Smart-Basic Array Order

[MarkP]

I have no idea whether the Apple CPU chips in the iphone and ipad devices benefit from cache memory, but just in case they do, I wanted to set the order of array indexes properly to take advantage of memory caching, especially with using large 3-dimensional arrays.

To do this, I needed to determine whether arrays in smart BASIC are ordered in "column-major-order" (first index causes memory-contiguous elements) or "row-major-order" (last index causes memory-contiguous elements).

Since SB shields the programmer from memory layout information, I figured I'd use "debug" to determine the layout of 3-dimensional arrays.

To my surprise, based on the order that debug indicates, SB is neither column-major nor row-major.

Try the following code:

option base 1
n=0
dim a(4,4,4)
for x=1 to 4
for y=1 to 4
for z=1 to 4
n+=1
a(y,z,x)=n 'NOTE THIS ORDER
next z
next y
next x
debug pause

Can anyone assist with this?
I expected either (x,y,z) or (z,y,x), but NOT (y,z,x).

[Mr. Kibernetik]

Internally smart BASIC uses column-major ordering.
But you cannot detect this by your BASIC program because BASIC language does not use pointers. Also don't forget that smart BASIC uses complex numbers, not real numbers.

[MarkP]

Yes, I am aware that I cannot detect the array ordering by myself. (I tried using debug) However, it is still good to know so that I can properly order the array indexes so that sequential reading of the array is via the major index to allow the processor to cache data accesses, if possible.