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writing file, memory not released
Discuss writing file, memory not released in the C Programming forum on Dev Shed.
writing file, memory not released C programming forum discussing all C derivatives, including C#, C++, Object-C, and even plain old vanilla C. These languages are low level languages, and used on projects such as device drivers, compilers, and even whole computer operating systems.
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June 20th, 2005, 08:51 AM
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writing file, memory not released
i use redhat linux, gcc compiler. in my code, i write out data at certain time interval with different file names, and i use fopen and fclose after each write-out. but when i check the memory usage, it keeps increasing after each call to output the data. ??? any help is appreciated... thanks.
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June 20th, 2005, 08:53 AM
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show code. Are u allocating memory dynamically?
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June 20th, 2005, 10:06 AM
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writing file, memory not released
at the beginning, i allocate variable q dynamically. and q is kept throughout the running process (no free and re-allocate is done). basically the code:
PHP Code:
main()
{
allocate q[isize][jsize]
time loop
do something with the data
if plot_time is reached
plotdata() //write out q
end time loop
}
void plotdata()
{
FILE*fplot
fplot = fopen(filename,"w") //filename is different for different time
writeout data
fclose(fplot)
}
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June 20th, 2005, 10:11 AM
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This pseudo-code does not help at all... what does plotdata do? allocating by q[n][p] is NOT called dynamic allocation. Dynamic allocation uses malloc() or new...
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June 20th, 2005, 12:35 PM
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oh...i just put allocate q[n][m]... but in fact, i use malloc to allocate memory for q and this is done correctly, i've checked.
in plotdata()... just writing out q to a data file using
fprintf(fplot,"...."); and nothing else. then the file is closed after it's done.
could this have something to do with the compiler?
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June 20th, 2005, 12:57 PM
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Contributing User
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Quote: | Originally Posted by onebug could this have something to do with the compiler? | Generally not. I'd post your actual code first.
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June 20th, 2005, 01:46 PM
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i cut out some unnecessary details (ex: initializing some vars, etc.). okay here goes:
PHP Code:
int main(void)
{
int iter;
double tcount;
iter = 0;
mem_alloc();
while (time_current < time_end) {
iter++;
time_current += dtmin;
tcount += dtmin;
if (tcount >= tplot) {
tcount = tcount - tplot;
plotdata(iter);
}
}
return 0;
}
PHP Code:
void plotdata(const int iter)
{
short i,j;
FILE *fplot;
char filename[20];
sprintf(filename,"data/%05d.dat",iter);
fplot = fopen(filename,"w");
for (j = 0; j < NYMAX; j++)
for(i = 0; i < NXMAX; i++) {
fprintf(fplot,"%15.10e %15.10 %10.3e \n",x[i],y[j],q[i][j][0]);
}
fclose(fplot);
}
PHP Code:
void mem_alloc()
{
short i,j,nvars;
nvars = 2;
q = (double ***) malloc(NXMAX*sizeof(double **));
for (i = 0; i < NXMAX; i++) {
q[i] = (double **) malloc(NYMAX*sizeof(double *));
for (j = 0; j < NYMAX; j++) {
q[i][j] = (double *) malloc(nvars*sizeof(double));
}
}
}
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June 20th, 2005, 02:04 PM
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I honestly don't see any memory leaks except in ur mem_alloc() function which is called only once. Perhaps they're in the "unnecessary details"....
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June 21st, 2005, 06:57 AM
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thanks anyway.
i am almost 100% sure it's not in the "unnecessary details". anyone else has any suggestion? 
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June 21st, 2005, 07:03 AM
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Wiser? Not exactly.
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Join Date: May 2001
Location: Bonita Springs, FL
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How much does the memory increase by? Does the amount of increase match up w/ any amount of data that you know might be written/created by the program?
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June 21st, 2005, 11:16 AM
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i don't have to code in front of me to find out exactly. but from memory, it seems to increase by about 100MB and i think this is related to the size of variables being written out (q). (i make a quick calculation and it's about the same order of magnitude)
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