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Top Forums Shell Programming and Scripting script to add numbers is slow Post 302300316 by CRGreathouse on Monday 23rd of March 2009 09:10:19 PM
Old 03-23-2009
Lightbulb

That is an improvement. I timed it at 2m13.027s doing 5000x5000. But there's a tenfold improvement with a direct translation to C (11.885s):
Code:
#include <stdio.h>

main(int argc, char *argv[])
{
    int height = atoi(argv[1]);
    int width = atoi(argv[2]);
    int i = width * height - width - 1;
    int k = width - 1;
    int j;
    for (j = 0; j < i; j++) {
        if (j == k) {
            //printf("%i\n", k + width);
        } else {
            int tmp = j + width;
            printf("4 %i %i %i %i\n", j, j + 1, tmp + 1, tmp);
        }
    }
    return 0;
}

An optimized version might be even better.
 

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RBASH(1)						      General Commands Manual							  RBASH(1)

NAME
rbash - restricted bash, see bash(1) RESTRICTED SHELL
If bash is started with the name rbash, or the -r option is supplied at invocation, the shell becomes restricted. A restricted shell is used to set up an environment more controlled than the standard shell. It behaves identically to bash with the exception that the follow- ing are disallowed or not performed: o changing directories with cd o setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV o specifying command names containing / o specifying a filename containing a / as an argument to the . builtin command o specifying a filename containing a slash as an argument to the -p option to the hash builtin command o importing function definitions from the shell environment at startup o parsing the value of SHELLOPTS from the shell environment at startup o redirecting output using the >, >|, <>, >&, &>, and >> redirection operators o using the exec builtin command to replace the shell with another command o adding or deleting builtin commands with the -f and -d options to the enable builtin command o using the enable builtin command to enable disabled shell builtins o specifying the -p option to the command builtin command o turning off restricted mode with set +r or set +o restricted. These restrictions are enforced after any startup files are read. When a command that is found to be a shell script is executed, rbash turns off any restrictions in the shell spawned to execute the script. SEE ALSO
bash(1) GNU Bash-4.0 2004 Apr 20 RBASH(1)
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