Thread: Please help me make this more efficient

  1. #1
    Registered User
    Join Date
    Oct 2008

    Please help me make this more efficient


    I've written a function which removes any punctuation from around a word. For Example:
    input           output
    hello!          hello          foo
    ?they're...  they're
    My function looks like this:
    void cleanWord(char **word) {
    	size_t len = strlen(*word);
    	int count = 0;
    	char *copy = *word;
    	char *temp = malloc(len);
    	if(temp == NULL) {
    		fprintf(stderr, "Memory Error\n");
    	while(*copy) {
    		if(isalnum(*copy) || (!isalnum(*copy) && isalnum(*(copy-1)) && isalnum(*(copy+1)))) {
    			temp[count++] = *copy;
    		if(count == len) {
    			increaseBuffer(&temp, &len);
    	temp[count] = '\0';
    	*word = temp;
    This is fine for a few words, but I need to process in excess of 29000 words, and my code seems to be lagging.

    Could you help me make this more efficient please?

    Thank you for your time.

  2. #2
    and the Hat of Guessing tabstop's Avatar
    Join Date
    Nov 2007
    It might be faster to not parse the whole word, but go forwards until you find a letter, and backwards until you find a letter, and copy from start to finish.

  3. #3
    Officially An Architect brewbuck's Avatar
    Join Date
    Mar 2007
    Portland, OR
    Quote Originally Posted by tabstop View Post
    It might be faster to not parse the whole word, but go forwards until you find a letter, and backwards until you find a letter, and copy from start to finish.
    I agree. And the use of malloc() should probably be avoided if possible. If there's no reason not to simply replace the word in the buffer where it already sits, that's probably better.

    Obviously, the buffer will never need to be larger than it already is, since you are only removing characters, not inserting any.
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);

  4. #4
    Registered User
    Join Date
    Sep 2006
    There's no need for strlen(), either. The length of the word is the length of the word, so you don't need to calculate it, at all. Your program will scan it letter by letter, anyway.

    while(is an alpha letter) (may need to add an apostrophe case as well)
    copy the letter

    No increase buffer, no malloc, no long muli || this || that || something else. The word ends on a space char, a comma, a period, a newline.

    I'm not sure but I believe that isalpha can do most of this.

    I wouldn't go backwards and forwards however - just forward.

  5. #5
    Algorithm Dissector iMalc's Avatar
    Join Date
    Dec 2005
    New Zealand
    is the same as
    which is just as well since
    would be a bug. In this case though, you can just write
    You're also not malloc-ing enough space - you forgot to add one for the null terminator! Thus you're causing increaseBuffer to be called when it shouldn't be - just to add the null!
    You shouldn't need to check for the need to increase the buffer size as you're only removing chars, never adding them.

    It is wrong to be allocating a buffer for each individual word though anyway. That's my main concern. You should either do the whole thing in-place, or put all the resulting trimmed words into a single secondary buffer, allocated to the same size as the buffer the words are coming from, at the start. If you put the whole lot into a secondary buffer then the buffer you read from should be passed as const.

    So in order to make this function fast, it involves modifying the calling code as well.
    Anything else is like trying to come up with a more efficient sprinkler design when the problem is that there is a kink in the hose leading to it.
    Last edited by iMalc; 01-23-2009 at 12:29 AM.
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  6. #6
    Registered User
    Join Date
    Oct 2008
    ispunct() function could capture all the punctuations though...

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