Add variable autoencoder from tch-rs examples

Changes

1 changed files (+94/-11)

• src/vae.rs
  • @@ -1,13 +1,96 @@
    - use tch::nn::{Module, OptimizerConfig}; - use tch::{kind, nn, Device, Tensor}; + /* Variational Auto-Encoder on MNIST. + The implementation is based on: + https://github.com/pytorch/examples/blob/master/vae/main.py + + The 4 following dataset files can be downloaded from http://yann.lecun.com/exdb/mnist/ + These files should be extracted in the 'data' directory. + train-images-idx3-ubyte.gz + train-labels-idx1-ubyte.gz + t10k-images-idx3-ubyte.gz + t10k-labels-idx1-ubyte.gz + */ + + use anyhow::Result; + use tch::{nn, nn::Module, nn::OptimizerConfig, Kind, Reduction, Tensor}; + + struct VAE { + fc1: nn::Linear, + fc21: nn::Linear, + fc22: nn::Linear, + fc3: nn::Linear, + fc4: nn::Linear, + } + + impl VAE { + fn new(vs: &nn::Path) -> Self { + VAE { + fc1: nn::linear(vs / "fc1", 784, 400, Default::default()), + fc21: nn::linear(vs / "fc21", 400, 20, Default::default()), + fc22: nn::linear(vs / "fc22", 400, 20, Default::default()), + fc3: nn::linear(vs / "fc3", 20, 400, Default::default()), + fc4: nn::linear(vs / "fc4", 400, 784, Default::default()), + } + } + + fn encode(&self, xs: &Tensor) -> (Tensor, Tensor) { + let h1 = xs.apply(&self.fc1).relu(); + (self.fc21.forward(&h1), self.fc22.forward(&h1)) + } + + fn decode(&self, zs: &Tensor) -> Tensor { + zs.apply(&self.fc3).relu().apply(&self.fc4).sigmoid() + } + + fn forward(&self, xs: &Tensor) -> (Tensor, Tensor, Tensor) { + let (mu, logvar) = self.encode(&xs.view([-1, 784])); + let std = (&logvar * 0.5).exp(); + let eps = std.randn_like(); + (self.decode(&(&mu + eps * std)), mu, logvar) + } + } + + // Reconstruction + KL divergence losses summed over all elements and batch dimension. + fn loss(recon_x: &Tensor, x: &Tensor, mu: &Tensor, logvar: &Tensor) -> Tensor { + let bce = recon_x.binary_cross_entropy::<Tensor>(&x.view([-1, 784]), None, Reduction::Sum); + // See Appendix B from VAE paper: + // Kingma and Welling. Auto-Encoding Variational Bayes. ICLR, 2014 + // https://arxiv.org/abs/1312.6114 + // 0.5 * sum(1 + log(sigma^2) - mu^2 - sigma^2) + let kld = -0.5 * (1i64 + logvar - mu.pow_tensor_scalar(2) - logvar.exp()).sum(Kind::Float); + bce + kld + } - pub fn vae(vs: &nn::Path) -> impl Module { - nn::seq() - .add(nn::linear(vs, 100, 50, Default::default())) - .add_fn(|xs| xs.relu()) - .add(nn::linear(vs, 50, 10, Default::default())) - .add_fn(|xs| xs.relu()) - .add(nn::linear(vs, 10, 50, Default::default())) - .add_fn(|xs| xs.relu()) - .add(nn::linear(vs, 50, 100, Default::default())) + // Generate a 2D matrix of images from a tensor with multiple images. + fn image_matrix(imgs: &Tensor, sz: i64) -> Result<Tensor> { + let imgs = (imgs * 256.).clamp(0., 255.).to_kind(Kind::Uint8); + let mut ys: Vec<Tensor> = vec![]; + for i in 0..sz { + ys.push(Tensor::cat(&(0..sz).map(|j| imgs.narrow(0, 4 * i + j, 1)).collect::<Vec<_>>(), 2)) + } + Ok(Tensor::cat(&ys, 3).squeeze_dim(0)) } + + pub fn main() -> Result<()> { + let device = tch::Device::cuda_if_available(); + let m = tch::vision::mnist::load_dir("data")?; + let vs = nn::VarStore::new(device); + let vae = VAE::new(&vs.root()); + let mut opt = nn::Adam::default().build(&vs, 1e-3)?; + for epoch in 1..21 { + let mut train_loss = 0f64; + let mut samples = 0f64; + for (bimages, _) in m.train_iter(128).shuffle().to_device(vs.device()) { + let (recon_batch, mu, logvar) = vae.forward(&bimages); + let loss = loss(&recon_batch, &bimages, &mu, &logvar); + opt.backward_step(&loss); + train_loss += f64::from(&loss); + samples += bimages.size()[0] as f64; + } + println!("Epoch: {}, loss: {}", epoch, train_loss / samples); + let s = Tensor::randn(&[64, 20], tch::kind::FLOAT_CPU).to(device); + let s = vae.decode(&s).to(tch::Device::Cpu).view([64, 1, 28, 28]); + tch::vision::image::save(&image_matrix(&s, 8)?, format!("s_{}.png", epoch))? + } + Ok(()) + } +