Improve company productivity with a Business Account.Sign Up

x
?
Solved

Declaration of array

Posted on 1998-08-21
2
Medium Priority
?
275 Views
Last Modified: 2010-04-15
I have been declaring my array in the fashion shown in the code segment below and the max size for my PC is 64x64. What's wrong with my codes? How can I increase the sizes of the arrays to 512x512? Do I have to deal with setting the buffer size or virtual memory?

My declaration of array is as follow:

#define HEIGHT 32
#define WIDTH 32

short  x,y,ro[HEIGHT][WIDTH],go[HEIGHT][WIDTH],bo[HEIGHT][WIDTH];
short  rq[HEIGHT][WIDTH],gq[HEIGHT][WIDTH],bq[HEIGHT][WIDTH];
float  rn[HEIGHT][WIDTH],gn[HEIGHT][WIDTH],bn[HEIGHT][WIDTH];
float  rq2[HEIGHT][WIDTH],gq2[HEIGHT][WIDTH],bq2[HEIGHT][WIDTH];


The way I use the array :

  for (x=0;x<HEIGHT;x++)
     {
       for (y=0;y<WIDTH;y++)
          {
              Infile>>ro[x][y]>>go[x][y]>>bo[x][y];

              rn[x][y]=ro[x][y]/255.0;
              gn[x][y]=go[x][y]/255.0;
              bn[x][y]=bo[x][y]/255.0;

              rq[x][y]=ro[x][y]*15/255;
              gq[x][y]=go[x][y]*15/255;
              bq[x][y]=bo[x][y]*15/255;

              rq2[x][y]=rq[x][y]/15.0;
              gq2[x][y]=gq[x][y]/15.0;
            bq2[x][y]=bq[x][y]/15.0;

       }
  }

Can I have an example of more efficient implementation of arrays ?
0
Comment
Question by:peiyoke
2 Comments
 
LVL 8

Accepted Solution

by:
Answers2000 earned 150 total points
ID: 1252243
Depends on the compiler.

Assuming DOS or Win3.1 (you mention code segment which implies you are compiling small or medium model on one of these)
64*64*2 (array of shorts) = 8192 bytes
64*64*4 (array of floats) = 16384 bytes

A segment in these environments is 64K.

The easiest solution is to change to LARGE model (in your compiler options).  In DOS/Win3.1 any single variable can be up to 64K in these models.

so
512*512*2 (shorts) = 524288 bytes
512*512*4 (floats) = 1048576 bytes.

Unfortunately this still doesn't fit in one segment.

What you have to is
1. Allocate the memory (GlobalAlloc then GLobalLock in Windows, or compiler specific huge-malloc function in DOS)
2. Cast the pointer to the of the array into a huge pointer
3. Calc position in the array, something like
long offset = (long)( column * sizeof(short) ) + (long)( row * 512 * sizeof(short) )
item_address = start_of_memory + offset
(substitue sizeof(float) for the float arrays)).
4. Access memorys in the array by doing
*item_address = value
or
value = *item_address ;
5. When done free the memory (GlobalUnlock then GlobalFree in Windows, or free in DOS)

For DOS you will need also need a DPMI (DOS Protected Mode Interface) capable compiler or a compiler than knows about DOS extenders.

BTW if you have read in an old Petzold (Win 3.1 version) that Large version is bad news, this only applies to MS C versions 5.1 and 6 - it is fixed in MS C 7.0, MS C 8 and all versions of Visual C and Borland C.

If you switch to NT, Win95 or UNIX you will not have these problems and can declare arrays any size.


0
 
LVL 11

Expert Comment

by:alexo
ID: 1252244
For DOS or Windows 3.x try:
    huge float rn[HEIGHT][WIDTH], ...
    ^^^^^
0

Featured Post

Managing Security & Risk at the Speed of Business

Gartner Research VP, Neil McDonald & AlgoSec CTO, Prof. Avishai Wool, discuss the business-driven approach to automated security policy management, its benefits and how to align security policy management with business processes to address today's security challenges.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Have you thought about creating an iPhone application (app), but didn't even know where to get started? Here's how: ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Important pre-programming comments: I’ve never tri…
Windows programmers of the C/C++ variety, how many of you realise that since Window 9x Microsoft has been lying to you about what constitutes Unicode (http://en.wikipedia.org/wiki/Unicode)? They will have you believe that Unicode requires you to use…
The goal of this video is to provide viewers with basic examples to understand how to use strings and some functions related to them in the C programming language.
The goal of this video is to provide viewers with basic examples to understand how to create, access, and change arrays in the C programming language.

608 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question