Awesome
FastDoubleParser
This is a Java port of Daniel Lemire's fast_float project.
This project provides parsers for double, float, BigDecimal and BigInteger values.
The double and float parsers are optimised for speed for the most common inputs.
The BigDecimal and BigInteger parsers are optimised for speed on all inputs.
The code in this project contains optimised versions for Java SE 1.8, 11, 17, 21 and 22. The code is released in a single multi-release jar, which contains the code for all these versions except 20.
License
Project License
This project can be licensed under the MIT License.
Code License
Some code in this project is derived from the following projects:
- fast_float, licensed under MIT License
- bigint, licensed under BSD 2-clause License
The code is marked as such.
If you redistribute code, you must follow the terms of all involved licenses (MIT License, BSD 2-clause License).
The build scripts in this project do include the license files into the jar files. So that the released jar files automatically comply with the licenses, when you use them.
Dependency
You can download released Jar files from github, or from a public Maven using the following dependency descriptor:
<dependency>
<groupId>ch.randelshofer</groupId>
<artifactId>fastdoubleparser</artifactId>
<version>…version…</version>
</dependency>
Usage
module MyModule {
requires ch.randelshofer.fastdoubleparser;
}
import ch.randelshofer.fastdoubleparser.JavaDoubleParser;
import ch.randelshofer.fastdoubleparser.JavaFloatParser;
import ch.randelshofer.fastdoubleparser.JavaBigDecimalParser;
import ch.randelshofer.fastdoubleparser.JavaBigIntegerParser;
import ch.randelshofer.fastdoubleparser.JsonDoubleParser;
import ch.randelshofer.fastdoubleparser.NumberFormatSymbols;
import ch.randelshofer.fastdoubleparser.ConfigurableDoubleParser;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.text.DecimalFormatSymbols;
import java.util.List;
import java.util.Locale;
import java.util.Set;
class MyMain {
public static void main(String... args) {
double d = JavaDoubleParser.parseDouble("1.2345e135");
System.out.println("Java double value: " + d);
float f = JavaFloatParser.parseFloat("1.2345f");
System.out.println("Java float value: " + f);
BigDecimal bd = JavaBigDecimalParser.parseBigDecimal("1.2345");
System.out.println("Java big decimal value: " + bd);
BigInteger bi = JavaBigIntegerParser.parseBigInteger("12345");
System.out.println("Java big integer value: " + bi);
double jsonD = JsonDoubleParser.parseDouble("1.2345e85");
System.out.println("JSON double value: " + jsonD);
var symbols = NumberFormatSymbols.fromDecimalFormatSymbols(new DecimalFormatSymbols(Locale.GERMAN));
boolean ignoreCase = true;
var confdParser = new ConfigurableDoubleParser(symbols, ignoreCase);
double confD1 = confdParser.parseDouble("123.456,89e5");
double confD2 = confdParser.parseDouble("-0.15425,89E-5");
System.out.println("Double value in German Locale: " + confD1);
System.out.println("Another double value in German Locale: " + confD2);
symbols = NumberFormatSymbols.fromDecimalFormatSymbols(new DecimalFormatSymbols(Locale.forLanguageTag("zh-CN")));
symbols = symbols
.withDigits(List.of('〇', '一', '二', '三', '四', '五', '六', '七', '八', '九'))
.withExponentSeparator((Set.of("*一〇^")));
confdParser = new ConfigurableDoubleParser(symbols, ignoreCase);
double confZh = confdParser.parseDouble("四一.五七五三七一六六二一四五九八*一〇^七");
System.out.println("Double value in Chinese Locale: " + confZh);
}
}
The parse...()-methods take a CharacterSequence. a char-array or a byte-array as argument. This way, you can
parse from a StringBuffer or an array without having to convert your input to a String. Parsing from an array is
faster, because the parser can process multiple characters at once using SIMD instructions.
Performance Tuning
The JVM does not reliably inline String.charAt(int). This may negatively impact the
parse...()-methods that take a CharacterSequence as an argument.
To ensure optimal performance, you can use the following java command line option:
-XX:CompileCommand=inline,java/lang/String.charAt
Performance Characteristics
float and double parsers
On common input data, the fast double and float parsers are about 4 times faster than
java.lang.Double.valueOf(String) and java.lang.Float.valueOf(String).
For less common inputs, the fast parsers can be slower than their java.lang counterparts.
A double value can always be specified exactly with up to 17 digits in the significand.
A float only needs up to 8 digits.
Therefore, inputs with more than 19 digits in the significand are considered less common.
Such inputs are expected to occur if the input data was created with more precision, and needs to be narrowed down
to the precision of a double or a float.
BigDecimal and BigInteger parsers
On common input data, the fast BigDecimal and BigInteger parsers are slightly faster than
java.math.BigDecimal(String) and java.math.BigInteger(String).
For less common inputs with many digits, the fast parsers can be a lot faster than their java.math counterparts.
The fast parsers can convert even the longest supported inputs in less than 6 minutes, whereas
their java.math counterparts need months!
The fast parsers convert digit characters from base 10 to a bit sequence in base 2
using a divide-and-conquer algorithm. Small sequences of digits are converted
individually to bit sequences and then gradually combined to the final bit sequence.
This algorithm needs to perform multiplications of very long bit sequences.
The multiplications are performed in the frequency domain using a discrete fourier transform.
The multiplications in the frequency domain can be performed in O(N log N (log log N)) time,
where N is the number of digits.
In contrast, conventional multiplication algorithms in the time domain need O(N²) time.
Memory usage and computation time
The memory usage depends on the result type and the maximal supported input character length.
The computation times are given for a Mac mini 2018 with Intel(R) Core(TM) i7-8700B CPU @ 3.20GHz.
| Parser | Result Type | Maximal<br/>input length | Memory usage<br/>JVM -Xmx | Computation<br/>Time |
|---|---|---|---|---|
| JavaDoubleParser | java.lang.Double | 2^31 - 5 | 10 gigabytes | < 5 sec |
| JavaFloatParser | java.lang.Float | 2^31 - 5 | 10 gigabytes | < 5 sec |
| JavaBigIntegerParser | java.math.BigInteger | 1,292,782,622 | 16 gigabytes | < 6 min |
| JavaBigDecimalParser | java.math.BigDecimal | 1,292,782,635 | 16 gigabytes | < 6 min |
Performance measurements
The data file canada.txt
This file contains numbers in the range from -128 to +128.
Most input lines look like this: 52.038048000000117.
CPU: Apple M2 Max<br> OS: Mac OS X, 14.7, 12 processors available<br> VM: Java 23, OpenJDK 64-Bit Server VM, Azul Systems, Inc., 23.0.1+11<br> -XX:CompileCommand=inline,java/lang/String.charAt
| Method | MB/s | stdev | Mfloats/s | ns/f | speedup | JDK |
|---|---|---|---|---|---|---|
| java.lang.Double | 107.96 | 2.0 % | 6.20 | 161.19 | 1.00=a | 23.0.1 |
| java.lang.Float | 118.12 | 3.1 % | 6.79 | 147.32 | 1.00=b | 23.0.1 |
| java.math.BigDecimal | 400.25 | 4.8 % | 23.00 | 43.48 | 1.00=c | 23.0.1 |
| java.text.NumberFormat | 72.06 | 1.6 % | 4.14 | 241.49 | 1.00=d | 23.0.1 |
| com.ibm.icu.text.NumberFormat | 24.32 | 2.7 % | 1.40 | 715.62 | 1.00=e | 23.0.1 |
| JavaDoubleParser CharSequence | 532.05 | 4.3 % | 30.58 | 32.71 | 4.93*a | 23.0.1 |
| JavaDoubleParser char[] | 973.38 | 7.1 % | 55.94 | 17.88 | 9.02*a | 23.0.1 |
| JavaDoubleParser byte[] | 962.18 | 8.0 % | 55.29 | 18.09 | 8.91*a | 23.0.1 |
| JsonDoubleParser CharSequence | 575.45 | 5.8 % | 33.07 | 30.24 | 5.33*a | 23.0.1 |
| JsonDoubleParser char[] | 991.20 | 6.2 % | 56.96 | 17.56 | 9.18*a | 23.0.1 |
| JsonDoubleParser byte[] | 990.74 | 5.5 % | 56.93 | 17.56 | 9.18*a | 23.0.1 |
| JavaFloatParser CharSequence | 572.02 | 6.0 % | 32.87 | 30.42 | 4.84*b | 23.0.1 |
| JavaFloatParser char[] | 1007.96 | 21.5 % | 57.92 | 17.26 | 8.53*b | 23.0.1 |
| JavaFloatParser byte[] | 1011.75 | 6.3 % | 58.14 | 17.20 | 8.57*b | 23.0.1 |
| JavaBigDecimalParser CharSequence | 773.44 | 5.9 % | 44.45 | 22.50 | 1.93*c | 23.0.1 |
| JavaBigDecimalParser char[] | 1140.28 | 6.3 % | 65.53 | 15.26 | 2.85*c | 23.0.1 |
| JavaBigDecimalParser byte[] | 1097.82 | 15.1 % | 63.09 | 15.85 | 2.74*c | 23.0.1 |
| ConfigurableDoubleParser CharSequence | 483.99 | 5.6 % | 27.81 | 35.95 | 6.72*d | 23.0.1 |
| ConfigurableDoubleParser char[] | 689.58 | 7.1 % | 39.63 | 25.23 | 9.57*d | 23.0.1 |
| ConfigurableDoubleParser byte[] | 625.56 | 4.4 % | 35.95 | 27.82 | 8.68*d | 23.0.1 |
| ConfigurableDoubleParserCI CharSequence | 493.74 | 5.4 % | 28.37 | 35.24 | 6.85*d | 23.0.1 |
| ConfigurableDoubleParserCI char[] | 701.50 | 4.6 % | 40.31 | 24.81 | 9.73*d | 23.0.1 |
| ConfigurableDoubleParserCI byte[] | 531.04 | 6.5 % | 30.52 | 32.77 | 7.37*d | 23.0.1 |
Mac Mini (2018)<br> CPU: Intel(R) Core(TM) i7-8700B CPU @ 3.20GHz<br> OS: Mac OS X, 15.0.1, 12 processors available<br> VM: Java 24, OpenJDK 64-Bit Server VM, Oracle Corporation, 24-ea+20-2362<br>
| Method | MB/s | stdev | Mfloats/s | ns/f | speedup | JDK |
|---|---|---|---|---|---|---|
| java.lang.Double | 88.84 | 3.8 % | 5.11 | 195.87 | 1.00=a | 24-ea |
| java.lang.Float | 101.30 | 3.7 % | 5.82 | 171.78 | 1.00=b | 24-ea |
| java.math.BigDecimal | 321.36 | 8.6 % | 18.47 | 54.15 | 1.00=c | 24-ea |
| java.text.NumberFormat | 45.79 | 3.0 % | 2.63 | 379.99 | 1.00=d | 24-ea |
| com.ibm.icu.text.NumberFormat | 15.98 | 3.0 % | 0.92 | 1088.62 | 1.00=e | 24-ea |
| JavaDoubleParser CharSequence | 393.16 | 9.2 % | 22.59 | 44.26 | 4.43*a | 24-ea |
| JavaDoubleParser char[] | 595.25 | 12.8 % | 34.21 | 29.23 | 6.70*a | 24-ea |
| JavaDoubleParser byte[] | 685.38 | 10.1 % | 39.39 | 25.39 | 7.71*a | 24-ea |
| JsonDoubleParser CharSequence | 391.58 | 9.8 % | 22.50 | 44.44 | 4.41*a | 24-ea |
| JsonDoubleParser char[] | 609.59 | 10.4 % | 35.03 | 28.55 | 6.86*a | 24-ea |
| JsonDoubleParser byte[] | 675.52 | 9.2 % | 38.82 | 25.76 | 7.60*a | 24-ea |
| JavaFloatParser CharSequence | 402.35 | 9.1 % | 23.12 | 43.25 | 3.97*b | 24-ea |
| JavaFloatParser char[] | 712.35 | 10.5 % | 40.94 | 24.43 | 7.03*b | 24-ea |
| JavaFloatParser byte[] | 626.70 | 9.4 % | 36.01 | 27.77 | 6.19*b | 24-ea |
| JavaBigDecimalParser CharSequence | 428.92 | 17.7 % | 24.65 | 40.57 | 1.33*c | 24-ea |
| JavaBigDecimalParser char[] | 660.18 | 12.2 % | 37.94 | 26.36 | 2.05*c | 24-ea |
| JavaBigDecimalParser byte[] | 669.97 | 11.5 % | 38.50 | 25.97 | 2.08*c | 24-ea |
| ConfigurableDoubleParser CharSequence | 335.02 | 9.2 % | 19.25 | 51.94 | 7.32*d | 24-ea |
| ConfigurableDoubleParser char[] | 527.14 | 12.1 % | 30.29 | 33.01 | 11.51*d | 24-ea |
| ConfigurableDoubleParser byte[] | 474.35 | 7.6 % | 27.26 | 36.69 | 10.36*d | 24-ea |
| ConfigurableDoubleParserCI CharSequence | 330.35 | 9.9 % | 18.98 | 52.67 | 7.21*d | 24-ea |
| ConfigurableDoubleParserCI char[] | 519.32 | 9.8 % | 29.84 | 33.51 | 11.34*d | 24-ea |
| ConfigurableDoubleParserCI byte[] | 406.10 | 7.4 % | 23.34 | 42.85 | 8.87*d | 24-ea |
Comparison with C version
For comparison. here are the test results
of simple_fastfloat_benchmark
on the same computer:
version: Thu Mar 31 10:18:12 2022 -0400 f2082bf747eabc0873f2fdceb05f9451931b96dc
Intel(R) Core(TM) i7-8700B CPU @ 3.20GHz SIMD-256
$ ./build/benchmarks/benchmark
# parsing random numbers
available models (-m): uniform one_over_rand32 simple_uniform32 simple_int32 int_e_int simple_int64 bigint_int_dot_int big_ints
model: generate random numbers uniformly in the interval [0.0.1.0]
volume: 100000 floats
volume = 2.09808 MB
netlib : 317.31 MB/s (+/- 6.0 %) 15.12 Mfloat/s 66.12 ns/f
doubleconversion : 263.89 MB/s (+/- 4.2 %) 12.58 Mfloat/s 79.51 ns/f
strtod : 86.13 MB/s (+/- 3.7 %) 4.10 Mfloat/s 243.61 ns/f
abseil : 467.27 MB/s (+/- 9.0 %) 22.27 Mfloat/s 44.90 ns/f
fastfloat : 880.79 MB/s (+/- 6.6 %) 41.98 Mfloat/s 23.82 ns/f
Java 22, OpenJDK 64-Bit Server VM, Oracle Corporation, 22.0.1+8-16
java.lang.Double : 94.32 MB/s (+/- 3.1 %) 5.41 Mfloat/s 184.73 ns/f 1.00 speedup
JavaDoubleParser CharSequence: 585.84 MB/s (+/-12.4 %) 33.62 Mfloat/s 29.74 ns/f 6.21 speedup
JavaDoubleParser char[] : 659.27 MB/s (+/- 9.6 %) 37.84 Mfloat/s 26.43 ns/f 6.99 speedup
JavaDoubleParser byte[] : 729.46 MB/s (+/- 9.7 %) 41.86 Mfloat/s 23.89 ns/f 7.73 speedup
'
$ ./build/benchmarks/benchmark -f data/canada.txt
# read 111126 lines
volume = 1.93374 MB
netlib : 337.79 MB/s (+/- 5.8 %) 19.41 Mfloat/s 51.52 ns/f
doubleconversion : 254.22 MB/s (+/- 6.0 %) 14.61 Mfloat/s 68.45 ns/f
strtod : 73.33 MB/s (+/- 7.1 %) 4.21 Mfloat/s 237.31 ns/f
abseil : 411.11 MB/s (+/- 7.3 %) 23.63 Mfloat/s 42.33 ns/f
fastfloat : 741.32 MB/s (+/- 5.3 %) 42.60 Mfloat/s 23.47 ns/f
Java 22, OpenJDK 64-Bit Server VM, Oracle Corporation, 22.0.1+8-16
java.lang.Double : 87.48 MB/s (+/- 3.2 %) 5.03 Mfloat/s 198.93 ns/f 1.00 speedup
JavaDoubleParser CharSequence: 386.93 MB/s (+/- 8.8 %) 22.24 Mfloat/s 44.97 ns/f 4.42 speedup
JavaDoubleParser char[] : 637.55 MB/s (+/- 9.0 %) 36.64 Mfloat/s 27.29 ns/f 7.29 speedup
JavaDoubleParser byte[] : 694.16 MB/s (+/- 7.9 %) 39.89 Mfloat/s 25.07 ns/f 7.94 speedup
Building and running the code
This project requires at least the items below to build it from source:
- Maven 3.9.9
- OpenJDK SE 23
This project contains optimised code for various JDK versions. If you intend to assess the fitness and/or performance of this project for all supported JDKs, you also need to install the following items:
- OpenJDK SE 8
- OpenJDK SE 11
- OpenJDK SE 17
- OpenJDK SE 21
- OpenJDK SE 23
When you clone the code repository from github. you can choose from the following branches:
mainAims to contain only working code.devThis code may or may not work. This code uses the experimental Vector API, and the Foreign Memory Access API, that are included in Java 23.
Command sequence with Java SE 23 on macOS:
git clone https://github.com/wrandelshofer/FastDoubleParser.git
cd FastDoubleParser
export JAVA_HOME=/Library/Java/JavaVirtualMachines/zulu-23.jdk/Contents/Home
javac --enable-preview -source 23 -d out -encoding utf8 --module-source-path fastdoubleparser-dev/src/main/java --module ch.randelshofer.fastdoubleparser
javac --enable-preview -source 23 -d out -encoding utf8 -p out --module-source-path fastdoubleparserdemo-dev/src/main/java --module ch.randelshofer.fastdoubleparserdemo
java -XX:CompileCommand=inline,java/lang/String.charAt --enable-preview -p out -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown
java -XX:CompileCommand=inline,java/lang/String.charAt --enable-preview -p out -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada.txt
java -XX:CompileCommand=inline,java/lang/String.charAt --enable-preview -p out -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/mesh.txt
java -XX:CompileCommand=inline,java/lang/String.charAt --enable-preview -p out -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada_hex.txt
Command sequence with Azul Zulu Java SE 8, 11, 17, 21, and 23, and Maven 3.9.8 on macOS:
git clone https://github.com/wrandelshofer/FastDoubleParser.git
cd FastDoubleParser
export JAVA_HOME=/Library/Java/JavaVirtualMachines/zulu-23.jdk/Contents/Home
mvn clean
mvn package
export JAVA_HOME=/Library/Java/JavaVirtualMachines/zulu-23.jdk/Contents/Home
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada.txt
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/mesh.txt
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada_hex.txt
export JAVA_HOME=/Library/Java/JavaVirtualMachines/zulu-21.jdk/Contents/Home
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada.txt
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/mesh.txt
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada_hex.txt
export JAVA_HOME=/Library/Java/JavaVirtualMachines/zulu-17.jdk/Contents/Home
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada.txt
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/mesh.txt
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada_hex.txt
export JAVA_HOME=/Library/Java/JavaVirtualMachines/zulu-11.jdk/Contents/Home
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada.txt
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/mesh.txt
java -XX:CompileCommand=inline,java/lang/String.charAt -p fastdoubleparser/target:fastdoubleparserdemo/target -m ch.randelshofer.fastdoubleparserdemo/ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada_hex.txt
export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk-8.jdk/Contents/Home
java -XX:CompileCommand=inline,java/lang/String.charAt -cp "fastdoubleparser/target/*:fastdoubleparserdemo/target/*" ch.randelshofer.fastdoubleparserdemo.Main --markdown
java -XX:CompileCommand=inline,java/lang/String.charAt -cp "fastdoubleparser/target/*:fastdoubleparserdemo/target/*" ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada.txt
java -XX:CompileCommand=inline,java/lang/String.charAt -cp "fastdoubleparser/target/*:fastdoubleparserdemo/target/*" ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/mesh.txt
java -XX:CompileCommand=inline,java/lang/String.charAt -cp "fastdoubleparser/target/*:fastdoubleparserdemo/target/*" ch.randelshofer.fastdoubleparserdemo.Main --markdown FastDoubleParserDemo/data/canada_hex.txt
IntelliJ IDEA with Java SE 8, 11, 17, 21, 23 on macOS
Prerequisites:
- Install the following Java SDKs: 8, 11, 17, 21, 23. If you do not need to edit the code, you only need to install the Java 23 SDK.
- Install IntelliJ IDEA
Steps:
-
Start IntelliJ IDEA
-
From the main menu, choose Git > Clone...
-
In the dialog that opens, enter the URL https://github.com/wrandelshofer/FastDoubleParser.git, specify the directory in which you want to save the project and click Clone.
-
Intellij IDEA will now clone the repository and open a new project window. However, the project modules are not yet configured correctly.
-
From the main menu of the new project window, choose View > Tool Windows > Maven
-
In the Maven tool window, run the Maven build Parent project for FastDoubleParser > Lifecycle > compile
-
In the toolbar of the Maven tool window, click Reload All Maven Projects
-
Intellij IDEA knows now for each module, where the source, generated source, test source, and generated test source folders are. However, the project modules have still incorrect JDK dependencies.
-
You can skip this step, if you do not want to edit the code. From the main menu, choose File > Project Structure...
-
You can skip this step, if you do not want to edit the code. In the dialog that opens, select in the navigation bar Project Settings > Modules
-
You can skip this step, if you do not want to edit the code. For each module in the right pane of the dialog, select the Dependencies tab. Specify the corresponding Module SDK for modules which have a name that ends in -Java8, -Java11, -Java17, -Java21. Do not change modules with other name endings - they must stay on the Java 20 SDK.
-
From the main menu, choose Build > Build Project Intellij IDEA will now properly build the project.
Editing the code
The majority of the code is located in the module named fastdoubleparser-dev, and fastdoubleparserdemo-dev. The code in these modules uses early access features of the Java 20 SDK.
Modules which have a name that ends in -Java8, -Java11, -Java17, -Java21, -Java23 contain deltas of the -dev modules.
The delta code is located in the source and test folders of the module. Code from the -dev module is located in the generated source and generated test source folders.
The Maven POM of a module contains maven-resources-plugin elements that copy code from the -dev module to the delta modules.
Testing the code
Unfortunately it is not possible to test floating parsers exhaustively, because the input and output spaces are far too big.
| Parser | Input Space | Output Space |
|---|---|---|
| JavaDoubleParser | 1 to 2<sup>31</sup>-1 chars<br>= 65536<sup>2<sup>31</sup></sup><br>= 2<sup>34,359,738,368</sup> | 64 bits<br>= 2<sup>64</sup> |
| JavaFloatParser | 1 to 2<sup>31</sup>-1 chars<br>= 2<sup>34,359,738,368</sup> | 32 bits<br>= 2<sup>32</sup> |
| JsonDoubleParser | 1 to 2<sup>31</sup>-1 chars<br>= 2<sup>34,359,738,368</sup> | 64 bits<br>= 2<sup>64</sup> |
| JavaBigIntegerParser | 1 to 1,292,782,622 chars<br>= 65536<sup>1292782623</sup><br>= 2<sup>20,684,521,968</sup> | 0 to 2<sup>31</sup> bits<br>= 2<sup>2<sup>31</sup></sup><br>= 2<sup>2,147,483,648</sup> |
| JavaBigDecimalParser | 1 to 1,292,782,635 chars<br>= 65536<sup>1292782636</sup><br>= 2<sup>20,684,522,176</sup> | 0 to 2<sup>31</sup> bit mantissa * 64 bit exponent<br>= 2<sup>12,884,901,888</sup> |
You can quickly run a number of hand-picked tests that aim for 100 % line coverage:
mvn -DenableLongRunningTests=true test
You can run additional tests with the following command. The purpose of these tests is to explore additional regions of the input and output spaces.
mvn -DenableLongRunningTests=true test