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Add MatrixUtil for matrix operations (#2798)

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Co-authored-by: xzero <andrejmezler@yahoo.de>
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caos321 2021-11-02 07:06:25 +01:00 committed by GitHub
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package Maths;
import java.math.BigDecimal;
import java.util.Arrays;
import java.util.Objects;
import java.util.Optional;
import java.util.function.BiFunction;
import java.util.stream.IntStream;
/**
* @author: caos321
* @date: 31 October 2021 (Sunday)
*/
public class MatrixUtil {
public static boolean isValid(final BigDecimal[][] matrix) {
return matrix != null && matrix.length > 0 && matrix[0].length > 0;
}
public static boolean hasEqualSizes(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) {
return isValid(matrix1) && isValid(matrix2)
&& matrix1.length == matrix2.length
&& matrix1[0].length == matrix2[0].length;
}
public static boolean canMultiply(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) {
return isValid(matrix1) && isValid(matrix2)
&& matrix1[0].length == matrix2.length;
}
public static Optional<BigDecimal[][]> operate(final BigDecimal[][] matrix1,
final BigDecimal[][] matrix2,
final BiFunction<BigDecimal, BigDecimal, BigDecimal> operation) {
if (!hasEqualSizes(matrix1, matrix2)) {
return Optional.empty();
}
final int rowSize = matrix1.length;
final int columnSize = matrix1[0].length;
final BigDecimal[][] result = new BigDecimal[rowSize][columnSize];
IntStream.range(0, rowSize).forEach(rowIndex ->
IntStream.range(0, columnSize).forEach(columnIndex -> {
final BigDecimal value1 = matrix1[rowIndex][columnIndex];
final BigDecimal value2 = matrix2[rowIndex][columnIndex];
result[rowIndex][columnIndex] = operation.apply(value1, value2);
}));
return Optional.of(result);
}
public static Optional<BigDecimal[][]> add(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) {
return operate(matrix1, matrix2, BigDecimal::add);
}
public static Optional<BigDecimal[][]> subtract(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) {
return operate(matrix1, matrix2, BigDecimal::subtract);
}
public static Optional<BigDecimal[][]> multiply(final BigDecimal[][] matrix1, final BigDecimal[][] matrix2) {
if (!canMultiply(matrix1, matrix2)) {
return Optional.empty();
}
final int size = matrix1[0].length;
final int matrix1RowSize = matrix1.length;
final int matrix2ColumnSize = matrix2[0].length;
final BigDecimal[][] result = new BigDecimal[matrix1RowSize][matrix2ColumnSize];
IntStream.range(0, matrix1RowSize).forEach(rowIndex ->
IntStream.range(0, matrix2ColumnSize).forEach(columnIndex ->
result[rowIndex][columnIndex] = IntStream.range(0, size).mapToObj(index -> {
final BigDecimal value1 = matrix1[rowIndex][index];
final BigDecimal value2 = matrix2[index][columnIndex];
return value1.multiply(value2);
})
.reduce(BigDecimal.ZERO, BigDecimal::add)
)
);
return Optional.of(result);
}
public static void assertThat(final BigDecimal[][] actual, final BigDecimal[][] expected) {
if (!Objects.deepEquals(actual, expected)) {
throw new AssertionError(String.format(
"expected=%s but was actual=%s",
Arrays.deepToString(expected),
Arrays.deepToString(actual)
));
}
}
public static void main(final String[] args) {
{
final BigDecimal[][] matrix1 = {
{new BigDecimal(3), new BigDecimal(2)},
{new BigDecimal(0), new BigDecimal(1)},
};
final BigDecimal[][] matrix2 = {
{new BigDecimal(1), new BigDecimal(3)},
{new BigDecimal(2), new BigDecimal(0)},
};
final BigDecimal[][] actual = add(matrix1, matrix2)
.orElseThrow(() -> new AssertionError("Could not compute matrix!"));
final BigDecimal[][] expected = {
{new BigDecimal(4), new BigDecimal(5)},
{new BigDecimal(2), new BigDecimal(1)}
};
assertThat(actual, expected);
}
{
final BigDecimal[][] matrix1 = {
{new BigDecimal(1), new BigDecimal(4)},
{new BigDecimal(5), new BigDecimal(6)},
};
final BigDecimal[][] matrix2 = {
{new BigDecimal(2), new BigDecimal(0)},
{new BigDecimal(-2), new BigDecimal(-3)},
};
final BigDecimal[][] actual = subtract(matrix1, matrix2)
.orElseThrow(() -> new AssertionError("Could not compute matrix!"));
final BigDecimal[][] expected = {
{new BigDecimal(-1), new BigDecimal(4)},
{new BigDecimal(7), new BigDecimal(9)}
};
assertThat(actual, expected);
}
{
final BigDecimal[][] matrix1 = {
{new BigDecimal(1), new BigDecimal(2), new BigDecimal(3)},
{new BigDecimal(4), new BigDecimal(5), new BigDecimal(6)},
{new BigDecimal(7), new BigDecimal(8), new BigDecimal(9)}
};
final BigDecimal[][] matrix2 = {
{new BigDecimal(1), new BigDecimal(2)},
{new BigDecimal(3), new BigDecimal(4)},
{new BigDecimal(5), new BigDecimal(6)}
};
final BigDecimal[][] actual = multiply(matrix1, matrix2)
.orElseThrow(() -> new AssertionError("Could not compute matrix!"));
final BigDecimal[][] expected = {
{new BigDecimal(22), new BigDecimal(28)},
{new BigDecimal(49), new BigDecimal(64)},
{new BigDecimal(76), new BigDecimal(100)}
};
assertThat(actual, expected);
}
}
}