No, it's not. Maybe only faster than when I bash it jokingly, using hyperbole (it won't take eternity for Ruby to do things that C# computes in a moment, only a half of it)
On the content of the post:
"Now it’s Ruby that’s 5 times faster than Crystal!!! And 20x faster than our original version. Though most likely that’s some cost from the FFI, or something similar, though that does seem like a surprising amount of overhead."
There are tools to provide a definitive answer to this, and no, FFI is not a silver bullet solution to slowness of interpreted (or JIT compiled but dynamically typed) languages.
On the content of the post: "Now it’s Ruby that’s 5 times faster than Crystal!!! And 20x faster than our original version. Though most likely that’s some cost from the FFI, or something similar, though that does seem like a surprising amount of overhead."
There are tools to provide a definitive answer to this, and no, FFI is not a silver bullet solution to slowness of interpreted (or JIT compiled but dynamically typed) languages.