• Faster algorithm for max(ctz(x), ctz(y))?

    13 For min(ctz(x), ctz(y)), we can use ctz(x | y) to gain better performance. But what about max(ctz(x), ctz(y))? ctz represents "count trailing zeros". C++ Version (Compiler Explorer) #include <algorithm> #include <bit> #include <cstdint> int32_t test2(uint64_t x, uint64_t y) { return std::max(std::countr_zero(x), std::countr_zero(y)); } Rust Version (Compiler Explorer) pub fn test2(x: u64, y: u64) -> […]

  • Efficiently match all values of a vector in another vector

    11 I’m looking to find an efficient method of matching all values of vector x in vector y rather than just the first position, as is returned by match(). What I’m after essentially is the default behavior of pmatch() but without partial matching: x <- c(3L, 1L, 2L, 3L, 3L, 2L) y <- c(3L, 3L, […]

  • Repeat rows in DataFrame with respect to column

    7 I have a Pandas DataFrame that looks like this: df = pd.DataFrame({‘col1’: [1, 2, 3], ‘col2’: [4, 5, 6], ‘col3’: [7, 8, 9]}) df col1 col2 col3 0 1 4 7 1 2 5 8 2 3 6 9 I would like to create a Pandas DataFrame like this: df_new col1 col2 col3 0 […]