Problem with progress code

This is a discussion on Problem with progress code within the C Programming forums, part of the General Programming Boards category; Code: while(1) { c = fgetc(fo); if(c == EOF){ break; } else{ c = c + 'c' + 'd' - ...

  1. #1
    Cogito Ergo Sum
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    Problem with progress code

    Code:
    while(1) {
          
          c = fgetc(fo);
    
          if(c == EOF){
    
            break;
          }
          else{
            c = c + 'c' + 'd' - 't';
            fputc(c,fw);
            cnt++;
            if(cnt % d == 0) {
              prog++;
            }
            printf(" %d%%\r", prog);
            fflush(stdout);
          }
        }
        printf(" %d%%\n", prog);
        printf("DONE!\n");
    When the lines of code that are in red are removed, the program works very quickly, but when it's kept, it works extremely slowly.

    This is part of a program that encrypts characters from a file and then outputs it into another file. I created this progress meter to show how long it takes when encrypting. When the file size is small, < 5kb, there is no problem. But when it's 3MB, then it takes upto 5 minutes when the progress meter is there, when I remove it, it takes only 5 seconds.

    I don't see what the problem with the code is.
    =========================================
    Everytime you segfault, you murder some part of the world

  2. #2
    CSharpener vart's Avatar
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    use print only when the new percent value is different from the printed earlier one
    printf with fflush takes a long time - so make it only when really necesary
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  3. #3
    Cogito Ergo Sum
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    How do I do that ^ ?

    I removed fflush, but that makes no difference.
    =========================================
    Everytime you segfault, you murder some part of the world

  4. #4
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    Does your code "know" when progress has changed, by any chance?

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  5. #5
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    I think it has to do with
    Code:
    if(cnt &#37; d == 0) {
    ...
    you're essentially calculating the cnt variable to zero with ==. Try just using =
    hope that helps.

  6. #6
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    Quote Originally Posted by MikeyIckey View Post
    I think it has to do with
    Code:
    if(cnt % d == 0) {
    ...
    you're essentially calculating the cnt variable to zero with ==. Try just using =
    hope that helps.

    No, = is an assignment. I'm not trying to assign it, I'm trying to find a remainder with modulus.
    =========================================
    Everytime you segfault, you murder some part of the world

  7. #7
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    Quote Originally Posted by matsp View Post
    Does your code "know" when progress has changed, by any chance?

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    Yea, when cnt % d == 0
    =========================================
    Everytime you segfault, you murder some part of the world

  8. #8
    Jack of many languages Dino's Avatar
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    Code:
    while(1) {
          
    	c = fgetc(fo);
    
    	if (c == EOF){
    		break;
    	}
    	// As a matter of practice, you don't need an else here.
    	else {
    		c = c + 'c' + 'd' - 't';
    		fputc(c,fw);
    		cnt++;
    		if (cnt % d == 0) {
    			prog++;   // indicator changed... therefore...
    			printf(" %d%%\r", prog);    // update indicator only here
    			fflush(stdout);                 
    		}
    	}
    }
    printf(" %d%%\n", prog);
    printf("DONE!\n");
    Mac and Windows cross platform programmer. Ruby lover.

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  9. #9
    Jack of many languages Dino's Avatar
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    You could also create another variable to hold this result since it never changes, and there's no need to recalculate it for EVERY STINKING CHARACTER.

    Code:
    int delta = 'c' + 'd' - 't';
    Mac and Windows cross platform programmer. Ruby lover.

    Quote of the Day
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    Amen brother!

  10. #10
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    Quote Originally Posted by JFonseka View Post
    Yea, when cnt % d == 0
    Right, so my point being that you then only need to print the updated progress when it changes, as Todd posted below - I wanted you to figure that part out yourself.

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  11. #11
    Cogito Ergo Sum
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    I can't believe I didn't see that mistake...

    Thanks
    =========================================
    Everytime you segfault, you murder some part of the world

  12. #12
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    Quote Originally Posted by Todd Burch View Post
    You could also create another variable to hold this result since it never changes, and there's no need to recalculate it for EVERY STINKING CHARACTER.

    Code:
    int delta = 'c' + 'd' - 't';
    Although the compiler can calculate the sum/difference of a few constants in that simple way. And even if it didn't, it would still disappear in the noise in a profile, compared to fgetc()/fputc() - I'm sure the processor can add/subtract in something like 3 clock-cycles (on a reasonably modern processor - 486 or better), whilst fgetc() is bound to take a few hundred cycles.

    --
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    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  13. #13
    Jack of many languages Dino's Avatar
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    true.
    Mac and Windows cross platform programmer. Ruby lover.

    Quote of the Day
    12/20: Mario F.:I never was, am not, and never will be, one to shut up in the face of something I think is fundamentally wrong.

    Amen brother!

  14. #14
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    Quote Originally Posted by JFonseka View Post
    No, = is an assignment. I'm not trying to assign it, I'm trying to find a remainder with modulus.
    sorry I was really exhausted when I posted that.

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