OpenMP-OpenMP'for'语句中的索引变量必须具有带符号的整数类型

Question

I'm new to OpenMP. I'm trying to use multiple cores for a for loop but I get this compiling error:

"error C3016: 'x' : index variable in OpenMP 'for' statement must have signed integral type".

I know OpenMP 2.0, which is standard with Microsoft Visual Studio 2010 ( what I'm using ), does not support unsigned data types for some reason but I don't believe I have any unsigned data types being used in this loop.

Here is how my code looks like:

Variable Declerations:

struct Vertex
{
    float x, y;
};

FractalGenerator::Vertex FractalGenerator::_fracStart;
FractalGenerator::Vertex FractalGenerator::_fracEnd;
float FractalGenerator::_pointPrecision = 0.008f;
float FractalGenerator::_scaleFactor = 1;

For Loop:

float _fracStep =  _pointPrecision / _scaleFactor;

#pragma omp parallel for
for (float x = _fracStart.x; x < _fracEnd.x; x += _fracStep)
{
    for (float y = _fracStart.y; y < _fracEnd.y; y += _fracStep)
    {

Answer 1

Looks like OpenMP doesn't support non-integral types as the index in a for loop. You have float x , and while float is an arithmetic type, it's not an integral type.

An integral type is one of: bool , char , char16_t , char32_t , wchar_t , and any of the signed and unsigned integer types ( char , short , int , long , and long long ).

You'll need to convert your algorithm to use one of these for the index of your for loop. This might work:

int iEnd = (_fracEnd.x - _fracStart.x) / _fracStep;
int jEnd = (_fracEnd.y - _fracStart.y) / _fracStep;
for (int i = 0; i < iEnd; i++)
{
  float x = _fracStart.x + i * _fracStep;
  for (int j = 0; j < jEnd; j++)
  {
    float y = _fracStart.y + j * _fracStep;
    // ...
  }
}