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opencl: adjust threads and blocks options. #20

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opencl: adjust threads and blocks options. #20

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63 changes: 60 additions & 3 deletions src/opencl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -239,6 +239,46 @@ hs_opencl_run(
exit(1);
};

/* Query the max work group size. */
size_t max_wg_size = 0;
err = clGetDeviceInfo(dids[options->device], CL_DEVICE_MAX_WORK_GROUP_SIZE,
sizeof(size_t), &max_wg_size, NULL);

if (err != CL_SUCCESS) {
printf("failed to get CL_DEVICE_MAX_WORK_GROUP_SIZE: %d\n", err);
free(dids);
exit(1);
}

/* Query the max work item dimensions. */
size_t max_wi_dim;
err = clGetDeviceInfo(dids[options->device],
CL_DEVICE_MAX_WORK_ITEM_DIMENSIONS, sizeof(max_wi_dim), &max_wi_dim, NULL);

if (err != CL_SUCCESS) {
printf("failed to get CL_DEVICE_MAX_WORK_ITEM_DIMENSIONS: %d\n", err);
free(dids);
exit(1);
}

/* Query the max work item size for each dimension. */
size_t *max_wi_size = (size_t *)malloc(sizeof(size_t) * max_wi_dim);
err = clGetDeviceInfo(dids[options->device], CL_DEVICE_MAX_WORK_ITEM_SIZES,
sizeof(size_t) * max_wi_dim, max_wi_size, NULL);

if (err != CL_SUCCESS) {
printf("failed to get CL_DEVICE_MAX_WORK_ITEM_SIZES: %d\n", err);
free(max_wi_size);
free(dids);
exit(1);
}

/* Calculate the max work items for the device. */
size_t max_work_items = 1;
for (size_t i = 0; i < max_wi_dim; i++)
max_work_items *= max_wi_size[i];

free(max_wi_size);
free(dids);

/* Create a kernel. */
Expand All @@ -259,12 +299,29 @@ hs_opencl_run(
exit(1);
}

size_t global_size = options->threads;
size_t local_size = options->blocks;
size_t total_work_items = options->threads;
size_t work_group_size = options->blocks;

if (total_work_items > max_work_items || total_work_items < 1)
total_work_items = max_work_items;

if (work_group_size > max_wg_size || work_group_size < 1)
work_group_size = max_wg_size;

/**
* If total_work_items is not divisible by work_group_size,
* we need to lower total_work_items to the next multiple
* of work_group_size.
*/
if (total_work_items % work_group_size != 0)
total_work_items = total_work_items / work_group_size * work_group_size;

printf("Total work items: %lu\n", total_work_items);
printf("Work group size: %lu\n", work_group_size);

/* Enqueue kernel. */
err = clEnqueueNDRangeKernel(queue, kernel, 1, NULL,
&global_size, &local_size, 0, NULL, NULL);
&total_work_items, &work_group_size, 0, NULL, NULL);

if (err != CL_SUCCESS) {
printf("failed to enqueue the kernel: %d\n", err);
Expand Down