Adam Stelmaszczyk AdamStelmaszczyk

AdamStelmaszczyk / Bytecode

Last active August 29, 2015 14:23

Declaring/initializing variables inside or outside of a double (or multiple) loop

	Compiled from "Test.java"
	public class Test {
	public Test();
	Code:
	0: aload_0
	1: invokespecial #1 // Method java/lang/Object."<init>":()V
	4: return

	public void testA();
	Code:

AdamStelmaszczyk / MyBenchmark.java

Created June 25, 2015 21:44

Should I use Java's String.format() if performance is important?

	package org.sample;

	import org.openjdk.jmh.annotations.*;
	import org.openjdk.jmh.runner.Runner;
	import org.openjdk.jmh.runner.RunnerException;
	import org.openjdk.jmh.runner.options.Options;
	import org.openjdk.jmh.runner.options.OptionsBuilder;

	import java.util.concurrent.TimeUnit;

AdamStelmaszczyk / MyBenchmark.java

Last active December 19, 2015 16:20

Most efficient way to make the first character of a String lower case?

	package org.sample;

	import org.openjdk.jmh.annotations.Benchmark;
	import org.openjdk.jmh.infra.Blackhole;

	import java.lang.reflect.Field;

	public class MyBenchmark {

	@Benchmark

AdamStelmaszczyk / MyBenchark.java

Last active August 16, 2021 05:26

Fastest way to check if comma separated string contains at least 1 valid integer?

	package org.sample;

	import org.openjdk.jmh.annotations.*;
	import org.openjdk.jmh.runner.Runner;
	import org.openjdk.jmh.runner.RunnerException;
	import org.openjdk.jmh.runner.options.Options;
	import org.openjdk.jmh.runner.options.OptionsBuilder;

	import java.util.concurrent.TimeUnit;
	import java.util.regex.Pattern;

AdamStelmaszczyk / MyBenchmark.java

Last active December 19, 2015 16:11

Is returning a static empty array faster than creating a new one?

	package org.sample;

	import org.openjdk.jmh.annotations.Benchmark;
	import org.openjdk.jmh.annotations.Fork;
	import org.openjdk.jmh.infra.Blackhole;

	public class MyBenchmark {

	private static final String[] EMPTY_STRING_ARRAY = new String[0];

AdamStelmaszczyk / 10.prof

Last active June 8, 2017 16:42

How to optimize this Haskell code summing up the primes?

	Thu Jun 8 18:42 2017 Time and Allocation Profiling Report (Final)

	10 +RTS -p -RTS

	total time = 7.79 secs (7786 ticks @ 1000 us, 1 processor)
	total alloc = 6,259,859,408 bytes (excludes profiling overheads)

	COST CENTRE MODULE %time %alloc

	p.sieve.update.decrease Main 52.2 67.5

AdamStelmaszczyk / 10.hs

Last active June 8, 2017 18:23

IntMap instead Map, Int instead Integer

	import Data.List

	import Data.IntMap (IntMap, (!))
	import qualified Data.IntMap as IntMap

	p :: Int -> Int
	p n = (sieve (IntMap.fromList [(i, i * (i + 1) `div` 2 - 1) \| i <- vs]) 2 r vs) ! n
	where vs = [n `div` i \| i <- [1..r]] ++ reverse [1..n `div` r - 1]
	r = floor (sqrt (fromIntegral n))

AdamStelmaszczyk / 10_v2.hs

Created June 9, 2017 12:42

After Shersh code review

	import Data.List
	import Data.IntMap.Strict(IntMap, (!))
	import qualified Data.IntMap.Strict as IntMap

	problem10 :: Int -> Int
	problem10 n = (sieve (IntMap.fromList [(i, i * (i + 1) `div` 2 - 1) \| i <- vs]) 2 r vs) ! n
	where vs = [n `div` i \| i <- [1..r]] ++ [n', n' - 1 .. 1]
	r = floor (sqrt (fromIntegral n))
	n' = n `div` r - 1

AdamStelmaszczyk / slow.hs

Last active June 13, 2017 20:23

hashtables

	import Data.List
	import qualified Data.HashTable.IO as H
	import Data.Maybe (fromJust)

	type HashTable k v = H.BasicHashTable k v

	(!) :: IO (HashTable Int Int) -> Int -> IO Int
	(!) m k = do
	h <- m
	x <- H.lookup h k

AdamStelmaszczyk / 10.cpp

Last active June 19, 2017 10:36

C++