[Haskell-cafe] Where's the problem ?

Rome roman.kraehling at unibw-muenchen.de
Wed Jul 4 10:30:55 EDT 2007

Hi everyone,

I write a program for fast online multiplication, this means, leading digits
are computed first, so this program is able to handle real numbers. 

My program and Source-Code is available under
http://www.romeinf04.de http://www.romeinf04.de 

but only with german comments, because this is my master thesis.

Now the problem:
My program computes using the schoenhage-strassen multiply-subroutine the
output everytime only until the 32777th Digit, but then it holds without an
error message. Windows Task manager tells me CPU Usage 100% and Memory
Allocation is increasing.
Profiling told me, the function Algorithm.resultOfMult is using this memory.
To compute the 32777th digit, my program needs several digits of the
input-numbers including the 32800th.
I'm using GHC 6.6.1 with option -O2 to compile.

Output is row-wise by an IO-function, calling itself recursively with
updated parameters, hte output looks like:

dig11 dig21 --> res1
dig12 dig22 --> res2
dig12 dig23 --> res3
. and so on

If I use the Naive-Multiply-Subroutine, the problem occurs at the 16392th

A friend of mine compiled it under Linux and got:
32779 :  1   1 ---32776-->  0
32780 :  1   0 ---32777--> -1
Main: Ix{Integer}.index: Index (32766) out of range ((0,32765))

If I convert every Integer into Int and use instead of the generic list
functions the prelude-list functions, it works.
I don't have any idea, where the problem might be...



Please excuse my english writing, I'm from Germany.
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