How do you read a large ( 100Mb) 3-D matrix from a file and make sure that you keep only one copy of it within the LV program for future use?

Question

I have to deal with large 3-D, I16 matrices that are stored in files. This data represents the density of an object at a sample point in 3-D space. I need to be able to display a 2-D section through the cube in an Intensity Chart. Since I want to update images in the intensity chart in real time to show different sections on demand I cannot adopt the approach of reading a section from the file when required - the I/O time assocaited with the disk read is way to long.
The solution, is to keep EXACTLY one copy of the entire data set in memory at all times and then just get the required section on demand.
This changes the disk I/O time to a memory access time, which is fast enough for my puposes.
Here is the problem. Since the matrices are so large, I want to be very sure that I only keep one in copy of the data in memory. After a couple of weeks discussioin with Tech Support, and the development of several sample programs, they have agreed that it is not possible to do it with less than two copies of the data in memory.
This additional memory requirement is a real problem for me and I am hoping someone is ingenious enough to come up with a way of doing it with only one.
I can send a sample program illustrating the problem if necessary.
Many thanks.

Answer 1

Jean Pierre,
Thanks for your reply - most kind of you to take the time. But.....
This is exactly what I thought, and is similar in concept to the way I wrote my code. But it doesn't work. I modified you llb slightly by setting the variables to be I16's and setting the default array size to 54,000,000 and the default action to be initialize. ( I'll enclose a copy of my modified llb for you.)
Here's what happened. I start the windows task manager, loaded LV and the program and looked at the memory shown in the task manager. It shows about 28Mb before I start to run the program. I then single step through the program. When it gets to the output of the Initial Array the memory usage jumps to about 134Mb, indicating the creation of the first copy of the array. As you continue single stepping it jumps to 239Mb as you leave the Case loop and head for the Shift Register. This memory does not drop down again.
After talking with Platinum Tech Support, they agree and tell me that they cannot see a way to have just one copy of the array. That's why I posted it on the message board to see if there was anyone out there who had come up with an ingenious solution. It seems to be a serious limitation to labview.
Let me know what you think.
Thanks once again.
Attachments:
HugeArrayMod.llb ‏92 KB