Kim Walisch kimwalisch

I enjoy writing highly optimized code.

kimwalisch / wget_list_of_urls

Created January 10, 2014 18:59

Download list of files from terminal using wget

wget --content-disposition -i urls.txt

kimwalisch / find_files_by_keyword

Last active August 29, 2015 13:57

Find all files that contain a user specified keyword (UNix)

	# Find all files KEYWORD
	$ fgrep -R --files-with-matches KEYWORD .

	# Find all files with FILENAME and KEYWORD
	$ find . -name FILENAME -exec fgrep --files-with-matches KEYWORD {} \;

kimwalisch / oracle_sql_commands.sql

Last active August 29, 2015 14:00

oracle_sql_commands

	-- Seach column name in database
	select table_name from all_tab_columns where column_name like '%COLUMN_NAME%';

	-- Seach table name in database
	select table_name from all_tables where table_name like '%TABLE_NAME%';

kimwalisch / get_cache_size.cpp

Last active August 29, 2015 14:08

	// Author: Kim Walisch
	// Released into public domain

	#include <windows.h>
	#include <cstdlib>

	typedef BOOL (WINAPI *LPFN_GLPI)(PSYSTEM_LOGICAL_PROCESSOR_INFORMATION, PDWORD);

	/// Get the CPU's cache size in bytes.
	/// Works on Windows (MSVC, Intel C++ Compiler, Cygwin, ...).

kimwalisch / constexpr_sqrt.cpp

Last active August 29, 2015 14:12

Compile time square root using C++11 constexpr

	///
	/// @file constexpr_sqrt.cpp
	/// @brief Calculate integer square roots at compile time using
	/// C++11 constexpr.
	/// @author Kim Walisch, <[email protected]>
	/// @license Public Domain

	#include <iostream>
	#include <cassert>
	#include <cmath>

kimwalisch / segmented_sieve.cpp

Last active July 31, 2020 08:33

Simple segmented sieve of Eratosthenes implementation

	/// @file segmented_sieve.cpp
	/// @author Kim Walisch, <[email protected]>
	/// @brief This is a simple implementation of the segmented sieve of
	/// Eratosthenes with a few optimizations. It generates the
	/// primes below 10^9 in 0.8 seconds (single-threaded) on an
	/// Intel Core i7-6700 3.4 GHz CPU.
	/// @license Public domain.

	#include <iostream>
	#include <algorithm>

kimwalisch / l1d_cache_size.cpp

Last active November 2, 2022 00:27

Get L1 data cache size on most operating systems

	///
	/// @file l1d_cache_size.cpp
	/// @brief Get the L1 cache size in kilobytes on Windows
	/// and most Unix-like operating systems.
	///
	/// Copyright (C) 2015 Kim Walisch, <[email protected]>
	///
	/// This file is distributed under the BSD License.
	///

kimwalisch / primes.cpp

Last active August 14, 2017 09:01

Generate primes using the primesieve C++ library

	#include <primesieve.hpp>
	#include <iostream>

	int main()
	{
	primesieve::iterator it;
	uint64_t prime = it.next_prime();

	// iterate over the primes below 10^6
	for (; prime < 1000000; prime = it.next_prime())

kimwalisch / sieving_loop.asm

Created November 9, 2015 21:01

primesieve inner sieving loop

	; primesieve inner sieving loop
	; Uses only 11 instructions (x86-64) to cross-off the next 8 multiples
	.L99:
	andb $-3, (%rax)
	andb $-9, (%rax,%r14)
	andb $127, (%rax,%r12)
	andb $-33, (%rax,%rbp)
	andb $-2, (%rax,%r10)
	andb $-65, (%rax,%rbx)
	andb $-5, (%rax,%r9)

kimwalisch / libdivide-without-power-of-2.cpp

Created March 20, 2016 10:19

	struct libdivide_u64_t libdivide_u64_gen(uint64_t d) {
	struct libdivide_u64_t result;

	const uint32_t floor_log_2_d = 63 - libdivide__count_leading_zeros64(d);

	uint64_t proposed_m, rem;
	uint8_t more;
	proposed_m = libdivide_128_div_64_to_64(1ULL << floor_log_2_d, 0, d, &rem); //== (1 << (64 + floor_log_2_d)) / d

	LIBDIVIDE_ASSERT(rem > 0 && rem < d);