ICC compiler - error: parallel loop condition does not test loop control variable

I am trying to parallelize a "for loop" of my C/OpenMP code, after offload call on Intel MIC (Xeon Phi) card. I am using "#pragma omp parallel for" and it compiles good when I use an integer variable as "loop control variable". On my code I am using a float array as "loop control variable" and then I get the error "parallel loop condition does not test loop control variable".

Code with no error:

#define MAX_DIMENSIONS  10

unsigned long long  i,y=0;

#pragma offload target(mic) in(i,y)
{
    #pragma omp parallel for
    for(i=0;i<10;i++)
        /* code here */  
}

Code with error:

#define MAX_DIMENSIONS  10

float   x[MAX_DIMENSIONS];
unsigned long long  i,y=0;

#pragma offload target(mic) in(x[MAX_DIMENSIONS],i,y)
{
    #pragma omp parallel for
    for(x[0]=0.000000; x[0]<10.000000; x[0]+=1.000000)
        /* code here */
}

Is there any way to keep that float array notation in "for loop" in order to succeed the parallelization using OpenMP?

Solution

You can implement the working sharing manually like this

#pragma omp parallel
{
    float a = 0., b = 10.;
    float step = 1.;
    int N = (b-a)/step;
    int ithread = omp_get_thread_num();
    int nthreads = omp_get_num_threads();
    float t0 = (ithread+0)*N/nthreads + a;
    float t1 = (ithread+1)*N/nthreads + a;
    for(float x=t0; x<t1; x += step) {
      //code
    }
}

This would be equivalent to

#pragma omp parallel for 
for(float x=a; x<b; x += step)

if the omp for construct supported floating point iterators. For other schedules such as dynamic you have to implement them differently. Note that it's possible the parallel code and then sequential code don't give the same result e.g. if (b-a)/step has a fractional part (but (10.-0)/1. = 10. is okay). Therefore it's probably best to change your code to use integer iterators to be safe.