The Problem about clearing the system cache

Question

Hi, there!
I'm trying to draw a lot of image in iPhone programming.
I used [UIImage imageNamed].
but it doesn't clear immediately the system cache.
At last it occurs the out of memory.
So I thought using imageWithContentsOfFile, but it works very slowly.
Does anybody know how to clear the system cache?

Answer 1

Read Position.flx can execute much faster than 5 ms but as it reads a register that is updated every 5 ms on the board, it reads the same value multiple times.
To get around this problem there are two methods:
Buffered High-Speed-Capturing (HSC)
With buffered HSC the board stores a position value in it's onboard buffer each time a trigger occurrs on the axis' trigger input. HSC allows a trigger rate of about 2 kHz. That means, you can store a position value every 500 µs. Please refer to the HSC examples. You may have to look into the buffered breakpoint examples to learn how to use a buffer, as there doesn't seem to be a buffered HSC example available. Please note that you need an external trigger-signal (e. g. from a counter of a DAQ board). Please note that the amount of position data that you can acquire in a single shot is limited to about 16.000 values.
Buffered position measurement with additional plugin-board
If you don't have a device that allows you to generate a repetitive trigger signal as required in method 1.), you will have to use an additional board, e. g. a PCI-6601. This board provides four counter/timers. You could either use this board to generate the trigger signal or you could use it to do the position capturing itself. A PCI-6601 (or an M-Series board) provides can run a buffered position acquisition with a rate of several hundred kHz and with virtually no limitation to the amount of data to be stored. You could even route the encoder signals from your 7350 to the PCI-6601 by using an internal RTSI cable (no external wiring required).
I hope this helps,
Jochen Klier
National Instruments