Need help optimizing the writing of a very large array and streaming it a file

Question

Hi,
I have a very large array that I need to create and later write to a TDMS file. The array has 45 million entries, or 4.5x10^7 data points. These data points are of double format. The array is created by using a square pulse waveform generator and user-defined specifications of the delay, wait time, voltages, etc. 
I'm not sure how to optimize the code so it doesn't take forever. It currently takes at least 40 minutes, and I'm still running it, to create and write this array. I know there needs to be a better way, as the array is large and consumes a lot of memory but it's not absurdly large. The computer I'm running this on is running Windows Vista 32-bit, and has 4GB RAM and an Intel Core 2 CPU @ 1.8Mhz. 
I've read the "Managing Large Data Sets in LabVIEW" article (http://zone.ni.com/devzone/cda/tut/p/id/3625), but I'm unsure how to apply the principles here.  I believe the problem lies in making too many copies of the array, as creating and writing 1x10^6 values takes < 10 seconds, but writing 4x10^6 values, which should theoretically take < 40 seconds, takes minutes. 
Is there a way to work with a reference of an array instead of a copy of an array?
Attached is my current VI, Generate_Square_Pulse_With_TDMS_Stream.VI and it's two dependencies, although I doubt they are bottlenecking the program. 
Any advice will be very much appreciated. 
Thanks
Attachments:
Generate_Square_Pulse_With_TDMS_Stream.vi ‏13 KB
Square_Pulse.vi ‏13 KB
Write_TDMS_File.vi ‏27 KB

Answer 1

Thanks Ravens Fan, using replace array subset and initializing the array beforehand sped up the process immensely. I can now generate an array of 45,000,000 doubles in about one second.
However, when I try to write all of that out to TDMS at the end LV runs out of memory and crashes. Is it possible to write out the data in blocks and make sure memory is freed up before writing out the next block? I can use a simple loop to write out the blocks, but I'm unsure how to verify that memory has been cleared before proceeding.  Furthermore, is there a way to ensure that memory and all resources are freed up at the end of the waveform generation VI? 
Attached is my new VI, and a refined TDMS write VI (I just disabled the file viewer at the end). Sorry that it's a tad bit messy at the moment, but most of that mess comes from doing some arithmetic to determine which indices to replace array subsets with. I currently have the TDMS write disabled.
Just to clarify the above, I understand how to write out the data in blocks; my question is: how do I ensure that memory is freed up between subsequent writes, and how do I ensure that memory is freed up after execution of the VI?
@Jeff: I'm generating the waveform here, not reading it. I guess I'm not generating a "waveform" but rather a set of doubles. However, converting that into an actual waveform can come later. 
Thanks for the replies!
Attachments:
Generate_Square_Pulse_With_TDMS_Stream.vi ‏14 KB
Write_TDMS_File.vi ‏27 KB