Add the gather op. (#219)

* Start adding gather.

* Gather cpu implementation + use in simple training.

* Add scatter_add for the gradient of gather.

* Simple cpu implementation of scatter_add.

* Use gather in the simple-training backprop.
This commit is contained in:
Laurent Mazare
2023-07-22 08:21:28 +02:00
committed by GitHub
parent 6eeea1b04e
commit 52c5d8c087
9 changed files with 315 additions and 14 deletions

View File

@ -17,10 +17,11 @@ fn log_softmax<D: candle::shape::Dim>(xs: &Tensor, d: D) -> candle::Result<Tenso
Ok(log_sm)
}
// TODO: Once the index_select backprop is efficient enough, switch to using this.
fn _nll_loss(inp: &Tensor, target: &Tensor) -> candle::Result<Tensor> {
let b_sz = target.shape().r1()?;
inp.index_select(target, 0)?.sum_all()? / b_sz as f64
fn nll_loss(inp: &Tensor, target: &Tensor) -> candle::Result<Tensor> {
let b_sz = target.dim(0)?;
inp.gather(target, 1)?
.sum_all()?
.affine(-1f64 / b_sz as f64, 0.)
}
pub fn main() -> Result<()> {
@ -32,12 +33,7 @@ pub fn main() -> Result<()> {
println!("test-labels: {:?}", m.test_labels.shape());
let train_labels = m.train_labels;
let train_images = m.train_images;
let train_labels = train_labels.to_vec1::<u8>()?;
let train_label_mask = train_labels
.iter()
.flat_map(|l| (0..LABELS).map(|i| f32::from(i == *l as usize)))
.collect::<Vec<_>>();
let train_label_mask = Tensor::from_vec(train_label_mask, (train_labels.len(), LABELS), &dev)?;
let train_labels = train_labels.to_dtype(DType::U32)?.unsqueeze(1)?;
let ws = Var::zeros((IMAGE_DIM, LABELS), DType::F32, &dev)?;
let bs = Var::zeros(LABELS, DType::F32, &dev)?;
let sgd = candle_nn::SGD::new(&[&ws, &bs], 1.0);
@ -46,9 +42,7 @@ pub fn main() -> Result<()> {
for epoch in 1..200 {
let logits = train_images.matmul(&ws)?.broadcast_add(&bs)?;
let log_sm = log_softmax(&logits, D::Minus1)?;
let loss = (&log_sm * &train_label_mask)?
.sum_all()?
.affine(-1f64 / train_images.dim(0)? as f64, 0f64)?;
let loss = nll_loss(&log_sm, &train_labels)?;
sgd.backward_step(&loss)?;
let test_logits = test_images.matmul(&ws)?.broadcast_add(&bs)?;
@ -63,7 +57,7 @@ pub fn main() -> Result<()> {
"{epoch:4} train loss: {:8.5} test acc: {:5.2}%",
loss.to_scalar::<f32>()?,
100. * test_accuracy
)
);
}
Ok(())
}