Code optimization: 30% speedup #6
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Code such as case mask_pattern when QRMASKPATTERN[:pattern000] (i + j) % 2 == 0 when QRMASKPATTERN[:pattern001] i % 2 == 0 when QRMASKPATTERN[:pattern010] j % 3 == 0 is very slow because it requires an `Hash#[]` lookup and a `Kernel#===` call for every branch of the `case` construct, 3.5 * 2 function calls on average. We exploit the fact that `mask_pattern` is a Fixnum and pre-populate an array of possible computations. This takes exactly one `Array#[]` lookup and `Proc#call` execution per mask pattern.
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An additional note: the last commit 52c9caf is there so that profilers can understand which part of the code is taking longer to compute. Please keep it as other code builds on top of it. |
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This is awesome work, thankyou! When I get time, I'll pull your changes and double check the tests. All being well I'll merge. Ref your extra commit. Investigation would be good. As you may know this code is a port of a JavaScript encoding lib and I have never seen the real QRCode spec. The only way I have been able to check things is whether the QRCodes read, so I'm not sure how much the error correction is masking problems. |
Code optimization: 30% speedup
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Thanks again for your work. I have merged your initial patch and released a new version of the Gem. If you see any problems, do please let me know. Best, On 13 Aug 2011, at 18:19, gioele wrote:
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Hello,
I refactored a bit of code of RQRCode code in order to make it faster. The refactored code pass all the test in test suite.
I have an additional commit (f4de8484122ecd1271945b159f22ab99e09d53ce) that would bring another 20% speed up, but it fails two test. I'm investigating whether the older test code was wrong or the new refactored code is to blame.
Please pull these changes, there are also some little bug fix inside (for example, the original code did not take level 4 demerit score into account).