Suggestion : writing 'sign' and 'grade' in WebAssembly

[grondilu]

Hello,

for better performance, it may be desirable to port this library to WebAssembly.

It is a bit early to try to port the whole thing, but two crucial functions can already be ported easily : 'sign' and 'grade'. It is my understanding that those two functions are a performance bottleneck, so they may be worth implementing right now.

The following C code can be compiled for instance with the WASM explorer:

typedef unsigned long int integer;
int grade(integer b);

int sign(integer a, integer b) {
  integer n = a >> 1;
  int sum = 0;
  while (n != 0) {
    sum += grade(n & b);
    n >>= 1;
  }
  return sum&1 ? -1 : 1;
}

int grade(integer b) {
  unsigned int n = 0;
  while (b != 0) {
    if (b&1) { n++; }
    b >>= 1;
  }
  return n;
}

That would limit the number of vector dimensions to 32 (or 64 if we really want that), but who needs more than 32 vector dimensions anyway?