Over the last couple of days, there has been a lot of discussion about a pair of security vulnerabilities nicknamed Spectre and Meltdown. These affect all modern Intel processors, and (in the case of Spectre) many AMD processors and ARM cores. Spectre allows an attacker to bypass software checks to read data from arbitrary locations in the current address space; Meltdown allows an attacker to read
Confirmed: OpenJDK JIT compiler emits efficient conditional move machine codes
Confirmed: OpenJDK JIT compiler emits efficient conditional move machine codes On popular programmers’ Q&A site stackoverflow.com the hit question of the last few years dealt with the effect of branching on program performance. I recommend that you read the brilliant explanation there, but if you don’t have much time, here’s the summary. Modern processors execute commands in a pipeline. While One
In this C++ code, sorting the data (before the timed region) makes the primary loop ~6x faster: #include <algorithm> #include <ctime> #include <iostream> int main() { // Generate data const unsigned arraySize = 32768; int data[arraySize]; for (unsigned c = 0; c < arraySize; ++c) data[c] = std::rand() % 256; // !!! With this, the next loop runs faster. std::sort(data, data + arraySize); // Test clo
Efficient Data Storage for Analytics with Parquet 2.0 - Hadoop Summit 2014 Apache Parquet is an open-source columnar storage format for efficient data storage and analytics. It provides efficient compression and encoding techniques that enable fast scans and queries of large datasets. Parquet 2.0 improves on these efficiencies through techniques like delta encoding, dictionary encoding, run-length
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Did you know that the performance of an if-statement depends on whether its condition has a predictable pattern? If the condition is always true or always false, the branch prediction logic in the processor will pick up the pattern. On the other hand, if the pattern is unpredictable, the if-statement will be much more expensive. In this article, I’ll explain why today’s processors behave this way.
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