获得模数和除法结果的最佳方法？

Question

Seeing as modulo and integer division are closely related, you'd think it would make sense to get both values in one operation. Are there languages that have this capability?

Follow up question: For languages that don't have this capability, is it best to compute the modulo by subtracting off the result of the division * denominator?

// In java, if I want both values I need to do this:
int myNumber = 125;
int denominator = 6;

int division = myNumber / denominator;  // 20
int modulo1   = myNumber % denominator;  // 5

// Follow up: Is this a more efficient way to compute the modulo?
int modulo2 = myNumber - division * denominator;

Answer 1

When you use BigInteger , you can query quotient and remainder in one operation

BigInteger myNumber = BigInteger.valueOf(125), denominator = BigInteger.valueOf(6);
BigInteger[] result = myNumber.divideAndRemainder(denominator);
System.out.println(myNumber + " / " + denominator + " = " + result[0]);
System.out.println(myNumber + " % " + denominator + " = " + result[1]);

125 / 6 = 20
125 % 6 = 5

However, when you are calculating with integral values, it's best to trust the JIT compiler/ hotspot optimizer.

Eg when I use

static void test(int myNumber, int denominator) {
    int division = myNumber / denominator;  // 20
    int modulo1   = myNumber % denominator;  // 5

    // prevent over-optimization
    if(division != 20 || modulo1 != 5) throw new AssertionError();
}

and run test(125, 6) often enough, I get the following compiled native code with JDK 11/x86

  0x0000029f3ef97b2c: mov     eax,edx
  0x0000029f3ef97b2e: test    r8d,r8d
  0x0000029f3ef97b31: je      29f3ef97b63h      ;*idiv {reexecute=0 rethrow=0 return_oop=0}
                                                ; - SO71326541::test@2 (line 23)

  0x0000029f3ef97b33: cmp     eax,80000000h
  0x0000029f3ef97b38: jne     29f3ef97b42h
  0x0000029f3ef97b3a: xor     edx,edx
  0x0000029f3ef97b3c: cmp     r8d,0ffffffffh
  0x0000029f3ef97b40: je      29f3ef97b46h
  0x0000029f3ef97b42: cdq
  0x0000029f3ef97b43: idiv    eax,r8d
  0x0000029f3ef97b46: mov     r11d,edx
  0x0000029f3ef97b49: cmp     eax,14h
  0x0000029f3ef97b4c: jne     29f3ef97b72h      ;*if_icmpne {reexecute=0 rethrow=0 return_oop=0}
                                                ; - SO71326541::test@11 (line 27)

  0x0000029f3ef97b4e: cmp     edx,5h
  0x0000029f3ef97b51: jne     29f3ef97b86h      ;*if_icmpeq {reexecute=0 rethrow=0 return_oop=0}
                                                ; - SO71326541::test@16 (line 27)

We can clearly see that the two operations, myNumber / denominator and myNumber % denominator have been fused into a single idiv instruction.