added LPCNet torch implementation

Signed-off-by: Jan Buethe <jbuethe@amazon.de>

dnn/torch/lpcnet/utils/sparsification/common.py

@@ -0,0 +1,92 @@
+import torch
+
+def sparsify_matrix(matrix : torch.tensor, density : float, block_size : list[int, int], keep_diagonal : bool=False, return_mask : bool=False):
+    """ sparsifies matrix with specified block size
+
+        Parameters:
+        -----------
+        matrix : torch.tensor
+            matrix to sparsify
+        density : int
+            target density
+        block_size : [int, int]
+            block size dimensions
+        keep_diagonal : bool
+            If true, the diagonal will be kept. This option requires block_size[0] == block_size[1] and defaults to False
+    """
+
+    m, n   = matrix.shape
+    m1, n1 = block_size
+
+    if m % m1 or n % n1:
+        raise ValueError(f"block size {(m1, n1)} does not divide matrix size {(m, n)}")
+
+    # extract diagonal if keep_diagonal = True
+    if keep_diagonal:
+        if m != n:
+            raise ValueError("Attempting to sparsify non-square matrix with keep_diagonal=True")
+
+        to_spare = torch.diag(torch.diag(matrix))
+        matrix   = matrix - to_spare
+    else:
+        to_spare = torch.zeros_like(matrix)
+
+    # calculate energy in sub-blocks
+    x = torch.reshape(matrix, (m // m1, m1, n // n1, n1))
+    x = x ** 2
+    block_energies = torch.sum(torch.sum(x, dim=3), dim=1)
+
+    number_of_blocks = (m * n) // (m1 * n1)
+    number_of_survivors = round(number_of_blocks * density)
+
+    # masking threshold
+    if number_of_survivors == 0:
+        threshold = 0
+    else:
+        threshold = torch.sort(torch.flatten(block_energies)).values[-number_of_survivors]
+
+    # create mask
+    mask = torch.ones_like(block_energies)
+    mask[block_energies < threshold] = 0
+    mask = torch.repeat_interleave(mask, m1, dim=0)
+    mask = torch.repeat_interleave(mask, n1, dim=1)
+
+    # perform masking
+    masked_matrix = mask * matrix + to_spare
+
+    if return_mask:
+        return masked_matrix, mask
+    else:
+        return masked_matrix
+
+def calculate_gru_flops_per_step(gru, sparsification_dict=dict(), drop_input=False):
+    input_size = gru.input_size
+    hidden_size = gru.hidden_size
+    flops = 0
+
+    input_density = (
+        sparsification_dict.get('W_ir', [1])[0]
+        + sparsification_dict.get('W_in', [1])[0]
+        + sparsification_dict.get('W_iz', [1])[0]
+    ) / 3
+
+    recurrent_density = (
+        sparsification_dict.get('W_hr', [1])[0]
+        + sparsification_dict.get('W_hn', [1])[0]
+        + sparsification_dict.get('W_hz', [1])[0]
+    ) / 3
+
+    # input matrix vector multiplications
+    if not drop_input:
+        flops += 2 * 3 * input_size * hidden_size * input_density
+
+    # recurrent matrix vector multiplications
+    flops += 2 * 3 * hidden_size * hidden_size * recurrent_density
+
+    # biases
+    flops += 6 * hidden_size
+
+    # activations estimated by 10 flops per activation
+    flops += 30 * hidden_size
+
+    return flops