minimal_example.py

# coding=utf-8

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# ignore this (just for development without installation)
import sys
sys.path.append("..")
sys.path.append(".")

import torch
import torch_harmonics as harmonics

try:
    from tqdm import tqdm
except:
    tqdm = lambda x : x

# everything is awesome on GPUs
device = torch.device("cuda")

# create a batch with one sample and 21 channels
b, c, n_theta, n_lambda = 1, 21, 360, 720

# your layers to play with
forward_transform = harmonics.RealSHT(n_theta, n_lambda).to(device)
inverse_transform = harmonics.InverseRealSHT(n_theta, n_lambda).to(device)
forward_transform_equi = harmonics.RealSHT(n_theta, n_lambda, grid="equiangular").to(device)
inverse_transform_equi = harmonics.InverseRealSHT(n_theta, n_lambda, grid="equiangular").to(device)

signal_leggauss = inverse_transform(torch.randn(b, c, n_theta, n_theta+1, device=device, dtype=torch.complex128))
signal_equi = inverse_transform(torch.randn(b, c, n_theta, n_theta+1, device=device, dtype=torch.complex128))

# let's check the layers
for num_iters in [1, 8, 64, 512]:
    base = signal_leggauss
    for iteration in tqdm(range(num_iters)):
        base = inverse_transform(forward_transform(base))
    print("relative l2 error accumulation on the legendre-gauss grid: ",
          torch.mean(torch.norm(base-signal_leggauss, p='fro', dim=(-1,-2)) / torch.norm(signal_leggauss, p='fro', dim=(-1,-2)) ).item(),
          "after", num_iters, "iterations")

# let's check the equiangular layers
for num_iters in [1, 8, 64, 512]:
    base = signal_equi
    for iteration in tqdm(range(num_iters)):
        base = inverse_transform_equi(forward_transform_equi(base))
    print("relative l2 error accumulation with interpolation onto equiangular grid: ",
          torch.mean(torch.norm(base-signal_equi, p='fro', dim=(-1,-2)) / torch.norm(signal_equi, p='fro', dim=(-1,-2)) ).item(),
          "after", num_iters, "iterations")