GAP Message (Diagnostic ID 30533)

Message

Compile with the %s option to vectorize and/or parallelize the loop at line %d.

Advice

Use the [Q]opt-subscript-in-range option for the specified file during compilation.

This option helps the compiler vectorize and parallelize the loop at the specified line. You must verify that the loops in the file do not contain very large integers and are not likely to generate very large integers in intermediate computations. A very large integer is loosely defined as follows: On an n-bit machine, a very large integer is typically >= 2^n-2. For example, on a 32-bit machine, a very large integer would be >= 2³⁰.

Example

Consider the following:

int f(int* A, int upper1, int upper2){
  long extra = 100.0;
  int return_val = 0;
  int val;
  for(int j=0; j < upper1; j++){
    for(int i = 0; i < upper2; i++){
      val = A[i*extra];
      return_val += val;
    }
  }
  return return_val; 
}

If you determine it is safe to do so, compiling this example with the [Q]opt-subscript-in-range option results in vectorization of the innermost loop.

Verify

Confirm that no loop in the program contains or generates very large integers (typically very large integers are >= 2³⁰).