- 19 Jan, 2013 1 commit
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guiquanz authored
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- 08 Nov, 2012 1 commit
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antirez authored
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- 05 Sep, 2012 1 commit
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Haruto Otake authored
remove unsafe and unnecessary cast. until now, this cast may lead segmentation fault when end > UINT_MAX setbit foo 0 1 bitcount 0 4294967295 => ok bitcount 0 4294967296 => cause segmentation fault. Note by @antirez: the commit was modified a bit to also change the string length type to long, since it's guaranteed to be at max 512 MB in size, so we can work with the same type across all the code path. A regression test was also added.
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- 18 Jul, 2012 1 commit
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antirez authored
For the C standard char can be either signed or unsigned, it's up to the compiler, but Redis assumed that it was signed in a few places. The practical effect of this patch is that now Redis 2.6 will run correctly in every system where char is unsigned, notably the RaspBerry PI and other ARM systems with GCC. Thanks to Georgi Marinov (@eesn on twitter) that reported the problem and allowed me to use his RaspBerry via SSH to trace and fix the issue!
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- 31 May, 2012 1 commit
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antirez authored
In the issue #529 an user reported a bug that can be triggered with the following code: flushdb set a "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" bitop or x a b The bug was introduced with the speed optimization in commit 8bbc0768 that specializes every BITOP operation loop up to the minimum length of the input strings. However the computation of the minimum length contained an error when a non existing key was present in the input, after a key that was non zero length. This commit fixes the bug and adds a regression test for it.
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- 24 May, 2012 7 commits
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antirez authored
This commit adds a fast-path to the BITOP that can be used for all the bytes from 0 to the minimal length of the string, and if there are at max 16 input keys. Often the intersected bitmaps are roughly the same size, so this optimization can provide a 10x speed boost to most real world usages of the command. Bytes are processed four full words at a time, in loops specialized for the specific BITOP sub-command, without the need to check for length issues with the inputs (since we run this algorithm only as far as there is data from all the keys at the same time). The remaining part of the string is intersected in the usual way using the slow but generic algorith. It is possible to do better than this with inputs that are not roughly the same size, sorting the input keys by length, by initializing the result string in a smarter way, and noticing that the final part of the output string composed of only data from the longest string does not need any proecessing since AND, OR and XOR against an empty string does not alter the output (zero in the first case, and the original string in the other two cases). More implementations will be implemented later likely, but this should be enough to release Redis 2.6-RC4 with bitops merged in. Note: this commit also adds better testing for BITOP NOT command, that is currently the faster and hard to optimize further since it just flips the bits of a single input string.
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antirez authored
A bug in the implementation caused BITOP to crash the server if at least one one of the source objects was integer encoded. The new implementation takes an additional array of Redis objects pointers and calls getDecodedObject() to get a reference to a string encoded object, and then uses decrRefCount() to release the object. Tests modified to cover the regression and improve coverage.
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antirez authored
At Redis's default optimization level the command is now much faster, always using a constant-time bit manipualtion technique to count bits instead of GCC builtin popcount, and unrolling the loop. The current implementation performance is 1.5GB/s in a MBA 11" (1.8 Ghz i7) compiled with both GCC and clang. The algorithm used is described here: http://graphics.stanford.edu/~seander/bithacks.html
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antirez authored
bitop.c contains the "Bit related string operations" so it seems more logical to call it bitops instead of bitop. This also makes it matching the name of the test (unit/bitops.tcl).
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antirez authored
We run the array by 32 bit words instead of processing it byte per byte. If the code is compiled using GCC __builtin_popcount() builtin function is used instead.
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antirez authored
The low level popualtion counting function is now separated from the BITCOUNT command implementation, so that the low level function can be further optimized and eventually used in other contexts if needed.
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antirez authored
All the general string operations are implemented in t_string.c, however the bit operations, while targeting the string type, are better served in a specific file where we have the implementations of the following four commands and helper functions: GETBIT SETBIT BITOP BITCOUNT In the future this file will probably contain more code related to making the BITOP and BITCOUNT operations faster.
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