initial checkin

+arrayadd

+CFLAGS += -std=c99 -I/usr/local/include
+LIBS += -lcl -L/usr/local/lib64/beignet
+CC = cc
+
+all:
+	$(CC) -O2 -march=native $(CFLAGS) $(LIBS) -o arrayadd arrayadd.c

+# OpenCL array add.
+
+Taken from
+[here](http://www.heterogeneouscompute.org/wordpress/wp-content/uploads/2011/06/Chapter2.txt).
+
+## Description
+
+This is an example on how to implement an array add with OpenCL.
+
+## Requirements
+
+Some OpenCL capable hardware and the according OpenCL library exposing the
+OpenCL API. I tested this on an Intel GPU (Intel Corporation Haswell-ULT
+Integrated Graphics Controller (rev 09)) with the
+[beignet](https://www.freedesktop.org/wiki/Software/Beignet/)
+open source library.
+
+## License
+
+unknown

+OpenCL tutorial notes
+=====================
+
+URL: http://www.heterogeneouscompute.org/wordpress/wp-content/uploads/2011/06/Chapter2.txt

+// This program implements a vector addition using OpenCL
+
+// System includes
+#include <stdio.h>
+#include <stdlib.h>
+
+// OpenCL includes
+#include <CL/cl.h>
+
+// OpenCL kernel to perform an element-wise add of two arrays
+const char* programSource =
+"__kernel                                            \n"
+"void vecadd(__global int *A,                        \n"
+"            __global int *B,                        \n"
+"            __global int *C)                        \n"
+"{                                                   \n"
+"                                                    \n"
+"   // Get the work-item’s unique ID                 \n"
+"   int idx = get_global_id(0);                      \n"
+"                                                    \n"
+"   // Add the corresponding locations of            \n"
+"   // 'A' and 'B', and store the result in 'C'.     \n"
+"   C[idx] = A[idx] + B[idx];                        \n"
+"}                                                   \n"
+;
+
+typedef enum {false=0, true} bool;
+
+int main() {
+	// This code executes on the OpenCL host
+
+	// Host data
+	int *A = NULL;  // Input array
+	int *B = NULL;  // Input array
+	int *C = NULL;  // Output array
+
+	// Elements in each array
+	const int elements = 2048;
+
+	// Compute the size of the data
+	size_t datasize = sizeof(int)*elements;
+
+	// Allocate space for input/output data
+	A = (int*)malloc(datasize);
+	B = (int*)malloc(datasize);
+	C = (int*)malloc(datasize);
+	// Initialize the input data
+	for(int i = 0; i < elements; i++) {
+		A[i] = i;
+		B[i] = i;
+	}
+
+	// Use this to check the output of each API call
+	cl_int status;
+
+	//-----------------------------------------------------
+	// STEP 1: Discover and initialize the platforms
+	//-----------------------------------------------------
+
+	cl_uint numPlatforms = 0;
+	cl_platform_id *platforms = NULL;
+
+	// Use clGetPlatformIDs() to retrieve the number of platforms
+	status = clGetPlatformIDs(0, NULL, &numPlatforms);
+
+	// Allocate enough space for each platform
+	platforms =
+		(cl_platform_id*)malloc(
+				numPlatforms*sizeof(cl_platform_id));
+
+	// Fill in platforms with clGetPlatformIDs()
+	status = clGetPlatformIDs(numPlatforms, platforms,
+			NULL);
+
+	//-----------------------------------------------------
+	// STEP 2: Discover and initialize the devices
+	//-----------------------------------------------------
+
+	cl_uint numDevices = 0;
+	cl_device_id *devices = NULL;
+
+	// Use clGetDeviceIDs() to retrieve the number of
+	// devices present
+	status = clGetDeviceIDs(
+			platforms[0],
+			CL_DEVICE_TYPE_ALL,
+			0,
+			NULL,
+			&numDevices);
+
+	// Allocate enough space for each device
+	devices =
+		(cl_device_id*)malloc(
+				numDevices*sizeof(cl_device_id));
+
+	// Fill in devices with clGetDeviceIDs()
+	status = clGetDeviceIDs(
+			platforms[0],
+			CL_DEVICE_TYPE_ALL,
+			numDevices,
+			devices,
+			NULL);
+
+	//-----------------------------------------------------
+	// STEP 3: Create a context
+	//-----------------------------------------------------
+
+	cl_context context = NULL;
+
+	// Create a context using clCreateContext() and
+	// associate it with the devices
+	context = clCreateContext(
+			NULL,
+			numDevices,
+			devices,
+			NULL,
+			NULL,
+			&status);
+
+	//-----------------------------------------------------
+	// STEP 4: Create a command queue
+	//-----------------------------------------------------
+
+	cl_command_queue cmdQueue;
+
+	// Create a command queue using clCreateCommandQueue(),
+	// and associate it with the device you want to execute
+	// on
+	cmdQueue = clCreateCommandQueue(
+			context,
+			devices[0],
+			0,
+			&status);
+
+	//-----------------------------------------------------
+	// STEP 5: Create device buffers
+	//-----------------------------------------------------
+
+	cl_mem bufferA;  // Input array on the device
+	cl_mem bufferB;  // Input array on the device
+	cl_mem bufferC;  // Output array on the device
+
+	// Use clCreateBuffer() to create a buffer object (d_A)
+	// that will contain the data from the host array A
+	bufferA = clCreateBuffer(
+			context,
+			CL_MEM_READ_ONLY,
+			datasize,
+			NULL,
+			&status);
+
+	// Use clCreateBuffer() to create a buffer object (d_B)
+	// that will contain the data from the host array B
+	bufferB = clCreateBuffer(
+			context,
+			CL_MEM_READ_ONLY,
+			datasize,
+			NULL,
+			&status);
+
+	// Use clCreateBuffer() to create a buffer object (d_C)
+	// with enough space to hold the output data
+	bufferC = clCreateBuffer(
+			context,
+			CL_MEM_WRITE_ONLY,
+			datasize,
+			NULL,
+			&status);
+
+	//-----------------------------------------------------
+	// STEP 6: Write host data to device buffers
+	//-----------------------------------------------------
+
+	// Use clEnqueueWriteBuffer() to write input array A to
+	// the device buffer bufferA
+	status = clEnqueueWriteBuffer(
+			cmdQueue,
+			bufferA,
+			CL_FALSE,
+			0,
+			datasize,
+			A,
+			0,
+			NULL,
+			NULL);
+
+	// Use clEnqueueWriteBuffer() to write input array B to
+	// the device buffer bufferB
+	status = clEnqueueWriteBuffer(
+			cmdQueue,
+			bufferB,
+			CL_FALSE,
+			0,
+			datasize,
+			B,
+			0,
+			NULL,
+			NULL);
+
+	//-----------------------------------------------------
+	// STEP 7: Create and compile the program
+	//-----------------------------------------------------
+
+	// Create a program using clCreateProgramWithSource()
+	cl_program program = clCreateProgramWithSource(
+			context,
+			1,
+			(const char**)&programSource,
+			NULL,
+			&status);
+
+	// Build (compile) the program for the devices with
+	// clBuildProgram()
+	status = clBuildProgram(
+			program,
+			numDevices,
+			devices,
+			NULL,
+			NULL,
+			NULL);
+
+	//-----------------------------------------------------
+	// STEP 8: Create the kernel
+	//-----------------------------------------------------
+
+	cl_kernel kernel = NULL;
+
+	// Use clCreateKernel() to create a kernel from the
+	// vector addition function (named "vecadd")
+	kernel = clCreateKernel(program, "vecadd", &status);
+
+	//-----------------------------------------------------
+	// STEP 9: Set the kernel arguments
+	//-----------------------------------------------------
+
+	// Associate the input and output buffers with the
+	// kernel
+	// using clSetKernelArg()
+	status  = clSetKernelArg(
+			kernel,
+			0,
+			sizeof(cl_mem),
+			&bufferA);
+	status |= clSetKernelArg(
+			kernel,
+			1,
+			sizeof(cl_mem),
+			&bufferB);
+	status |= clSetKernelArg(
+			kernel,
+			2,
+			sizeof(cl_mem),
+			&bufferC);
+
+	//-----------------------------------------------------
+	// STEP 10: Configure the work-item structure
+	//-----------------------------------------------------
+
+	// Define an index space (global work size) of work items for
+	// execution. A workgroup size (local work size) is not required,
+	// but can be used.
+	size_t globalWorkSize[1];
+	// There are 'elements' work-items
+	globalWorkSize[0] = elements;
+
+	//-----------------------------------------------------
+	// STEP 11: Enqueue the kernel for execution
+	//-----------------------------------------------------
+
+	// Execute the kernel by using clEnqueueNDRangeKernel().
+	// 'globalWorkSize' is the 1D dimension of the work-items
+	status = clEnqueueNDRangeKernel(
+			cmdQueue,
+			kernel,
+			1,
+			NULL,
+			globalWorkSize,
+			NULL,
+			0,
+			NULL,
+			NULL);
+
+	//-----------------------------------------------------
+	// STEP 12: Read the output buffer back to the host
+	//-----------------------------------------------------
+
+	// Use clEnqueueReadBuffer() to read the OpenCL output
+	// buffer (bufferC)
+	// to the host output array (C)
+	clEnqueueReadBuffer(
+			cmdQueue,
+			bufferC,
+			CL_TRUE,
+			0,
+			datasize,
+			C,
+			0,
+			NULL,
+			NULL);
+
+	// Verify the output
+	bool result = true;
+	for(int i = 0; i < elements; i++) {
+		if(C[i] != i+i) {
+			result = false;
+			break;
+		}
+	}
+	if(result) {
+		printf("Output is correct\n");
+	} else {
+		printf("Output is incorrect\n");
+	}
+
+	//-----------------------------------------------------
+	// STEP 13: Release OpenCL resources
+	//-----------------------------------------------------
+
+	// Free OpenCL resources
+	clReleaseKernel(kernel);
+	clReleaseProgram(program);
+	clReleaseCommandQueue(cmdQueue);
+	clReleaseMemObject(bufferA);
+	clReleaseMemObject(bufferB);
+	clReleaseMemObject(bufferC);
+	clReleaseContext(context);
+
+	// Free host resources
+	free(A);
+	free(B);
+	free(C);
+	free(platforms);
+	free(devices);
+}
+
+// vim: ft=c ts=4 sw=4: