Trying to get a NN code going

[Richard A. O'Keefe]

As an example for a 1 week C course I taught recently ("for", not "in";
I only thought of it just afterwards, but _next_ time...) I took a
simple Neural Network program written by someone who is an expert in
the field and speeded it up by a factor of 2.5, basically by writing
the kind of clean C any APL fan would produce (:-).

It occurred to me:  why not rewrite it in Clean?  It ought to go rather
nicely.  The improved C version gets its performance by
 - massive (automatic) inlining (C compilers have got quite smart)
 - *amazing* loop unrolling and the resulting
 - scheduling to take advantage of superscalarity
Now, a Clean compiler ought to be able to beat the pants off any C
compiler at inlining, but it is not at all clear to me that it's likely
to do the kind of loop unrolling, or even scheduling, that is needed.

My strategy was
 1. Develop list based translation with the test data in the source code.
 2. Revise it to read the data from a file at run time.
 3. Revise it again to use {#Real} instead of [Real] for vectors.

However, I'm stuck at step 1.
On a SPARCstation 5 running Solaris 2.6.1, Clean 1.3 is happy with the
program, even the test data (which is about 1400 lines containing
9320 numbers).  I compiled it with -h 80M -s 4M.  The result ran for
1 second of user time, 12 seconds of system time, and died with a
segmentation violation.

What do UNIX Clean programmers do when they get a segmentation
violation?  How do I track this down to its cause?

I hoped that the Macintosh version might be a bit better, but when
I try to _compile_ the program on a PowerMac 7600/120 running MacOS 8.1,
an Errors window pops up, containing

    Fatal Error in comsupport:TH_Alloc "Insufficient Memory"

Trouble is, I can't tell whether this means the Clean _IDE_ needs to
be resized or the Clean _compiler_, nor by how much.  I note that the
compiler is still running (it's in the switcher menu) and have no idea
what I'm supposed to do about that.

Replacing the timing test data with toy (XOR) data,
the program gets a 'rule X in module Y does not match' error.
This applies to both the SPARCstatation and the PowerMac.
I know what the immediate cause is (calling an elementary matrix
update function with arguments of the wrong sizes), but I don't
know _where_ it is happening in the program or what the sizes
actually are.

This is the first Clean program I've had where the compiler hasn't told
me about all the bugs, and I'm wondering how other Clean programmers go
about debugging their code.  In SML, I'd just whack in a few print
commands and be away laughing.

I'm going to be teaching a functional programming class again this
semester, and I'd like to hand this out _working_ in about a week...