If you have the time can you explain me a little these lines:
Code:
B = A + OFFSET(3, 2, 0);
C = B + OFFSET(3, 4, 0)
It's the same as B = A + (3*2). Just reusing my code.
Quote:
Also why its wrong with the 3 shmat() functions?
shmat() always gives you the same memory for the same ID -- that's what lets you share it between processes, you get the same memory.
Code:
// process 1
int *mem=shmat(...);
mem[0]=0xdeadbeef;
// process 2
int *mem=shmat(...);
printf("%d\n", mem[0]); // should print deadbeef if process 2 runs after 1
Modify it in one process and it gets modified in the other.
The idea's the same here, except you were using the same segment in the same process three times. It's not like malloc(), where you get new memory each time. Modify A and you modify B and C.
If you want three different segments, you need 3 different IDs. Or you can just use different memory in the same segment, like I did.
To avoid that, I use different areas of the same segment for different matrices. It's sort of like this:
Code:
int bigarray[]={1, 2, 3, 4, 5, 6, // 6 elements
12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, // 12 elements
0, 0, 0, 0, 0, 0, 0, 0 // 8 elements
};
int *A=bigarray; // Starts at element 0
int *B=A+(2*3); // Starts at element 6
int *C=B+(3*4); // Starts at element 18
Quote:
In another program i made where A and B were read by a .txt file the arrays are correct.
I couldn't tell you what your other program was doing. I can't see your computer from here.
Last edited by Corona688; 12-05-2011 at 05:57 PM..
But can't i just use the easy way with arrays, like that:
Code:
...
int A[2][3];
A=(int *)shmat(id,NULL,0);
...
I googled before i start the project and i found that arrays can be saved only with this way in shared memory.
If i could save them in the easy way that would be very helpful for my project.
They are going to be in fixed sized during the program...
In fact i read their size from the .txt and also their contents from i, so they are going to be like that:
Code:
struct shared {
int A[l][m];
int B[m][n];
int C[l][n];
};
So maybe with the struct i'll do the job.
I'll try it thanks!
They are going to be in fixed sized during the program...
In fact i read their size from the .txt and also their contents from i
That's mutually exclusive.
If they're fixed in size, they don't change and therefore can't be set at runtime.
Quote:
so they are going to be like that:
Code:
struct shared {
int A[l][m];
int B[m][n];
int C[l][n];
};
That won't work. l, m, n have to be constant numbers. That's why I asked whether they ever change.
---------- Post updated at 05:00 PM ---------- Previous update was at 04:51 PM ----------
You can do something like this:
Code:
#define A(R,C) a[(a_columns*R)+C]
#define B(R,C) b[(b_columns*R)+C]
#define C(R,C) c[(c_columns*R)+C]
int main(void)
{
int a_columns=3, a_rows=2;
int b_columns=4, b_rows=3;
int c_columns=4, c_rows=2;
int *a=shmat(...);
int *b=a + (a_rows * a_columns);
int *c=b + (b_rows * b_columns);
for(i=0; i<2; i++)
for(j=0; j<3; j++)
A(i, j)=x++;
}
Or this:
Code:
// Cheap substitution trick.
// ARR(zzz, R, C) becomes zzz[(zzz_columns * R) + C]
// So this won't work unless a zzz_columns variable actually exists.
#define ARR(NAME,R,C) NAME[(NAME ## _columns*R)+C]
// ARR_SIZE(yyy) becomes (yyy_columms * yyy_rows)
// so yyy_columns and yyy_rows need to exist somewhere if you do that!
#define ARR_SIZE(NAME) (NAME ## _columns * NAME ## _rows)
int main(void)
{
int A_columns=3, A_rows=2;
int B_columns=4, B_rows=3;
int C_columns=4, C_rows=2;
int *A=shmat(...);
int *B=A+ARR_SIZE(A);
int *C=B+ARR_SIZE(B);
for(i=0; i<A_rows; i++)
for(j=0; j<A_columns; j++)
ARR(A, i, j)=x++;
}
these are my programs but i get this error at both:
Code:
main.c: In function ‘main':
main.c:33:22: error: called object ‘a' is not a function
main.c:43:22: error: called object ‘b' is not a function
main.c:115:34: error: called object ‘c' is not a function
HI,
i am trying to multiply 2 2D arrays (a,b) using fork.
The answer will be at c.
Each child have to calculate 1 row of c.
The code is right, as i think of it, with no errors but i dont get the correct c array...
I think there is maybe a mistake in i dimension ...
Anyway, here is the code:
... (16 Replies)
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i=0
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let i++
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im sorry for my english .
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start_interface_func()
{
i=0
for interface_chk in 11 71 73 72 12 47 48 49 50 20 23 24 25 46 21 22 27 28... (5 Replies)
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Hi
I have two arrays:
arr1 = (demo demo2 demo3 demo4 demo5)
arr2 = (demo2 test demo)
I want to check that the values the "arr2" are present in "arr1"
Example
arr1 = (demo demo2 demo3 demo4 demo5)
arr2 = (demo2 test demo)
Output: Error
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Hi
$ a=10 ; b=2
$ expr $a + $b
12
$ expr $a - $b
8
$ expr $a / $b
5
$ expr $a * $b
expr: syntax error
Any idean why I am getting this error only when multiplying two numbers. Whats the exact syntax?
Thanks a lot to all in advance
CSaha (5 Replies)
12-05-2011
