...algorithmically equivalent to being able to write the code. Here's a proof:
First define SPEC(X,Y) to be the specification "Find the most efficient piece of C code starting with the code X that fulfils specification Y".

Then we can define TIME(Z) to be the time it takes to implement specification Z. For example TIME(SPEC("#inclu","Print out 'Hello, World!'")) is of the order of seconds.

So suppose you are given a specification X. Evaluate TIME(SPEC("a",X)), TIME(SPEC("b",X)), TIME(SPEC("c",X)), ... Go through all 256 ASCII characters, not just the alphabet. Now pick the first argument of SPEC() that gives the smallest of these values. That is now the first character of your code. Suppose, for example, the first character is '#'. Now evaluate TIME(SPEC("#a",X)), TIME(SPEC("#a",Y)), ...

I think you can all see how it goes. So having an algorithm to estimate schedules implies you have an algorithm to write code.

But that's not all! We know there is no algorithm to automatically write code (halting problem 'n' all that). Therefore there is no algorithm to estimate schedules. So this is another proof of what the article claims.