CODEWITHSUNDEEP
openclpyopenclcl
Jaime Perez
Jaime Perez

Reputation: 109

I get wrong output when adding arrays with opencl

I'm trying to sum 2 arrays with pyopencl, but I get strange numbers in output.

Code:

def sum_arrays_with_cl(array1, array2):
"""
    Sums 2 arrays with GPU. 
"""
ctx = cl.create_some_context()
queue = cl.CommandQueue(ctx)
mf = cl.mem_flags
a_array = numpy.array(array1)
b_array = numpy.array(array2)
a_buf = cl.Buffer(ctx, mf.READ_ONLY | mf.COPY_HOST_PTR, hostbuf=a_array)
b_buf = cl.Buffer(ctx, mf.READ_ONLY | mf.COPY_HOST_PTR, hostbuf=b_array)
dest_buf = cl.Buffer(ctx, mf.WRITE_ONLY, b_array.nbytes)
prg = cl.Program(ctx, """
__kernel void sum(__global const float *a,
__global const float *b, __global float *res_g)
{
  int gid = get_global_id(0);
  res_g[gid] = a[gid] + b[gid];
}
""").build()
prg.sum(queue, a_array.shape, None, a_buf, b_buf, dest_buf)
a_plus_b = numpy.empty_like(a_array)
cl.enqueue_copy(queue, a_plus_b, dest_buf).wait()
return list(a_plus_b)

a = [1 for dummy in range(10)] b = [i for i in range(10)]

print sum_arrays_with_cl(a,b)

output:

[0, 0, 0, 0, 0, 5, 6, 7, 8, 9]

What I'm doing wrongly?

Upvotes: 0

Views: 128

Answers (1)

jprice
jprice

Reputation: 9925

You need to be explicit about the types of your arrays, otherwise the arrays created on the host won't match what the device expects. Since your kernel is expecting 32-bit floating point data, you can create your arrays like this:

a_array = numpy.array(array1).astype(numpy.float32)
b_array = numpy.array(array2).astype(numpy.float32)

Upvotes: 2

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