what I do is
query (count) of rows from DB
replace strings in them
write it in .csv
When 150 rows are selected in the first step, around 20sec. are needed to finish the script (csv is ready). If I bypass the second step, nothing replaces, the export is ready for ~2sec.
To replace I defined two not associative arrays: array $replace and array $rwith each with 30 elements.
Then:
str_ireplace($replace, $rwith, $value);
Probably str_replace (case sensitive) will speed the things up a little, but my goal is under 5s. What can you suggest to optimize this?
Related
I'm building a script which requires counting the number of occurances of each word in each file, out of about 2000 files, each being around 500KB.
So that is 1GB of data, but MySQL usage goes over 30+ GB (then it runs out and ends).
I've tracked down the cause of this to my liberal use of associative arrays, which looks like this:
for($runc=0; $runc<$numwords; $runc++)
{
$word=trim($content[$runc]);
if ($words[$run][$word]==$wordacceptance && !$wordused[$word])
{
$wordlist[$onword]=$word;
$onword++;
$wordused[$word]=true;
}
$words[$run][$word]++; // +1 to number of occurances of this word in current category
$nwords[$run]++;
}
$run is the current category.
You can see that to count the words's I'm just adding them to the associative array $words[$run][$word]. Which increases with each occurance of each word in each category of files.
Then $wordused[$word] is used to make sure that a word doesn't get added twice to the wordlist.
$wordlist is a simple array (0,1,2,3,etc.) with a list of all different words used.
This eats up gigantic amounts of memory. Is there a more efficient way of doing this? I was considering of using a MySQL memory table, but I want to do the whole thing in PHP so it's fast and portable.
Have you tried the builtin function for counting words?
http://hu2.php.net/manual/en/function.str-word-count.php
EDIT: Or use explode to get an array of words, trim all with array_walk, then sort, and then go though with a for, and count the occurances, and if a new word comes in the list you can flush the number of occurances, so no need for accounting which word was previously.
I want to take a long string (hundreds of thousands of characters) and to compare it against an array of keywords to determine which one of the keywords in the array is mentioned more than the rest.
This seems pretty easy, but I am a bit worried about strstr under performing for this task.
Should I do it in a different way?
Thanks,
I think you can do it in a different way, with a single scan, and if you do it the right way, it can give you a dramatic improvement as of performance.
Create an associative array, where keys are the keywords and values are the occurrences.
Read the string word by word, I mean take a word and put it in a variable. Then, compare it against all the keywords (there are several ways to do it, you can query the associative array with isset). When a keyword is found, increment its counter.
I hope PHP implements associative arrays with some hashmap-like thingie...
Parse the words out in linear fashion. For each word you encounter, increment its count in the associative array of words you are looking for (skipping those you aren't interested in, of course). This will be much faster than strstr.
I need to work out a way to create 10,000 non-repeating random numbers in PHP, and then put it into database table. Number will be 12 digits long.
What is the best way to do this?
At 12 digits long, I don't think the possibility of getting repeats is very large. I would probably just generate the numbers, try to insert them into the table, and if it already exists (assuming you have a unique constraint on that column) just generate another one.
Read e.g. 40000 (=PHP_INT_SIZE * 10000) bytes from /dev/random at once, then split it, modularize it (the % operator), and there you have it.
Then filter it, and repeat the procedure.
That avoids too many syscalls/context switches (between the php runtime, the zend engine, and the operating system itself - I'm not going to dive into details here).
That should be the most performant way of doing it.
Generate 10000 random numbers and place them in an array. Run the array through array_unique. Check the length. If less than 10000, add on a bunch more. Run the array through array_unique. If greater than 10000, then run through array_slice to give 10000. Otherwise, lather, rinse, repeat.
This assumes that you can generate a 12 digit random number without problems (use getrandmax() to see how big you can get....according to php.net on some systems 32k is as large a number as you can get.
$array = array();
while(sizeof($array)<=10000){
$number = mt_rand(0,999999999999);
if(!array_key_exists($number,$array)){
$array[$number] = null;
}
}
foreach($array as $key=>$val){
//write array records to db.
}
You could use either rand() or mt_rand(). mt_rand() is supposed to be faster however.
I want PHP to randomly create a multi-dimensional array by picking a vast amount of items out of predefined lists for n times, but never with 2 times the same.
Let me put that to human words in a real-life example: i want to write a list of vegetables and meat and i want php to make a menu for me, with every day something else then yesterday.
I tried and all i got was the scrambling but there were always doubles :s
Try the shuffle function http://us2.php.net/manual/en/function.shuffle.php
Use either array_rand() or shuffle().
Random != unique
You need to either:
a) create a list containing every possible combination and then randomly select and remove one
or
b) store your results so your random selection can be compared to previous selections.
I am reading excel files through php, the contents are to be displayed in a table on web
I read this data in range A1 to D1 is one data and it is to be presented in this format
The data
is different,
in every,
cell.
This data is to be <br/> line breaked based on strlen (This is a single string is different, in every, cell. Line one The data is heading)
So line breaks are made based on , but max data has to fit in single line
So how can I count strlen to each , so that I can echo if the data can fit in single line or else a line break is made after ,
The data
is different,
in every, cell.
Use strpos() with an offset in a loop in order to find the commas. After finding the first comma, use this position as the new offset for finding the next comma.
Have your tried the PEAR Excel Package(s)? It Simplifies things (reading/writing .xls files)
The str_getcsv() function added in PHP 5.3 may be of use to you.
If not, surely you could just explode(',', $string)?