://www.redbooks.ibm.com/redbooks/pdfs/sg245287.pdf

3. OK, now you've purchased a high-end server and a *supported* 
enterprise-grade Linux, and you want to do some serious number crunching 
on it, and you want to do it in Ruby, possibly augmented by libraries in 
C, Fortran or assembler for speed. You will need to recompile 
*everything* -- Ruby, the math libraries, and the compiler itself -- to 
use 64-bit addressing. There are some hacks and workarounds, but pretty 
much this is required. If you end up with an Intel server, you might 
want to have a look at the Intel compilers instead of GCC. Intel also 
has some highly-tuned math libraries, as does AMD.

My point here is that you are "exploring" realms in Ruby that are 
"usually" addressed using "more traditional" techniques, so you're going 
to need to do a fair amount of testing. That kind of server costs a lot 
of money, and for that kind of money, you'll get lots of support from 
the vendor, coupled with strong incentives to do your job in ways that 
are tested and proven to work and supported by said vendor.That may or 
may not include Ruby, and if it does include Ruby, it may or may not 
involve a small number of monolithic Ruby scripts directly addressing a 
large address space.

There is a lot of help available on the Internet from people like me who 
love challenges like this. :)