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    <p>At least if I'm reading this correctly, I think I'd take a rather more C-like approach. Instead of reading a line, then breaking it up into tokens, and stripping out the characters you don't want, I'd read a character at a time, and based on the character I read, decide whether to add it to the current token, end the token and add it to the current line, or end the line and add it to the vector of lines:</p> <pre><code>#include &lt;vector&gt; #include &lt;string&gt; #include &lt;stdio.h&gt; #include &lt;time.h&gt; std::vector&lt;std::vector&lt;std::string&gt; &gt; read_tokens(char const *filename) { std::vector&lt;std::vector&lt;std::string&gt; &gt; lines; FILE *infile= fopen(filename, "r"); int ch; std::vector&lt;std::string&gt; line; std::string token; while (EOF != (ch = getc(infile))) { switch(ch) { case '\n': lines.push_back(line); line.clear(); token.clear(); break; case '"': break; case '*': line.push_back(token); token.clear(); break; default: token.push_back(ch); } } return lines; } int main() { clock_t start = clock(); std::vector&lt;std::vector&lt;std::string&gt; &gt; lines = read_tokens("sample_tokens.txt"); clock_t finish = clock(); printf("%f seconds\n", double(finish-start)/CLOCKS_PER_SEC); return 0; } </code></pre> <p>Doing a quick test with this on a file with a little over 200K copies of the sample you gave in the comment, it's reading and (apparently) tokenizing the data in ~3.5 second with gcc or ~4.5 seconds with VC++. I'd be a little surprised to see anything get a whole lot faster (at least without faster hardware).</p> <p>As an aside, this is handling memory about as you originally did, which (at least in my opinion) is pretty strong evidence that managing memory in the vector probably isn't a major bottleneck.</p>
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    1. POC++ - Why is reading lines from a file by tokenizer is so slow?
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    1. CO@JerryCoffin Paddy also mentioned reading the entire file into the memory first. How would that effect the speed? Does that have a huge difference?
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    2. CO@pod That wouldn't be much use if you're turning it into strings anyway. I was talking about reading the whole lot, tokenizing it in-place, and indexing into it (so your strings would be char*). I'd only do that if I was really concerned about speed.
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    3. CO@pod And will that data file fit in RAM? How big is it? Do you need to store the whole thing in memory at once?
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