Question

Please fix this code so it compiles

import java.math.BigDecimal;

import java.lang.Math;

public class Sequence {

public static BigDecimal fact( int n ) {

BigDecimal result = BigDecimal.ONE;

while (n > 0) {

result = result.multiply(new BigDecimal(n + ""));

n--;

}

return result;

}

public static BigDecimal pow( BigDecimal a, int b ) {

BigDecimal result = a;

if(b == 0) {

return BigDecimal.ONE;

}

while ( b > 1 ) {

result = result.multiply(new BigDecimal(a + ""));

b--;

System.out.print("\n" + result + "\n");

}

return result;

}

public static BigDecimal Ramanujan( int n ) {

BigDecimal coefficient = BigDecimal.valueOf(Math.sqrt(8.0)).divide(BigDecimal.valueOf(9801)); //will multiply the sum by sqrt(8)/9801

BigDecimal pi_R = BigDecimal.ONE;

BigDecimal sum = BigDecimal.ZERO;

BigDecimal quotient;

BigDecimal numer;

BigDecimal denom;

for(int i = 0; i <= n; i++ ) {

BigDecimal bigN = BigDecimal.valueOf(n); //Now, when we need to do arithmetic with ints we can do that, and

//when we need arithmetic with BigDecimals we can do that.

numer = (BigDecimal.valueOf(26390).multiply(bigN));

numer = numer.add(BigDecimal.valueOf(1103));

numer = numer.multiply(fact( 4 * n ));

denom = pow( fact(n), 4 );

denom.multiply(pow(BigDecimal.valueOf(396), (4 * n)) );

quotient = numer.divide(denom);

sum.add(quotient);

}

pi_R = BigDecimal.ONE.divide(coefficient.multiply(sum));

return pi_R;

}

public static BigDecimal Chudnovsky( int n ) {

BigDecimal coefficient = BigDecimal.ONE.divide(BigDecimal.valueOf(53360.0).multiply(BigDecimal.valueOf(Math.sqrt(640320.0)))); //will multiply the sum by 1/53360sqrt(640320)

BigDecimal pi_C = BigDecimal.ONE;

BigDecimal sum = BigDecimal.ZERO;

BigDecimal quotient;

BigDecimal numer;

BigDecimal denom;

for(int i = 0; i <= n; i++ ) {

BigDecimal bigN = BigDecimal.valueOf(n);

numer = BigDecimal.valueOf(545140134).multiply(bigN);

numer = numer.add(BigDecimal.valueOf(13591409.0));

numer = numer.multiply(pow( BigDecimal.valueOf(-1), n ));

numer = numer.multiply(fact( 6 * n ));

denom = pow( fact(n), 3 );

denom = denom.multiply( fact( 3 * n ));

denom = denom.multiply( pow( BigDecimal.valueOf(340320), (3*n) ));

quotient = numer.divide(denom);

sum.add(quotient);

}

pi_C = BigDecimal.ONE.divide(coefficient.multiply(sum));

return pi_C;

}

public static void main(String[] args) {

BigDecimal ramanPi = Ramanujan(10000);

BigDecimal chudPi = Chudnovsky(10000);

System.out.print("Ramanujan's algorithm for pi, for n = 10,000:\n" + ramanPi + "\n");

System.out.print("Chudnovsky brothers' algorithm for pi, for n = 10,000:\n" + chudPi);

}

}

Answer 1

Hi,

Considering that algorithm is correct for pi calculation , if i have understood your question correctly you are facing compilation errors.

After i tried and executing above program,

I faced below compilation error,

Exception in thread "main" java.lang.ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.
   at java.math.BigDecimal.divide(BigDecimal.java:1690)
   at Sequence.Ramanujan(Sequence.java:50)
   at Sequence.main(Sequence.java:137)

this error for below lines,

1>

public static BigDecimal Ramanujan( int n ) {

BigDecimal coefficient = BigDecimal.valueOf(Math.sqrt(8.0)).divide(BigDecimal.valueOf(9801)); //will multiply the sum by sqrt(8)/9801

-----

}

solution:

When a MathContext object is supplied with a precision setting of 0 (for example, MathContext.UNLIMITED), arithmetic operations are exact, as are the arithmetic methods which take no MathContext object. (This is the only behavior that was supported in releases prior to 5.)

As a corollary of computing the exact result, the rounding mode setting of a MathContext object with a precision setting of 0 is not used and thus irrelevant. In the case of divide, the exact quotient could have an infinitely long decimal expansion; for example, 1 divided by 3.

If the quotient has a nonterminating decimal expansion and the operation is specified to return an exact result, an ArithmeticException is thrown. Otherwise, the exact result of the division is returned, as done for other operations.

you can find this explaination in java 8 docs also.

BigDecimal coefficient = BigDecimal.valueOf(Math.sqrt(8.0)).divide(BigDecimal.valueOf(9801),2,RoundingMode.HALF_UP);

where 2 is precision and RoundingMode.HALF_UP is rounding mode

RoundingMode are Enum constants, you could choose any of this UP, DOWN, CEILING, FLOOR, HALF_DOWN, HALF_EVEN, HALF_UP

In this Case HALF_UP, will have this result:

2.4 = 2   
2.5 = 3   
2.7 = 3

2>same things need to be corrected for

public static BigDecimal Chudnovsky( int n )
{

BigDecimal coefficient = BigDecimal.ONE.divide(BigDecimal.valueOf(53360.0).multiply(BigDecimal.valueOf(Math.sqrt(640320.0))),2,RoundingMode.HALF_EVEN);

-----

}

Thanks,

kindly upvote.