My goal is to generate random numbers that all have decimal precision errors.
Here are some examples of types of numbers I would like to generate:
1.8181818723678589 1.2727272510528564 0.444444477558136
Here are strategies I have tried.
None of the things I tried have created even a single number similar to that which I am looking for.
Assuming that the exact values actually meant are:
- 1.81 repeating
- 1.27 repeating
- 0.4 repeating
Observe that in each number there are around 7 or 8 digits that are “correct”, and around 18 digits in total.
floats are usually precise to 7 to 8 digits, and
doubles are usually precise to around 18 digits, so I suspect that these numbers are actually
floats (or 32-bit floating point numbers) that got “widened” to be
1.81 repeating is 20/11, so I tried:
float i = 20f/11f; double d = i; System.out.println(d);
This prints exactly the value you saw – 1.8181818723678589.
1.27 repeating is 14/11 and 0.4 repeating is 4/9. You can try both of these yourself. They all produce your desired numbers. This strongly suggests that the errors are produced by widening a
float to 64 bits.