source code
// The Computer Language Benchmarks Game
// https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
//
// Translated from Mr Ledrug's C program by Jeremy Zerfas.
final class pidigits extends Java_GMP_Wrapper{
// These variables are used to store pointers to the GMP numbers we will be
// using in this program. These pointers are being stored as Java 64 bit
// signed longs and this could potentially cause a few problems. One problem
// could occur if the program is ran on a computer that is using more than
// 64 bits of address space. The second problem that could possibly occur is
// that the pointers could be corrupted while being converted to and from
// Java longs (if the machine architecture and/or C implementation is
// weird). Neither of these problems is likely to occur on just about any
// present day computer capable of running Java and if it is a problem you
// could work around it by storing the pointers in Java ByteBuffers or byte
// arrays (but those are about 5% slower from my testing and also increase
// the code size).
static final long tmp1_Pointer=allocate_mpz_t(),
tmp2_Pointer=allocate_mpz_t(), acc_Pointer=allocate_mpz_t(),
den_Pointer=allocate_mpz_t(), num_Pointer=allocate_mpz_t();
static final long extract_Digit(final long nth){
// joggling between tmp1_Pointer and tmp2_Pointer, so GMP won't have to
// use temp buffers
mpz_mul_ui(tmp1_Pointer, num_Pointer, nth);
mpz_add(tmp2_Pointer, tmp1_Pointer, acc_Pointer);
mpz_tdiv_q(tmp1_Pointer, tmp2_Pointer, den_Pointer);
return mpz_get_ui(tmp1_Pointer);
}
static final void eliminate_Digit(final long d){
mpz_submul_ui(acc_Pointer, den_Pointer, d);
mpz_mul_ui(acc_Pointer, acc_Pointer, 10);
mpz_mul_ui(num_Pointer, num_Pointer, 10);
}
static final void next_Term(final long k){
final long k2=k*2+1;
mpz_addmul_ui(acc_Pointer, num_Pointer, 2);
mpz_mul_ui(acc_Pointer, acc_Pointer, k2);
mpz_mul_ui(den_Pointer, den_Pointer, k2);
mpz_mul_ui(num_Pointer, num_Pointer, k);
}
public static final void main(final String[] args){
final long n=Long.parseLong(args[0]);
mpz_init_set_ui(tmp1_Pointer, 0);
mpz_init_set_ui(tmp2_Pointer, 0);
mpz_init_set_ui(acc_Pointer, 0);
mpz_init_set_ui(den_Pointer, 1);
mpz_init_set_ui(num_Pointer, 1);
// It's considerably faster to use a StringBuilder to buffer all the
// output and do one single print() call instead of many print(ln)()
// calls. A BufferedWriter could be used alternatively and works about
// equally well and is a little more flexible but it also increases the
// code size too.
final StringBuilder results=new StringBuilder();
for(long i=0, k=0; i<n;){
next_Term(++k);
if(mpz_cmp(num_Pointer, acc_Pointer)>0)
continue;
final long d=extract_Digit(3);
if(d!=extract_Digit(4))
continue;
results.append(d);
if(++i%10==0)
results.append("\t:").append(i).append("\n");
eliminate_Digit(d);
}
System.out.print(results);
}
}
class Java_GMP_Wrapper{
static {
System.loadLibrary("Java_GMP_Wrapper");
}
// Note that the following *_ui() functions will be calling GMP functions of
// the same name and they will be expecting C unsigned longs (which are at
// least 32 bits in size) but we'll actually be passing them Java signed
// longs (which are 64 bits). All of these functions except for
// mpz_addmul_ui() and mpz_submul_ui() have a _si vesion that uses signed
// longs instead but I just decided to use the _ui versions for all of these
// anyway to be consistent with the original C program this was translated
// from and since I already had no choice for the mpz_addmul_ui() and
// mpz_submul_ui() functions. This shouldn't be an issue as long as the
// machine architecture and/or C implementation isn't weird which is the
// case for just about every present day computer capable of running Java.
//
// Also see the comment up above regarding the pointers.
final static native long allocate_mpz_t();
final static native void mpz_add(long sum_Pointer, long augend_Pointer,
long addend_Pointer);
final static native void mpz_addmul_ui(long sum_Pointer,
long multiplier_Pointer, long multiplicand);
final static native int mpz_cmp(long first_Number_Pointer,
long second_Number_Pointer);
final static native long mpz_get_ui(long number_Pointer);
final static native void mpz_init_set_ui(long number_Pointer,
long new_Value);
final static native void mpz_mul_ui(long product_Pointer,
long multiplier_Pointer, long multiplicand);
final static native void mpz_submul_ui(long difference_Pointer,
long minuend_Pointer, long subtrahend);
final static native void mpz_tdiv_q(long quotient_Pointer,
long dividend_Pointer, long divisor_Pointer);
}
notes, command-line, and program output
NOTES:
64-bit Ubuntu quad core
java 23 2024-09-17
Java HotSpot(TM) 64-Bit Server VM
(build 23+37-2369,
interpreted mode, sharing)
Mon, 17 Feb 2025 04:14:32 GMT
MAKE:
mv pidigits.javaxint-3.javaxint pidigits.java
/opt/src/jdk-23/bin/javac -d . -cp . --source-path Include/java pidigits.java
1.61 seconds to complete and log all make actions
COMMAND LINE:
/opt/src/jdk-23/bin/java -Xint -cp . pidigits 2000
EMPTY
PROGRAM OUTPUT:
Exception in thread "main" java.lang.UnsatisfiedLinkError: no Java_GMP_Wrapper in java.library.path: /usr/java/packages/lib:/usr/lib64:/lib64:/lib:/usr/lib
at java.base/java.lang.ClassLoader.loadLibrary(ClassLoader.java:2442)
at java.base/java.lang.Runtime.loadLibrary0(Runtime.java:916)
at java.base/java.lang.System.loadLibrary(System.java:2066)
at Java_GMP_Wrapper.<clinit>(pidigits.java:90)