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ICU-13495 Optimizing chooseMultiplierAndApply method implementation.

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X-SVN-Rev: 40732
This commit is contained in:
Shane Carr 2017-12-14 00:47:43 +00:00
parent 6d9ed3698b
commit 5c054df085
5 changed files with 99 additions and 30 deletions
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43
icu4c/source/i18n/number_rounding.cpp
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@ -251,28 +251,39 @@ void Rounder::setLocaleData(const CurrencyUnit &currency, UErrorCode &status) {
int32_t
Rounder::chooseMultiplierAndApply(impl::DecimalQuantity &input, const impl::MultiplierProducer &producer,
UErrorCode &status) {
// TODO: Make a better and more efficient implementation.
// TODO: Avoid the object creation here.
DecimalQuantity copy(input);
// Do not call this method with zero.
U_ASSERT(!input.isZero());
int32_t magnitude = input.getMagnitude();
int32_t multiplier = producer.getMultiplier(magnitude);
// Perform the first attempt at rounding.
int magnitude = input.getMagnitude();
int multiplier = producer.getMultiplier(magnitude);
input.adjustMagnitude(multiplier);
apply(input, status);
// If the number turned to zero when rounding, do not re-attempt the rounding.
if (!input.isZero() && input.getMagnitude() == magnitude + multiplier + 1) {
magnitude += 1;
input = copy;
multiplier = producer.getMultiplier(magnitude);
input.adjustMagnitude(multiplier);
U_ASSERT(input.getMagnitude() == magnitude + multiplier - 1);
apply(input, status);
U_ASSERT(input.getMagnitude() == magnitude + multiplier);
// If the number rounded to zero, exit.
if (input.isZero() || U_FAILURE(status)) {
return multiplier;
}
return multiplier;
// If the new magnitude after rounding is the same as it was before rounding, then we are done.
// This case applies to most numbers.
if (input.getMagnitude() == magnitude + multiplier) {
return multiplier;
}
// If the above case DIDN'T apply, then we have a case like 99.9 -> 100 or 999.9 -> 1000:
// The number rounded up to the next magnitude. Check if the multiplier changes; if it doesn't,
// we do not need to make any more adjustments.
int _multiplier = producer.getMultiplier(magnitude + 1);
if (multiplier == _multiplier) {
return multiplier;
}
// We have a case like 999.9 -> 1000, where the correct output is "1K", not "1000".
// Fix the magnitude and re-apply the rounding strategy.
input.adjustMagnitude(_multiplier - multiplier);
apply(input, status);
return _multiplier;
}
/** This is the method that contains the actual rounding logic. */

11
icu4c/source/i18n/number_types.h
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@ -230,10 +230,21 @@ class U_I18N_API MicroPropsGenerator {
virtual void processQuantity(DecimalQuantity& quantity, MicroProps& micros, UErrorCode& status) const = 0;
};
/**
* An interface used by compact notation and scientific notation to choose a multiplier while rounding.
*/
class MultiplierProducer {
public:
virtual ~MultiplierProducer() = default;
/**
* Maps a magnitude to a multiplier in powers of ten. For example, in compact notation in English, a magnitude of 5
* (e.g., 100,000) should return a multiplier of -3, since the number is displayed in thousands.
*
* @param magnitude
* The power of ten of the input number.
* @return The shift in powers of ten.
*/
virtual int32_t getMultiplier(int32_t magnitude) const = 0;
};

14
icu4c/source/i18n/unicode/numberformatter.h
View File

@ -836,6 +836,20 @@ class U_I18N_API Rounder : public UMemory {
/** Version of {@link #apply} that obeys minInt constraints. Used for scientific notation compatibility mode. */
void apply(impl::DecimalQuantity &value, int32_t minInt, UErrorCode status);
/**
* Rounding endpoint used by Engineering and Compact notation. Chooses the most appropriate multiplier (magnitude
* adjustment), applies the adjustment, rounds, and returns the chosen multiplier.
*
* <p>
* In most cases, this is simple. However, when rounding the number causes it to cross a multiplier boundary, we
* need to re-do the rounding. For example, to display 999,999 in Engineering notation with 2 sigfigs, first you
* guess the multiplier to be -3. However, then you end up getting 1000E3, which is not the correct output. You then
* change your multiplier to be -6, and you get 1.0E6, which is correct.
*
* @param input The quantity to process.
* @param producer Function to call to return a multiplier based on a magnitude.
* @return The number of orders of magnitude the input was adjusted by this method.
*/
int32_t
chooseMultiplierAndApply(impl::DecimalQuantity &input, const impl::MultiplierProducer &producer,
UErrorCode &status);

8
icu4j/main/classes/core/src/com/ibm/icu/impl/number/MultiplierProducer.java
View File

@ -6,5 +6,13 @@ package com.ibm.icu.impl.number;
* An interface used by compact notation and scientific notation to choose a multiplier while rounding.
*/
public interface MultiplierProducer {
/**
* Maps a magnitude to a multiplier in powers of ten. For example, in compact notation in English, a magnitude of 5
* (e.g., 100,000) should return a multiplier of -3, since the number is displayed in thousands.
*
* @param magnitude
* The power of ten of the input number.
* @return The shift in powers of ten.
*/
int getMultiplier(int magnitude);
}

53
icu4j/main/classes/core/src/com/ibm/icu/number/Rounder.java
View File

@ -485,29 +485,54 @@ public abstract class Rounder implements Cloneable {
}
}
/**
* Rounding endpoint used by Engineering and Compact notation. Chooses the most appropriate multiplier (magnitude
* adjustment), applies the adjustment, rounds, and returns the chosen multiplier.
*
* <p>
* In most cases, this is simple. However, when rounding the number causes it to cross a multiplier boundary, we
* need to re-do the rounding. For example, to display 999,999 in Engineering notation with 2 sigfigs, first you
* guess the multiplier to be -3. However, then you end up getting 1000E3, which is not the correct output. You then
* change your multiplier to be -6, and you get 1.0E6, which is correct.
*
* @param input The quantity to process.
* @param producer Function to call to return a multiplier based on a magnitude.
* @return The number of orders of magnitude the input was adjusted by this method.
*/
int chooseMultiplierAndApply(DecimalQuantity input, MultiplierProducer producer) {
// TODO: Make a better and more efficient implementation.
// TODO: Avoid the object creation here.
DecimalQuantity copy = input.createCopy();
// Do not call this method with zero.
assert !input.isZero();
// Perform the first attempt at rounding.
int magnitude = input.getMagnitude();
int multiplier = producer.getMultiplier(magnitude);
input.adjustMagnitude(multiplier);
apply(input);
// If the number turned to zero when rounding, do not re-attempt the rounding.
if (!input.isZero() && input.getMagnitude() == magnitude + multiplier + 1) {
magnitude += 1;
input.copyFrom(copy);
multiplier = producer.getMultiplier(magnitude);
input.adjustMagnitude(multiplier);
assert input.getMagnitude() == magnitude + multiplier - 1;
apply(input);
assert input.getMagnitude() == magnitude + multiplier;
// If the number rounded to zero, exit.
if (input.isZero()) {
return multiplier;
}
return multiplier;
// If the new magnitude after rounding is the same as it was before rounding, then we are done.
// This case applies to most numbers.
if (input.getMagnitude() == magnitude + multiplier) {
return multiplier;
}
// If the above case DIDN'T apply, then we have a case like 99.9 -> 100 or 999.9 -> 1000:
// The number rounded up to the next magnitude. Check if the multiplier changes; if it doesn't,
// we do not need to make any more adjustments.
int _multiplier = producer.getMultiplier(magnitude + 1);
if (multiplier == _multiplier) {
return multiplier;
}
// We have a case like 999.9 -> 1000, where the correct output is "1K", not "1000".
// Fix the magnitude and re-apply the rounding strategy.
input.adjustMagnitude(_multiplier - multiplier);
apply(input);
return _multiplier;
}
///////////////