Of course, an interpreted language implementation, versus a compiled language designed to port UNIX.
Even if counting that it is basically calling into C or C++ libraries, there is lots of boilerplate that the CPU has to consume, that just won't happen on the pure C implementation.
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Check out this port of microgpt to C, posted 5 months ago. It got a 2500x speedup over the python version. https://github.com/moebiusV/cugpt
In the README, the C version gets "452× faster than Python", the 2500x one is using OpenBLAS which uses lower level things than what's in C[1].
[1] see eg https://github.com/OpenMathLib/OpenBLAS/tree/develop/kernel/...
Of course, an interpreted language implementation, versus a compiled language designed to port UNIX.
Even if counting that it is basically calling into C or C++ libraries, there is lots of boilerplate that the CPU has to consume, that just won't happen on the pure C implementation.