I am going to rewrite my program to use explicit loops to avoid these
really large arrays. I will write out the data to a separate file for
each of the rows of the larger array (this will be slow, but might
work). I still want to use mapped files to work with the row files
though, it will probably be much faster that (3!:0)~ (3!:1)?
But does anyone know why the code below fails though? I want to
calculate the size of the mapped file inside a verb. The two pieces of
code below should both work but if I calculate "size" rather than just
assigning it the map_jmf_ verb does not work.
I don't want to try the write code to read/write a large mapped file
in segments that fit into the physical memory because I don't think I
am good enough at J or understand enough about VAS and mapped files to
do that.
size =. 8192 NB. just assign the size
bigfn =. jpath '~temp\big.jmf'
createjmf_jmf_ bigfn;size
map_jmf_ 'bigvar';bigfn
bigvar =. size # 'x'
unmap_jmf_ 'bigvar'
0
size =. 2 * 2 %~ 8192 NB. just an example of calculating size
bigfn =. jpath '~temp\big.jmf'
createjmf_jmf_ bigfn;size
map_jmf_ 'bigvar';bigfn
|bad jmf header: assert
| 'bad jmf header' assert 0[free fh,mh,fad
Thanks,
Matthew.
PS thanks for the links Bjorn.
On Mon, Nov 17, 2008 at 11:19 AM, Chris Burke <[EMAIL PROTECTED]> wrote:
> Matthew Brand wrote:
>> I originally asked this on general as part of a discussion about using
>> J64 on Linux under VMWare Fusion on a MacBook Pro, but it might be
>> better suited to the programming forum.
>
> Yes - questions on using J should go to programming; questions on
> installing J to general.
>
>> In Ubuntu, System Monitor->Resources->Memory I have got 2.8 GB of free
>> memory indicated. Should I be able to create a 2GB mapped file inside
>> the 64 bit VAS? I.e. should the code below work? Also, does the amount
>> of free memory matter anyway? Can mapped files be larger than the
>> amount of physical memory? I thought that with J64 I would be able to
>> (if I had enough disk space and time) create a mapped variable of size
>> 2^64 bytes, is that untrue?
>
> The jmf script in the current library supports both 32 and 64 bit.
>
> However, jmf maps the entire file and this requires that the file size
> be at least no greater than the available RAM. Since you need some RAM
> for the rest of your work, the maximum mapped file size is usually quite
> a bit less than available RAM.
>
> Since you could not create a mapped variable of size larger than RAM,
> then for larger mapped files, you would need to modify the map verb to
> map only a part of the file.
>
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>
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