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329: Retain floating point precision when converting floats #331

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329: Retain floating point precision when converting floats #331

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903a961
Add tests
daniel-shuy Feb 16, 2021
a05c13b
329: Retain floating point precision when converting floats
daniel-shuy Feb 16, 2021
faa269f
Use Number#doubleValue()/floatValue() instead of cast
daniel-shuy Feb 16, 2021
c0a5e9a
Remove unnecessary instanceof Double check
daniel-shuy Feb 16, 2021
d05aff2
Simplify Double + Float multiplication
daniel-shuy Feb 17, 2021
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46 changes: 26 additions & 20 deletions src/main/java/tech/units/indriya/function/DefaultNumberSystem.java
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Original file line number Diff line number Diff line change
Expand Up @@ -247,10 +247,10 @@ public Number reciprocal(Number number) {
return ((RationalNumber) number).reciprocal();
}
if(number instanceof Double) {
return RationalNumber.of((double)number).reciprocal();
return RationalNumber.of(number.doubleValue()).reciprocal();
}
if(number instanceof Float) {
return RationalNumber.of(number.doubleValue()).reciprocal();
return RationalNumber.of(number.floatValue()).reciprocal();
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I'd rather not introduce a RationalNumber.of(float) for the reasons discussed in (#332).

}
throw unsupportedNumberType(number);
}
Expand Down Expand Up @@ -615,7 +615,7 @@ private BigDecimal toBigDecimal(Number number) {
return BigDecimal.valueOf(number.longValue());
}
if(number instanceof Double || number instanceof Float) {
return BigDecimal.valueOf(number.doubleValue());
return new BigDecimal(number.toString());
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I'd rather not convert floats to String and then to BigDecimal if the general scheme (as up for discussion in #332) is to first properly extend floats to double before converting to BigDecimal. If we agree on this scheme we should be consistent with it throughout the entire implementation.

}
if(number instanceof RationalNumber) {
throw unexpectedCodeReach();
Expand Down Expand Up @@ -668,7 +668,7 @@ private Number addWideAndNarrow(
}

if(narrow instanceof Double || narrow instanceof Float) {
return ((BigDecimal) wide).add(BigDecimal.valueOf(narrow.doubleValue()), Calculus.MATH_CONTEXT);
return ((BigDecimal) wide).add(new BigDecimal(narrow.toString()), Calculus.MATH_CONTEXT);
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dito: consistency

}

if(narrow instanceof RationalNumber) {
Expand All @@ -685,23 +685,23 @@ private Number addWideAndNarrow(

if(narrow instanceof Double || narrow instanceof Float) {
//converting to BigDecimal, because especially fractional addition is sensitive to precision loss
return BigDecimal.valueOf(wide.doubleValue())
.add(BigDecimal.valueOf(narrow.doubleValue()));
return new BigDecimal(wide.toString())
.add(new BigDecimal(narrow.toString()));
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dito: consistency

}

if(narrow instanceof RationalNumber) {
//TODO[220] can we do better than that, eg. by converting BigDecimal to RationalNumber
return BigDecimal.valueOf(wide.doubleValue())
return new BigDecimal(wide.toString())
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At this point wide is potentially a float, so don't break consistency.

.add(((RationalNumber) narrow).bigDecimalValue());
}

if(narrow instanceof BigInteger) {
return BigDecimal.valueOf(wide.doubleValue())
return new BigDecimal(wide.toString())
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dito: consistency

.add(new BigDecimal((BigInteger) narrow));
}

// at this point we know, that 'narrow' is one of {(Atomic)Long, (Atomic)Integer, Short, Byte}
return BigDecimal.valueOf(wide.doubleValue())
return new BigDecimal(wide.toString())
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At this point wide is potentially a float, so don't break consistency.

.add(BigDecimal.valueOf(narrow.longValue()));

}
Expand Down Expand Up @@ -748,7 +748,7 @@ private Number multiplyWideAndNarrow(
}

if(narrow instanceof Double || narrow instanceof Float) {
return ((BigDecimal) wide).multiply(BigDecimal.valueOf(narrow.doubleValue()), Calculus.MATH_CONTEXT);
return ((BigDecimal) wide).multiply(new BigDecimal(narrow.toString()), Calculus.MATH_CONTEXT);
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dito: consistency

}

if(narrow instanceof RationalNumber) {
Expand All @@ -765,23 +765,28 @@ private Number multiplyWideAndNarrow(

if(narrow instanceof Double || narrow instanceof Float) {
// not converting to BigDecimal, because fractional multiplication is not sensitive to precision loss
return wide.doubleValue() * narrow.doubleValue();
if (wide instanceof Float && narrow instanceof Float) {
// return float if both are floats
return wide.floatValue() * narrow.floatValue();
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I'd rather not do that, as by extension to double we can guarantee the float value multiplication not to overflow. Its a corner case granted, but why risk that?

} else {
return wide.doubleValue() * narrow.doubleValue();
}
}

if(narrow instanceof RationalNumber) {
//TODO[220] can we do better than that, eg. by converting BigDecimal to RationalNumber
return BigDecimal.valueOf(wide.doubleValue())
return new BigDecimal(wide.toString())
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At this point wide is potentially a float, so don't break consistency.

.multiply(((RationalNumber) narrow).bigDecimalValue());
}

if(narrow instanceof BigInteger) {
return BigDecimal.valueOf(wide.doubleValue())
return new BigDecimal(wide.toString())
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dito: consistency

.multiply(new BigDecimal((BigInteger) narrow));
}

// at this point we know, that 'narrow' is one of {(Atomic)Long, (Atomic)Integer, Short, Byte}
return BigDecimal.valueOf(wide.doubleValue())
.multiply(BigDecimal.valueOf(narrow.longValue()));
return new BigDecimal(wide.toString())
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At this point wide is potentially a float, so don't break consistency.

.multiply(BigDecimal.valueOf(narrow.longValue()));

}

Expand Down Expand Up @@ -821,7 +826,7 @@ private int compareWideVsNarrow(
}

if(narrow instanceof Double || narrow instanceof Float) {
return ((BigDecimal) wide).compareTo(BigDecimal.valueOf(narrow.doubleValue()));
return ((BigDecimal) wide).compareTo(new BigDecimal(narrow.toString()));
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dito: consistency

}

if(narrow instanceof RationalNumber) {
Expand All @@ -837,22 +842,23 @@ private int compareWideVsNarrow(
// at this point we know, that wide is one of {Double, Float}

if(narrow instanceof Double || narrow instanceof Float) {
return Double.compare(wide.doubleValue(), narrow.doubleValue());
return new BigDecimal(wide.toString())
.compareTo(new BigDecimal(narrow.toString()));
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dito: consistency

}

if(narrow instanceof RationalNumber) {
//TODO[220] can we do better than that, eg. by converting BigDecimal to RationalNumber
return BigDecimal.valueOf(wide.doubleValue())
return new BigDecimal(wide.toString())
.compareTo(((RationalNumber) narrow).bigDecimalValue());
}

if(narrow instanceof BigInteger) {
return BigDecimal.valueOf(wide.doubleValue())
return new BigDecimal(wide.toString())
.compareTo(new BigDecimal((BigInteger) narrow));
}

// at this point we know, that 'narrow' is one of {(Atomic)Long, (Atomic)Integer, Short, Byte}
return BigDecimal.valueOf(wide.doubleValue())
return new BigDecimal(wide.toString())
.compareTo(BigDecimal.valueOf(narrow.longValue()));

}
Expand Down
12 changes: 12 additions & 0 deletions src/main/java/tech/units/indriya/function/RationalNumber.java
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Expand Up @@ -123,6 +123,18 @@ public static RationalNumber of(double number) {
return of(decimalValue);
}

/**
* Returns a {@code RationalNumber} that represents the given float
* {@code number}, with an accuracy equivalent to {@code new BigDecimal(Float.toString(number))}.
*
* @param number
*/
public static RationalNumber of(float number) {
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As mentioned above, breaks the general scheme of first extending floats to double before converting them to BigDecimal or Rational.

// smh why does Java not have BigDecimal.valueOf(float) ?!
final BigDecimal decimalValue = new BigDecimal(Float.toString(number));
return of(decimalValue);
}

/**
* Returns a {@code RationalNumber} that represents the given BigDecimal decimalValue.
*
Expand Down
7 changes: 7 additions & 0 deletions src/test/java/tech/units/indriya/function/DoubleMultiplyConverterTest.java
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Expand Up @@ -52,6 +52,13 @@ public void testConvertMethod() {
assertEquals(-200, converter.convert(-100), 0.1);
}

@Test
public void testConvertMethodFloat() {
assertEquals(200, converter.convert(100f), 0.1);
assertEquals(0, converter.convert(0f));
assertEquals(-200, converter.convert(-100f), 0.1);
}

@Test
public void testEqualityOfTwoLogConverter() {
assertNotNull(converter);
Expand Down
26 changes: 26 additions & 0 deletions src/test/java/tech/units/indriya/function/UnitConverterTest.java
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Expand Up @@ -78,6 +78,24 @@ public void testQuantity() {
assertEquals(targetUnit, quantResult1.getUnit());
}

@Test
public void testQuantityDouble() {
Quantity<Length> quantLength1 = Quantities.getQuantity(1.56, sourceUnit);
Quantity<Length> quantResult1 = quantLength1.to(targetUnit);
assertNotNull(quantResult1);
assertNumberEquals(156, quantResult1.getValue(), 1E-12);
assertEquals(targetUnit, quantResult1.getUnit());
}

@Test
public void testQuantityFloat() {
Quantity<Length> quantLength1 = Quantities.getQuantity(1.56f, sourceUnit);
Quantity<Length> quantResult1 = quantLength1.to(targetUnit);
assertNotNull(quantResult1);
assertNumberEquals(156, quantResult1.getValue(), 1E-12);
assertEquals(targetUnit, quantResult1.getUnit());
}

@Test
public void testKelvinToCelsius() {
Quantity<Temperature> sut = Quantities.getQuantity(273.15d, KELVIN).to(CELSIUS);
Expand All @@ -86,6 +104,14 @@ public void testKelvinToCelsius() {
assertNumberEquals(0, sut.getValue(), 1E-12);
}

@Test
public void testKelvinToCelsiusFloat() {
Quantity<Temperature> sut = Quantities.getQuantity(273.15f, KELVIN).to(CELSIUS);
assertNotNull(sut);
assertEquals(CELSIUS, sut.getUnit());
assertNumberEquals(0, sut.getValue(), 1E-12);
}

@Test
public void testConverterTo() {
assertEquals(KILOGRAM.getConverterTo(KILO(GRAM)), KILO(GRAM).getConverterTo(KILOGRAM));
Expand Down