cpu

func (*CPUBackend) Add ¶

func (cpu *CPUBackend) Add(a, b *tensor.RawTensor) *tensor.RawTensor

Add performs element-wise addition with NumPy-style broadcasting.

func (*CPUBackend) Conv2D ¶

func (cpu *CPUBackend) Conv2D(input, kernel *tensor.RawTensor, stride, padding int) *tensor.RawTensor

Conv2D performs 2D convolution using im2col algorithm.

Input shape: [batch, in_channels, height, width] Kernel shape: [out_channels, in_channels, kernel_h, kernel_w] Output shape: [batch, out_channels, out_h, out_w]

Parameters:

• input: Input tensor [N, C_in, H, W]
• kernel: Convolution kernel [C_out, C_in, K_h, K_w]
• stride: Stride for convolution (default: 1)
• padding: Padding to apply (default: 0)

Algorithm: Im2col

1. Transform input patches into columns (im2col)
2. Reshape kernel into matrix
3. Perform matrix multiplication
4. Reshape output to [N, C_out, H_out, W_out]

Im2col is efficient because:

• Converts convolution to matmul (highly optimized)
• Cache-friendly memory access
• Reuses existing matmul code

Reference: "High Performance Convolutional Neural Networks for Document Processing" (Chellapilla et al., 2006).

func (*CPUBackend) Device ¶

func (cpu *CPUBackend) Device() tensor.Device

Device returns the compute device.

func (*CPUBackend) Div ¶

func (cpu *CPUBackend) Div(a, b *tensor.RawTensor) *tensor.RawTensor

Div performs element-wise division with broadcasting.

func (*CPUBackend) MatMul ¶

func (cpu *CPUBackend) MatMul(a, b *tensor.RawTensor) *tensor.RawTensor

MatMul performs matrix multiplication. For 2D tensors: (M, K) @ (K, N) -> (M, N) Uses naive O(n³) implementation for Phase 1. TODO: Integrate with gonum/blas for better performance in Phase 2.

func (*CPUBackend) MaxPool2D ¶

func (cpu *CPUBackend) MaxPool2D(input *tensor.RawTensor, kernelSize, stride int) *tensor.RawTensor

MaxPool2D performs 2D max pooling.

Max pooling reduces spatial dimensions by taking the maximum value in each pooling window. Unlike Conv2D, MaxPool2D has no learnable parameters.

Input shape: [batch, channels, height, width] Output shape: [batch, channels, out_height, out_width]

Where:

out_height = (height - kernelSize) / stride + 1
out_width = (width - kernelSize) / stride + 1

Algorithm:

1. For each batch and channel
2. Slide kernelSize x kernelSize window with given stride
3. Take maximum value in each window
4. Output max value

Example (2x2 pool, stride=2):

Input: [[1,2,3,4],    Output: [[4,6],
        [5,6,7,8],             [12,14]]
        [9,10,11,12],
        [13,14,15,16]]

func (*CPUBackend) Mul ¶

func (cpu *CPUBackend) Mul(a, b *tensor.RawTensor) *tensor.RawTensor

Mul performs element-wise multiplication with broadcasting.

func (*CPUBackend) Name ¶

func (cpu *CPUBackend) Name() string

Name returns the backend name.

func (*CPUBackend) ReLU ¶ added in v0.2.0

func (cpu *CPUBackend) ReLU(x *tensor.RawTensor) *tensor.RawTensor

ReLU applies ReLU activation: max(0, x).

func (*CPUBackend) Reshape ¶

func (cpu *CPUBackend) Reshape(t *tensor.RawTensor, newShape tensor.Shape) *tensor.RawTensor

Reshape returns a tensor with the same data but different shape.

func (*CPUBackend) Softmax ¶ added in v0.2.0

func (cpu *CPUBackend) Softmax(x *tensor.RawTensor) *tensor.RawTensor

Softmax applies softmax along the last dimension. Expects 2D input [batch_size, num_classes].

func (*CPUBackend) Sub ¶

func (cpu *CPUBackend) Sub(a, b *tensor.RawTensor) *tensor.RawTensor

Sub performs element-wise subtraction with broadcasting.

func (*CPUBackend) Transpose ¶

func (cpu *CPUBackend) Transpose(t *tensor.RawTensor, axes ...int) *tensor.RawTensor

Transpose transposes the tensor by permuting its dimensions.