Making Revolution faster with really big arrays

[Frank D. Engel, Jr.]

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Rev's arrays are associative.  When using an array with an index like 
[X, Y, Z], you are really saying, make a string whose contents are X, 
Y, and Z separated by commas, then use that as the index for the array. 
  These array indexes take up memory, along with your data.  In fact, 
depending on what type of data you are trying to process, they likely 
take up more.  Even without the overhead of the structures used to 
represent the arrays, your array will likely take up well over 2GB of 
RAM.  On a 32-bit system, you are normally limited to either 2GB or 3GB 
of memory per process (almost always 2GB, but some Windows versions -- 
mostly server versions -- can be configured for 3GB per process), so 
that array would take more memory than all of your data PLUS Revolution 
PLUS your stack(s) PLUS some code used by the runtime libraries from 
the OS ... you get the idea.

You'll never be able to fit that entire array into memory *as an array* 
in Rev.

Have you considered loading it into a single string and parsing the 
data inline while managing it in your code?

Try something like:

put URL "file:/path/to/MyFile.txt" into x

Then parse the data from x:

put word 1 of item 2 of line 6 of x into y

And so on...


On Apr 12, 2005, at 4:36 PM, Dennis Brown wrote:

> Hi all,
>
> I just joined this list.  What a great resource for sharing ideas and 
> getting help.
>
> I am actively writing a bunch of Transcript code to sequentially 
> process some very large arrays.  I had to figure out how to handle a 
> gig of data.  At first I tried to load the file data into a data 
> array[X,Y,Z] but it takes a while to load and processes for random 
> access and it takes a lot of extra space for the structure.  I also 
> could never get all the data loaded in without crashing Revolution and 
> my whole system (yes, I have plenty of extra RAM).
>
> The scheme I ended up with is based on the fact that the only fast way 
> I could find to process a large amount of data is with the repeat for 
> each control structure.  I broke my data into a bunch of 10,000 line 
> by 2500 item arrays.  Each one holds a single data item (in this case 
> it relates to stock market data).  That way I can process a single 
> data item in one sequential pass through the array (usually building 
> another array in the process).  I was impressed at how fast it goes 
> for these 40MB files.  However, this technique only covers a subset of 
> the type of operations I need to do.  The problem is that you can only 
> specify a single item at a time to work with the repeat for each.  In 
> many cases, I need to have two or more data items available for the 
> calculations.  I have to pull a few rabbits out of my hat and jump 
> through a lot of hoops to do this and still go faster than a snail.  
> That is a crying shame.  I believe (but don't know for sure) that all 
> the primitive operations are in the runtime to make it possible to do 
> this in a simple way if we could just access them from the compiler. 
> So I came up with an idea for a proposed language extension.  I put 
> the idea in Bugzilla yesterday, then today, I thought I should ask 
> others if they liked the idea, had a better idea, or could help me 
> work around not having this feature in the mean time, since I doubt I 
> would see it implemented in my lifetime based on the speed I see 
> things getting addressed in the Bugzilla list.
>
> The Idea is to break apart the essential functional elements of the 
> repeat for each control to allow more flexibility.  This sample has a 
> bit more refinement than what I posted yesterday in Bugzilla.
>
> The new keyword would be "access" , but could be something else.
>
> An example of the use of the new keywords syntax would be:
>
> access each line X in arrayX--initial setup of pointers and X value
> access each item Y in arrayY --initial setup of pointers and Y value
> repeat for number of lines of arrayX times --same as a repeat for each
>    put X & comma & Y & return after ArrayXY --merged array
>    next line X --puts the next line value in X
>    next item Y --if arrayY has fewer elements than arrayX, then empty 
> is supplied, could also put "End of String" in the result
> end repeat
>
> Another advantage of this syntax is that it provides for more 
> flexibility in structure of loops.  You could repeat forever, then 
> exit repeat when you run out of values (based on getting an empty 
> back).  The possibilities for high speed sequential access data 
> processing are much expanded which opens up more possibilities for 
> Revolution.
>
> I would love to get your feedback or other ideas about solving this 
> problem.
>
> Dennis
>
> _______________________________________________
> use-revolution mailing list
> use-revolution at lists.runrev.com
> http://lists.runrev.com/mailman/listinfo/use-revolution
>
>
- -----------------------------------------------------------
Frank D. Engel, Jr.  <fde101 at fjrhome.net>

$ ln -s /usr/share/kjvbible /usr/manual
$ true | cat /usr/manual | grep "John 3:16"
John 3:16 For God so loved the world, that he gave his only begotten 
Son, that whosoever believeth in him should not perish, but have 
everlasting life.
$
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