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package de.gsi.chart.utils;
import java.math.BigDecimal;
import java.util.WeakHashMap;
import de.gsi.dataset.spi.utils.Tuple;
public final class DigitNumberArithmetic { //NOPMD nomen est omen
static WeakHashMap numberDigitsCache = new WeakHashMap<>();
private DigitNumberArithmetic() {
}
public static Tuple formatStringForSignificantDigits(final double num1, final double num2) {
// TODO: optimise: this function is a performance hotspot (needed for
// axis label calculation)
final int exp1 = (int) Math.log10(Math.abs(num1)) + 1;
final int exp2 = (int) Math.log10(Math.abs(num2)) + 1;
if (Math.signum(num1) != Math.signum(num2) || exp1 != exp2) {
return new Tuple<>((double) Math.max(exp1, exp2), (double) 0);
}
final double inum1 = Math.floor(num1);
final double inum2 = Math.floor(num2);
final double frac1 = num1 - inum1;
final double frac2 = num2 - inum2;
/*
* Even if the numbers are different before the decimal point, numbers after the decimal point may be
* significant: 15.0 - 17.5 - 20.0 - 22.5 - ...
*/
if (inum1 != inum2) {
return new Tuple<>((double) Math.max(exp1, exp2), (double) 0);
}
if (frac1 == 0 && frac2 == 0) {
// System.err.println("both fractions are zero " + num1 + " - " + num2);
return new Tuple<>((double) Math.max(exp1, exp2), (double) 0);
} else {
// System.err.println("fractions are non-zero " + frac1 + " - " + frac2);
}
// check if exponent is the same, if yes, then the export is simple
final String stringNum1 = String.format("%.25f", frac1).replace(".", "");
final String stringNum2 = String.format("%.25f", frac2).replace(".", "");
int count = 1;
for (int i = 1; i < Math.min(stringNum1.length(), stringNum2.length()); i++) {
if (stringNum1.charAt(i) != stringNum2.charAt(i)) {
break;
}
count++;
}
// System.err.println(String.format("number %s vs %s differ in %d-th digit\n", stringNum1, stringNum2, count));
/*
* how many digits do we need? If stepsize is 0.25 for example, we get 025000000 and 050000000. Therefore we
* need two digits after the decimal point (i.e. up to the first digit from the RIGHT, which is different.
*/
// for (int i=Math.min(stringNum1.length(),stringNum2.length())-1;i>0;i--) {
// if (stringNum1.charAt(i) != stringNum2.charAt(i)) {
// count = i;
// break;
// }
// }
// System.err.println(String.format("number %s vs %s differ at least in %d-th digit\n", stringNum1, stringNum2,
// count));
return new Tuple<>((double) Math.max(exp1, exp2), (double) count);
}
public static int getNumberOfSignificantDigits(final double val) {
BigDecimal input = BigDecimal.valueOf(val);
input = input.stripTrailingZeros();
return input.scale() < 0 ? input.precision() - input.scale() : input.precision();
}
public static int getPrecision(final double val) {
BigDecimal input = BigDecimal.valueOf(val);
input = input.stripTrailingZeros();
return input.precision();
}
public static void main(final String[] args) {
final double[] test1 = { 1.23, 1.0, 1.00, 1.23e19, 1.23456789e19, 1.23456789e-19 };
for (final double num : test1) {
final int digits = DigitNumberArithmetic.getNumberOfSignificantDigits(num);
final String msg = String.format("%f %E has %d significant digits", num, num, digits);
System.out.println(msg);
}
System.out.println();
final double[][] test2 = { { 1.23, 1.24 }, { 1000, 1001 }, { 0.001, 0.0011 }, { 5.001, 5.0011 },
{ 10.001, 10.0011 }, { 1, 1.0 + 1e-5 }, { 5.0 / 3.0, 5.0 / 3.0 + 1e-5 },
{ 1.234567e9, 1.234567e9 + 0.001 }, { 1.234567e30, 1.234567e30 + 0.001 } };
for (final double[] pair : test2) {
final int digits = DigitNumberArithmetic.numberDigitsUntilFirstSignificantDigit(pair[0], pair[1]);
final String msg = String.format("%f %f differs in digit %d", pair[0], pair[1], digits);
System.out.println(msg);
}
System.out.println();
final double val1 = 123456789e9;
System.out.println("1: val1=" + String.format("%f", val1));
System.out.println("2: val1=" + String.format("%100.50f", val1));
final double val2 = 123456789 + 1e-8;
System.out.println("1: val2=" + String.format("%f", val2));
System.out.println("2: val2=" + String.format("%100.50f", val2));
System.out.println("3: val1=" + BigDecimal.valueOf(val2).toPlainString());
System.out.println("4: val1=" + BigDecimal.valueOf(val2).stripTrailingZeros());
}
public static int numberDigitsUntilFirstSignificantDigit(final double num1, final double num2) {
// TODO: optimise: this function is a performance hotspot (needed for
// axis label calculation)
final String stringNum1 = numberDigitsCache.computeIfAbsent(num1,
k -> String.format("%.25e", k).replace(".", ""));
final String stringNum2 = numberDigitsCache.computeIfAbsent(num2,
k -> String.format("%.25e", k).replace(".", ""));
// final String stringNum1 = String.format("%.25e", num1).replace(".",
// "");
// final String stringNum2 = String.format("%.25e", num2).replace(".",
// "");
int count = 1;
for (int i = 0; i < Math.min(stringNum1.length(), stringNum2.length()); i++) {
if (stringNum1.charAt(i) != stringNum2.charAt(i)) {
break;
}
count++;
}
return count;
}
public static double roundToFractionalDigits(final double num, final int n) {
final double power = Math.pow(10, n);
return Math.round(num * power) / power;
}
public static double roundToSignificantFigures(final double num, final int n) {
if (num == 0) {
return 0;
}
final double d = Math.ceil(Math.log10(num < 0 ? -num : num));
final int power = n - (int) d;
final double magnitude = Math.pow(10, power);
final long shifted = Math.round(num * magnitude);
return shifted / magnitude;
}
}
