Especially in the field that you're asking about, these do not mean the same thing.
In any sort of computational processing, if you were to say that something is "not reasonable," the conclusion drawn is that what is being proposed is a very inefficient method. It likely is technically a correct method, but it is not reasonable for the use case.
For example, here is one approach for checking if a number is prime:
- x = 2
- Divide number by x
- If the remainder is 1, return false
- Increment x by 1 and go back to step 2
- If x gets to input - 1 and we haven't returned false yet, return true
This is technically a correct approach, however it is grossly inefficient and impractical if you are working with bigger numbers. A more efficient approach would be the implementing the Sieve of Eratosthenes, which I won't explain on here as this is a site about English :).
The method I outlined above DOES make sense, but it is not reasonable for working with bigger numbers. So if you were trying to brute force some sort of encryption that uses big prime numbers, you'd be waiting for thousands of years for your calculations to finish.
On the other hand, if I outlined this method for finding out if a number is prime or not:
- Flip a coin. If it is sunny out and the coin lands on its side, your number is prime! Otherwise, it is false.
Then you would be able to say that this method does not make sense.
Even in general, when not referring to computer science applications, these two phrases are not mutually inclusive.