COMPMID-2466: Improved ConvLayer documentation.

Added two tables in NEConvolutionLayer and CLConvolutionLayer
showing ACL's criteria to choose the different algorithms.

Change-Id: Ie6e44e72381ab8232c050688c86d746eb8d2fb36
Signed-off-by: Pablo Tello <pablo.tello@arm.com>
Reviewed-on: https://review.mlplatform.org/c/1577
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
diff --git a/arm_compute/runtime/CL/functions/CLConvolutionLayer.h b/arm_compute/runtime/CL/functions/CLConvolutionLayer.h
index 96f69f2..04ce1cf 100644
--- a/arm_compute/runtime/CL/functions/CLConvolutionLayer.h
+++ b/arm_compute/runtime/CL/functions/CLConvolutionLayer.h
@@ -41,6 +41,32 @@
  * -# @ref CLWinogradConvolutionLayer
  * -# @ref CLDirectConvolutionLayer
  * -# @ref CLFFTConvolutionLayer
+ *
+ * The function selects one of the algorithms mentioned above based on:
+ *      - The size of the kernel
+ *      - Number of input/output feature maps
+ *      - Amount of memory needed
+ *
+ * Generally GEMM-based convolution is executed when neither Winograd nor FFT nor Direct convolution can be performed.
+ *
+ * FP32 Algorithm| Filter Size                                                 |   Input/Output feature maps               |
+ * --------------|-------------------------------------------------------------|-------------------------------------------|
+ * Winograd      | 3x3 1x3 3x1 5x1 1x5 5x5(fast maths) 7x1 1x7                 |  Input channels is greater than 3         |
+ * FFT           | Squared kernels and greater than 9x9                        |  Input feature maps > Output feature maps |
+ * DirectConv    | 9x9                                                         |                                           |
+ * GEMM          | Any size                                                    |                                           |
+ *
+ * Winograd 5x5 requires fast maths enabled.
+ *
+ * FP16 Algorithm| Filter Size                |   Input/Output feature maps               |
+ * --------------|----------------------------|-------------------------------------------|
+ * Winograd      | 3x3 1x3 3x1 5x1 1x5 5x5    |  Input channels is greater than 3         |
+ * FFT           | Not supported              |                                           |
+ * DirectConv    | 9x9                        |                                           |
+ * GEMM          | Any size                   |                                           |
+ *
+ * Winograd FP16 requires fast maths enabled.
+ *
  */
 class CLConvolutionLayer : public IFunction
 {