Add ConvNeXt model. (#1604)

candle-transformers/src/models/convnext.rs

@@ -0,0 +1,201 @@
+//! ConvNeXt implementation.
+//!
+//! See "A ConvNet for the 2020s" Liu et al. 2022
+//! <https://arxiv.org/abs/2201.03545>
+
+//! Original code: https://github.com/facebookresearch/ConvNeXt/
+//! timm: https://github.com/huggingface/pytorch-image-models/blob/main/timm/models/convnext.py
+
+use candle::{Result, D};
+use candle_nn::{conv2d, layer_norm, linear, Conv2dConfig, Func, VarBuilder};
+
+#[derive(Clone)]
+pub struct Config {
+    blocks: [usize; 4],
+    channels: [usize; 4],
+}
+
+impl Config {
+    pub fn tiny() -> Self {
+        Self {
+            blocks: [3, 3, 9, 3],
+            channels: [96, 192, 384, 768],
+        }
+    }
+    pub fn small() -> Self {
+        Self {
+            blocks: [3, 3, 27, 3],
+            channels: [96, 192, 384, 768],
+        }
+    }
+    pub fn base() -> Self {
+        Self {
+            blocks: [3, 3, 27, 3],
+            channels: [128, 256, 512, 1024],
+        }
+    }
+    pub fn large() -> Self {
+        Self {
+            blocks: [3, 3, 27, 3],
+            channels: [192, 384, 768, 1536],
+        }
+    }
+
+    pub fn xlarge() -> Self {
+        Self {
+            blocks: [3, 3, 27, 3],
+            channels: [256, 512, 1024, 2048],
+        }
+    }
+}
+
+// Initial downsampling via a patchify layer.
+fn convnext_stem(out_channels: usize, vb: VarBuilder) -> Result<Func<'static>> {
+    let conv2d_cfg = Conv2dConfig {
+        stride: 4,
+        ..Default::default()
+    };
+    let patchify = conv2d(3, out_channels, 4, conv2d_cfg, vb.pp(0))?;
+    let norm = layer_norm(out_channels, 1e-6, vb.pp(1))?;
+    Ok(Func::new(move |xs| {
+        // The layer norm works with channels-last format.
+        let xs = xs
+            .apply(&patchify)?
+            .permute((0, 2, 3, 1))?
+            .apply(&norm)?
+            .permute((0, 3, 1, 2))?;
+        Ok(xs)
+    }))
+}
+
+// Downsampling applied after the stages.
+fn convnext_downsample(dim: usize, vb: VarBuilder) -> Result<Func<'static>> {
+    let conv2d_cfg = Conv2dConfig {
+        stride: 2,
+        ..Default::default()
+    };
+    let norm = layer_norm(dim / 2, 1e-5, vb.pp(0))?;
+    let conv = conv2d(dim / 2, dim, 2, conv2d_cfg, vb.pp(1))?;
+    Ok(Func::new(move |xs| {
+        let xs = xs
+            .permute((0, 2, 3, 1))?
+            .apply(&norm)?
+            .permute((0, 3, 1, 2))?
+            .apply(&conv)?;
+        Ok(xs)
+    }))
+}
+
+// MLP equivalent of pointwise convolutions.
+fn convnext_mlp(dim: usize, vb: VarBuilder) -> Result<Func<'static>> {
+    let fc1 = linear(dim, 4 * dim, vb.pp("fc1"))?;
+    let fc2 = linear(4 * dim, dim, vb.pp("fc2"))?;
+
+    Ok(Func::new(move |xs| {
+        let xs = xs.apply(&fc1)?.gelu_erf()?.apply(&fc2)?;
+        Ok(xs)
+    }))
+}
+
+// A block consisting of a depthwise convolution, a MLP and layer scaling.
+fn convnext_block(dim: usize, vb: VarBuilder) -> Result<Func<'static>> {
+    let conv2d_cfg = Conv2dConfig {
+        groups: dim,
+        padding: 3,
+        ..Default::default()
+    };
+
+    let conv_dw = conv2d(dim, dim, 7, conv2d_cfg, vb.pp("conv_dw"))?;
+
+    let gamma = vb.get(dim, "gamma")?;
+    let mlp = convnext_mlp(dim, vb.pp("mlp"))?;
+    let norm = layer_norm(dim, 1e-6, vb.pp("norm"))?;
+
+    Ok(Func::new(move |xs| {
+        let residual = xs;
+        let xs = xs
+            .apply(&conv_dw)?
+            .permute((0, 2, 3, 1))?
+            .apply(&norm)?
+            .apply(&mlp)?
+            .broadcast_mul(&gamma)?
+            .permute((0, 3, 1, 2))?;
+
+        xs + residual
+    }))
+}
+
+// Each stage contains blocks and a downsampling layer for the previous stage.
+fn convnext_stage(cfg: &Config, stage_idx: usize, vb: VarBuilder) -> Result<Func<'static>> {
+    let nblocks = cfg.blocks[stage_idx];
+    let mut blocks = Vec::with_capacity(nblocks);
+
+    let dim = cfg.channels[stage_idx];
+
+    if stage_idx > 0 {
+        blocks.push(convnext_downsample(dim, vb.pp("downsample"))?);
+    }
+
+    for block_idx in 0..nblocks {
+        blocks.push(convnext_block(dim, vb.pp(format!("blocks.{block_idx}")))?);
+    }
+
+    Ok(Func::new(move |xs| {
+        let mut xs = xs.clone();
+        for block in blocks.iter() {
+            xs = xs.apply(block)?
+        }
+        Ok(xs)
+    }))
+}
+
+fn convnext_head(outputs: usize, nclasses: usize, vb: VarBuilder) -> Result<Func<'static>> {
+    let norm = layer_norm(outputs, 1e-6, vb.pp("norm"))?;
+    let linear = linear(outputs, nclasses, vb.pp("fc"))?;
+    Ok(Func::new(move |xs| xs.apply(&norm)?.apply(&linear)))
+}
+
+// Build a convnext model for a given configuration.
+fn convnext_model(
+    config: &Config,
+    nclasses: Option<usize>,
+    vb: VarBuilder,
+) -> Result<Func<'static>> {
+    let head = match nclasses {
+        None => None,
+        Some(nclasses) => {
+            let head = convnext_head(config.channels[3], nclasses, vb.pp("head"))?;
+            Some(head)
+        }
+    };
+
+    let stem = convnext_stem(config.channels[0], vb.pp("stem"))?;
+    let vb = vb.pp("stages");
+    let stage1 = convnext_stage(config, 0, vb.pp(0))?;
+    let stage2 = convnext_stage(config, 1, vb.pp(1))?;
+    let stage3 = convnext_stage(config, 2, vb.pp(2))?;
+    let stage4 = convnext_stage(config, 3, vb.pp(3))?;
+
+    Ok(Func::new(move |xs| {
+        let xs = xs
+            .apply(&stem)?
+            .apply(&stage1)?
+            .apply(&stage2)?
+            .apply(&stage3)?
+            .apply(&stage4)?
+            .mean(D::Minus2)?
+            .mean(D::Minus1)?;
+        match &head {
+            None => Ok(xs),
+            Some(head) => xs.apply(head),
+        }
+    }))
+}
+
+pub fn convnext(cfg: &Config, nclasses: usize, vb: VarBuilder) -> Result<Func<'static>> {
+    convnext_model(cfg, Some(nclasses), vb)
+}
+
+pub fn convnext_no_final_layer(cfg: &Config, vb: VarBuilder) -> Result<Func<'static>> {
+    convnext_model(cfg, None, vb)
+}

candle-transformers/src/models/mod.rs

@@ -3,6 +3,7 @@ pub mod bigcode;
 pub mod blip;
 pub mod blip_text;
 pub mod convmixer;
+pub mod convnext;
 pub mod dinov2;
 pub mod distilbert;
 pub mod efficientnet;