using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace NumSharp.Core.Extensions

{

public static partial class NDArrayExtensions

{

public static NDArray<double> AMin(this NDArray<double> np, int? axis = null)

{

NDArray<double> res = new NDArray<double>();

if (axis == null)

{

res.Data = new double[1] { np.Data.Min() };

res.Shape = new Shape(new int[] { 1 });

}

else

{

if (axis < 0 || axis >= np.Shape.Length)

throw new Exception("Invalid input: axis");

int[] resShapes = new int[np.Shape.Shapes.Count - 1];

int index = 0; //index for result shape set

//axis departs the shape into three parts: prev, cur and post. They are all product of shapes

int prev = 1;

int cur = 1;

int post = 1;

int size = 1; //total number of the elements for result

//Calculate new Shape

for (int i = 0; i < np.Shape.Shapes.Count; i++)

{

if (i == axis)

cur = np.Shape.Shapes[i];

else

{

resShapes[index++] = np.Shape.Shapes[i];

size *= np.Shape.Shapes[i];

if (i < axis)

prev *= np.Shape.Shapes[i];

else

post *= np.Shape.Shapes[i];

}

}

res.Shape = new Shape(resShapes);

//Fill in data

index = 0; //index for result data set

int sameSetOffset = np.Shape.DimOffset[axis.Value];

int increments = cur * post;

res.Data = new double[size];

int start = 0;

double min = 0;

for (int i = 0; i < np.Size; i += increments)

{

for (int j = i; j < i + post; j++)

{

start = j;

min = np.Data[start];

for (int k = 0; k < cur; k++)

{

min = Math.Min(min, np.Data[start]);

start += sameSetOffset;

}

res.Data[index++] = min;

}

}

}

return res;

}

}

}