[docs] Redesign (#31757)

* toctree

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Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

* fix

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---------

Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>

* "to be not" -> "not to be" (#32636)

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* Update sam.md

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---------

Co-authored-by: Younes Belkada <49240599+younesbelkada@users.noreply.github.com>
Co-authored-by: Arthur <48595927+ArthurZucker@users.noreply.github.com>
Co-authored-by: Quentin Gallouédec <45557362+qgallouedec@users.noreply.github.com>
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@@ -1,4 +1,4 @@
<!--Copyright 2021 The HuggingFace Team. All rights reserved.
<!--Copyright 2024 The HuggingFace Team. All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
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@@ -14,55 +14,52 @@ rendered properly in your Markdown viewer.
-->
# Debugging
# Multi-GPU debugging
Training on multiple GPUs can be a tricky endeavor whether you're running into installation issues or communication problems between your GPUs. This debugging guide covers some issues you may run into and how to resolve them.
Distributed training can be tricky because you have to ensure you're using the correct CUDA version across your system. You may encounter inter-communication issues between GPUs, and there may be underflow or overflow problems in your model.
## DeepSpeed CUDA installation
This guide covers how to debug these issues, especially as it relates to DeepSpeed and PyTorch.
If you're using DeepSpeed, you've probably already installed it with the following command.
## DeepSpeed CUDA
DeepSpeed compiles CUDA C++ which can be a potential source of errors when building PyTorch extensions that require CUDA. These errors depend on how CUDA is installed on your system. This section focuses on PyTorch built with *CUDA 10.2*
```bash
pip install deepspeed
```
DeepSpeed compiles CUDA C++ code and it can be a potential source of errors when building PyTorch extensions that require CUDA. These errors depend on how CUDA is installed on your system, and this section focuses on PyTorch built with *CUDA 10.2*.
> [!TIP]
> For any other installation issues, please [open an issue](https://github.com/microsoft/DeepSpeed/issues) with the DeepSpeed team.
<Tip>
### Non-identical toolkits
For any other installation issues, please [open an issue](https://github.com/deepspeedai/DeepSpeed/issues) with the DeepSpeed team.
PyTorch comes with its own CUDA toolkit, but to use DeepSpeed with PyTorch, you need to have an identical version of CUDA installed system-wide. For example, if you installed PyTorch with `cudatoolkit==10.2` in your Python environment, then you'll also need to have CUDA 10.2 installed everywhere.
</Tip>
### Non-identical CUDA toolkits
PyTorch comes with its own CUDA toolkit, but to use DeepSpeed with PyTorch, you need to have an identical version of CUDA installed system-wide. For example, if you installed PyTorch with `cudatoolkit==10.2` in your Python environment, then you'll also need to have CUDA 10.2 installed system-wide. If you don't have CUDA installed system-wide, you should install it first.
The exact location may vary from system to system, but `usr/local/cuda-10.2` is the most common location on many Unix systems. When CUDA is correctly setup and added to your `PATH` environment variable, you can find the installation location with the following command:
The exact location can vary from system to system, but `usr/local/cuda-10.2` is the most common location on many Unix systems. When CUDA is correctly set up and added to your `PATH` environment variable, you can find the installation location with the following command.
```bash
which nvcc
```
### Multiple CUDA toolkits
### Multiple toolkits
You may also have more than one CUDA toolkit installed system-wide.
You may also have more than one CUDA toolkit installed on your system.
```bash
/usr/local/cuda-10.2
/usr/local/cuda-11.0
```
Typically, package installers set the paths to whatever the last version was installed. If the package build fails because it can't find the right CUDA version (despite it being installed system-wide already), then you need to configure the `PATH` and `LD_LIBRARY_PATH` environment variables to point to the correct path.
Typically, package installers set the paths to whatever the last version was installed. If the package build fails because it can't find the right CUDA version (despite it being installed already), then you need to configure the `PATH` and `LD_LIBRARY_PATH` environment variables to point to the correct path.
Take a look at the contents of these environment variables first:
Take a look at the contents of the following environment variables first.
```bash
echo $PATH
echo $LD_LIBRARY_PATH
```
`PATH` lists the locations of the executables and `LD_LIBRARY_PATH` lists where to look for shared libraries. Earlier entries are prioritized over later ones, and `:` is used to separate multiple entries. To tell the build program where to find the specific CUDA toolkit you want, insert the correct path to list first. This command prepends rather than overwrites the existing values.
`PATH` lists the locations of the executables and `LD_LIBRARY_PATH` lists where to look for shared libraries. Earlier entries are prioritized over later ones, and `:` is used to separate multiple entries. To find a specific CUDA toolkit, insert the correct path to list first. This command prepends rather than overwrites the existing values.
```bash
# adjust the version and full path if needed
@@ -70,23 +67,23 @@ export PATH=/usr/local/cuda-10.2/bin:$PATH
export LD_LIBRARY_PATH=/usr/local/cuda-10.2/lib64:$LD_LIBRARY_PATH
```
In addition, you should also check the directories you assign actually exist. The `lib64` sub-directory contains various CUDA `.so` objects (like `libcudart.so`) and while it is unlikely your system names them differently, you should check the actual names and change them accordingly.
In addition, you should also check that the assigned directories actually exist. The `lib64` sub-directory contains various CUDA `.so` objects (like `libcudart.so`), and while it is unlikely your system names them differently, you should check the actual names and change them accordingly.
### Older CUDA versions
### Older versions
Sometimes, older CUDA versions may refuse to build with newer compilers. For example, if you have `gcc-9` but CUDA wants `gcc-7`. Usually, installing the latest CUDA toolkit enables support for the newer compiler.
You could also install an older version of the compiler in addition to the one you're currently using (or it may already be installed but it's not used by default and the build system can't see it). To resolve this, you can create a symlink to give the build system visibility to the older compiler.
You could also install an older version of the compiler in addition to the one you're currently using (or it may already be installed but it's not used by default and the build system can't see it). To resolve this, create a symlink to give the build system visibility to the older compiler.
```bash
# adapt the path to your system
# adjust the path to your system
sudo ln -s /usr/bin/gcc-7 /usr/local/cuda-10.2/bin/gcc
sudo ln -s /usr/bin/g++-7 /usr/local/cuda-10.2/bin/g++
```
### Prebuild
If you're still having issues with installing DeepSpeed or if you're building DeepSpeed at run time, you can try to prebuild the DeepSpeed modules before installing them. To make a local build for DeepSpeed:
If you're still having issues with installing DeepSpeed or if you're building DeepSpeed at run time, try to prebuild the DeepSpeed modules before installing them. Run the commands below to make a local build for DeepSpeed.
```bash
git clone https://github.com/deepspeedai/DeepSpeed/
@@ -97,19 +94,16 @@ TORCH_CUDA_ARCH_LIST="8.6" DS_BUILD_CPU_ADAM=1 DS_BUILD_UTILS=1 pip install . \
--disable-pip-version-check 2>&1 | tee build.log
```
<Tip>
> [!TIP]
> Add the `DS_BUILD_AIO=1` parameter to the build command to use NVMe offload. Make sure you install the libaio-dev package across your system.
To use NVMe offload, add the `DS_BUILD_AIO=1` parameter to the build command and make sure you install the libaio-dev package system-wide.
</Tip>
Next, you'll have to specify your GPU's architecture by editing the `TORCH_CUDA_ARCH_LIST` variable (find a complete list of NVIDIA GPUs and their corresponding architectures on this [page](https://developer.nvidia.com/cuda-gpus)). To check the PyTorch version that corresponds to your architecture, run the following command:
Next, specify your GPUs architecture by editing the `TORCH_CUDA_ARCH_LIST` variable (find a complete list of NVIDIA GPUs and their corresponding architectures on this [page](https://developer.nvidia.com/cuda-gpus)). To check the PyTorch version that corresponds to your architecture, run the following command.
```bash
python -c "import torch; print(torch.cuda.get_arch_list())"
```
Find the architecture for a GPU with the following command:
Find the architecture for a GPU with the following command.
<hfoptions id="arch">
<hfoption id="same GPUs">
@@ -121,7 +115,7 @@ CUDA_VISIBLE_DEVICES=0 python -c "import torch; print(torch.cuda.get_device_capa
</hfoption>
<hfoption id="specific GPU">
To find the architecture for GPU `0`:
Run the following command to find the architecture for GPU `0`. The results will show a value for `major` and `minor`, which is your GPU architecture. The GPU architecture below is `8.6`.
```bash
CUDA_VISIBLE_DEVICES=0 python -c "import torch; \
@@ -129,8 +123,6 @@ print(torch.cuda.get_device_properties(torch.device('cuda')))
"_CudaDeviceProperties(name='GeForce RTX 3090', major=8, minor=6, total_memory=24268MB, multi_processor_count=82)"
```
This means your GPU architecture is `8.6`.
</hfoption>
</hfoptions>
@@ -138,7 +130,7 @@ If you get `8, 6`, then you can set `TORCH_CUDA_ARCH_LIST="8.6"`. For multiple G
It is also possible to not specify `TORCH_CUDA_ARCH_LIST` and the build program automatically queries the GPU architecture of the build. However, it may or may not match the actual GPU on the target machine which is why it is better to explicitly specify the correct architecture.
For training on multiple machines with the same setup, you'll need to make a binary wheel:
For training on multiple machines with the same setup, you'll need to make a binary wheel as shown below.
```bash
git clone https://github.com/deepspeedai/DeepSpeed/
@@ -148,88 +140,64 @@ TORCH_CUDA_ARCH_LIST="8.6" DS_BUILD_CPU_ADAM=1 DS_BUILD_UTILS=1 \
python setup.py build_ext -j8 bdist_wheel
```
This command generates a binary wheel that'll look something like `dist/deepspeed-0.3.13+8cd046f-cp38-cp38-linux_x86_64.whl`. Now you can install this wheel locally or on another machine.
This command generates a binary wheel that'll look something like `dist/deepspeed-0.3.13+8cd046f-cp38-cp38-linux_x86_64.whl`. Install this wheel locally or on another machine.
```bash
pip install deepspeed-0.3.13+8cd046f-cp38-cp38-linux_x86_64.whl
```
## Multi-GPU Network Issues Debug
## Communication
When training or inferencing with `DistributedDataParallel` and multiple GPU, if you run into issue of inter-communication between processes and/or nodes, you can use the following script to diagnose network issues.
Distributed training involves communication between processes and or nodes and this can be a potential source of errors.
Download the script below to diagnose network issues, and then run it to test GPU communication. The example command below tests how two GPUs communicate. Adjust the `--nproc_per_node` and `--nnodes` parameters to adapt it to your system.
```bash
wget https://raw.githubusercontent.com/huggingface/transformers/main/scripts/distributed/torch-distributed-gpu-test.py
```
For example to test how 2 GPUs interact do:
```bash
python -m torch.distributed.run --nproc_per_node 2 --nnodes 1 torch-distributed-gpu-test.py
```
If both processes can talk to each and allocate GPU memory each will print an OK status.
For more GPUs or nodes adjust the arguments in the script.
The script prints an `OK` status if both GPUs are able to communicate and allocate memory. Take a closer look at the diagnostic script for more details and a recipe for running it in a SLURM environment.
You will find a lot more details inside the diagnostics script and even a recipe to how you could run it in a SLURM environment.
An additional level of debug is to add `NCCL_DEBUG=INFO` environment variable as follows:
Add the `NCCL_DEBUG=INFO` environment variable to report more NCCL-related debugging information.
```bash
NCCL_DEBUG=INFO python -m torch.distributed.run --nproc_per_node 2 --nnodes 1 torch-distributed-gpu-test.py
```
This will dump a lot of NCCL-related debug information, which you can then search online if you find that some problems are reported. Or if you're not sure how to interpret the output you can share the log file in an Issue.
## Underflow and overflow detection
Underflow and overflow can occur when activations or weights are `inf`, `nan`, and when `loss=NaN`. This may indicate an underflow or overflow issue. To detect these issues, activate the `DebugUnderflowOverflow` module in [`TrainingArguments.debug`] or import and add the module to your own training loop or another trainer class.
<hfoptions id="overflow">
<hfoption id="Trainer">
## Underflow and Overflow Detection
```py
from transformers import TrainingArguments
<Tip>
This feature is currently available for PyTorch-only.
</Tip>
<Tip>
For multi-GPU training it requires DDP (`torch.distributed.launch`).
</Tip>
<Tip>
This feature can be used with any `nn.Module`-based model.
</Tip>
If you start getting `loss=NaN` or the model exhibits some other abnormal behavior due to `inf` or `nan` in
activations or weights one needs to discover where the first underflow or overflow happens and what led to it. Luckily
you can accomplish that easily by activating a special module that will do the detection automatically.
If you're using [`Trainer`], you just need to add:
```bash
--debug underflow_overflow
args = TrainingArguments(
debug="underflow_overflow",
...
)
```
to the normal command line arguments, or pass `debug="underflow_overflow"` when creating the
[`TrainingArguments`] object.
</hfoption>
<hfoption id="PyTorch training loop">
If you're using your own training loop or another Trainer you can accomplish the same with:
```python
```py
from transformers.debug_utils import DebugUnderflowOverflow
debug_overflow = DebugUnderflowOverflow(model)
```
[`~debug_utils.DebugUnderflowOverflow`] inserts hooks into the model that immediately after each
forward call will test input and output variables and also the corresponding module's weights. As soon as `inf` or
`nan` is detected in at least one element of the activations or weights, the program will assert and print a report
like this (this was caught with `google/mt5-small` under fp16 mixed precision):
</hfoption>
</hfoptions>
```
The [`~debug_utils.DebugUnderflowOverflow`] module inserts hooks into the model to test the input and output variables and the corresponding model weights after each forward call. If `inf` or `nan` is detected in at least one element of the activations or weights, the module prints a report like the one shown below.
The example below is for fp16 mixed precision training with [google/mt5-small](https://huggingface.co/google/mt5-small).
```shell
Detected inf/nan during batch_number=0
Last 21 forward frames:
abs min abs max metadata
@@ -269,48 +237,20 @@ abs min abs max metadata
0.00e+00 inf output
```
The example output has been trimmed in the middle for brevity.
At the start of the report, you can see which batch number the error occurred. In this case, it occurred on the first batch.
The second column shows the value of the absolute largest element, so if you have a closer look at the last few frames,
the inputs and outputs were in the range of `1e4`. So when this training was done under fp16 mixed precision the very
last step overflowed (since under `fp16` the largest number before `inf` is `64e3`). To avoid overflows under
`fp16` the activations must remain way below `1e4`, because `1e4 * 1e4 = 1e8` so any matrix multiplication with
large activations is going to lead to a numerical overflow condition.
Each frame describes the module it is reporting on. For example, the frame below inspected `encoder.block.2.layer.1.layer_norm`. This indicates the layer norm in the first layer of the second block of the encoder. The forward calls are to `T5LayerNorm`.
At the very start of the trace you can discover at which batch number the problem occurred (here `Detected inf/nan during batch_number=0` means the problem occurred on the first batch).
Each reported frame starts by declaring the fully qualified entry for the corresponding module this frame is reporting
for. If we look just at this frame:
```
```shell
encoder.block.2.layer.1.layer_norm T5LayerNorm
8.69e-02 4.18e-01 weight
2.65e-04 3.42e+03 input[0]
1.79e-06 4.65e+00 output
```
Here, `encoder.block.2.layer.1.layer_norm` indicates that it was a layer norm for the first layer, of the second
block of the encoder. And the specific calls of the `forward` is `T5LayerNorm`.
The last frame reports on the `Dropout.forward` function. It called the `dropout` attribute from inside the `DenseReluDense` class. You can observe that the overflow (`inf`) occurred in the first layer of the encoders second block in the first batch. The absolute largest input element was 6.27e+04.
Let's look at the last few frames of that report:
```
Detected inf/nan during batch_number=0
Last 21 forward frames:
abs min abs max metadata
[...]
encoder.block.2.layer.1.DenseReluDense.wi_0 Linear
2.17e-07 4.50e+00 weight
1.79e-06 4.65e+00 input[0]
2.68e-06 3.70e+01 output
encoder.block.2.layer.1.DenseReluDense.wi_1 Linear
8.08e-07 2.66e+01 weight
1.79e-06 4.65e+00 input[0]
1.27e-04 2.37e+02 output
encoder.block.2.layer.1.DenseReluDense.wo Linear
1.01e-06 6.44e+00 weight
0.00e+00 9.74e+03 input[0]
3.18e-04 6.27e+04 output
```shell
encoder.block.2.layer.1.DenseReluDense T5DenseGatedGeluDense
1.79e-06 4.65e+00 input[0]
3.18e-04 6.27e+04 output
@@ -319,22 +259,11 @@ abs min abs max metadata
0.00e+00 inf output
```
The last frame reports for `Dropout.forward` function with the first entry for the only input and the second for the
only output. You can see that it was called from an attribute `dropout` inside `DenseReluDense` class. We can see
that it happened during the first layer, of the 2nd block, during the very first batch. Finally, the absolute largest
input elements was `6.27e+04` and same for the output was `inf`.
The `T5DenseGatedGeluDense.forward` function output activations had an absolute maximum value of 6.27e+04 which is close to fp16s maximum limit of 6.4e+04. In the next step, `Dropout` renormalizes the weights, after zeroing some elements, which pushes the absolute maximum value to greater than 6.4e+04 resulting in an overflow.
You can see here, that `T5DenseGatedGeluDense.forward` resulted in output activations, whose absolute max value was
around 62.7K, which is very close to fp16's top limit of 64K. In the next frame we have `Dropout` which renormalizes
the weights, after it zeroed some of the elements, which pushes the absolute max value to more than 64K, and we get an
overflow (`inf`).
Now that you know where the error is happening, you can investigate the modeling code in [modeling_t5.py](https://github.com/huggingface/transformers/blob/main/src/transformers/models/t5/modeling_t5.py).
As you can see it's the previous frames that we need to look into when the numbers start going into very large for fp16
numbers.
Let's match the report to the code from `models/t5/modeling_t5.py`:
```python
```py
class T5DenseGatedGeluDense(nn.Module):
def __init__(self, config):
super().__init__()
@@ -353,29 +282,11 @@ class T5DenseGatedGeluDense(nn.Module):
return hidden_states
```
Now it's easy to see the `dropout` call, and all the previous calls as well.
Since the detection is happening in a forward hook, these reports are printed immediately after each `forward`
returns.
Going back to the full report, to act on it and to fix the problem, we need to go a few frames up where the numbers
started to go up and most likely switch to the `fp32` mode here, so that the numbers don't overflow when multiplied
or summed up. Of course, there might be other solutions. For example, we could turn off `amp` temporarily if it's
enabled, after moving the original `forward` into a helper wrapper, like so:
```python
def _forward(self, hidden_states):
hidden_gelu = self.gelu_act(self.wi_0(hidden_states))
hidden_linear = self.wi_1(hidden_states)
hidden_states = hidden_gelu * hidden_linear
hidden_states = self.dropout(hidden_states)
hidden_states = self.wo(hidden_states)
return hidden_states
One solution is to go back a few steps before the values started growing too large and switch to fp32 so the numbers don't overflow when multiplied or summed. Another potential solution is to temporarily disable mixed precision training (`amp`).
```py
import torch
def forward(self, hidden_states):
if torch.is_autocast_enabled():
with torch.cuda.amp.autocast(enabled=False):
@@ -384,14 +295,11 @@ def forward(self, hidden_states):
return self._forward(hidden_states)
```
Since the automatic detector only reports on inputs and outputs of full frames, once you know where to look, you may
want to analyse the intermediary stages of any specific `forward` function as well. In such a case you can use the
`detect_overflow` helper function to inject the detector where you want it, for example:
The report only returns inputs and outputs of full frames, so you may also want to analyze the intermediate values of any `forward` function as well. Add the `detect_overflow` function after the forward calls to track `inf` or `nan` values in the intermediate `forwarded_states`.
```python
```py
from debug_utils import detect_overflow
class T5LayerFF(nn.Module):
[...]
@@ -403,40 +311,25 @@ class T5LayerFF(nn.Module):
return hidden_states + self.dropout(forwarded_states)
```
You can see that we added 2 of these and now we track if `inf` or `nan` for `forwarded_states` was detected
somewhere in between.
Finally, you can configure the number of frames printed by [`~debug_utils.DebugUnderflowOverflow`].
Actually, the detector already reports these because each of the calls in the example above is a `nn.Module`, but
let's say if you had some local direct calculations this is how you'd do that.
Additionally, if you're instantiating the debugger in your own code, you can adjust the number of frames printed from
its default, e.g.:
```python
```py
from transformers.debug_utils import DebugUnderflowOverflow
debug_overflow = DebugUnderflowOverflow(model, max_frames_to_save=100)
```
### Specific batch absolute min and max value tracing
### Batch tracing
The same debugging class can be used for per-batch tracing with the underflow/overflow detection feature turned off.
[`~debug_utils.DebugUnderflowOverflow`] is able to trace the absolute minimum and maximum values in each batch with the underflow and overflow feature disabled. This is useful for identifying where errors are occurring in the model.
Let's say you want to watch the absolute min and max values for all the ingredients of each `forward` call of a given
batch, and only do that for batches 1 and 3. Then you instantiate this class as:
The example below shows how to trace the minimum and maximum values in batches 1 and 3 (batches are zero-indexd).
```python
```py
debug_overflow = DebugUnderflowOverflow(model, trace_batch_nums=[1, 3])
```
And now full batches 1 and 3 will be traced using the same format as the underflow/overflow detector does.
Batches are 0-indexed.
This is helpful if you know that the program starts misbehaving after a certain batch number, so you can fast-forward
right to that area. Here is a sample truncated output for such configuration:
```
```shell
*** Starting batch number=1 ***
abs min abs max metadata
shared Embedding
@@ -465,13 +358,10 @@ abs min abs max metadata
[...]
```
Here you will get a huge number of frames dumped - as many as there were forward calls in your model, so it may or may
not what you want, but sometimes it can be easier to use for debugging purposes than a normal debugger. For example, if
a problem starts happening at batch number 150. So you can dump traces for batches 149 and 150 and compare where
numbers started to diverge.
[`~debug_utils.DebugUnderflowOverflow`] reports on a large number of frames which is easier for debugging. Once you know where a problem is occurring, say batch 150, then you can focus the trace for batches 149 and 150 and compare where the numbers are diverging.
You can also specify the batch number after which to stop the training, with:
It is also possible to abort the trace after a certain batch number, for example, batch 3.
```python
```py
debug_overflow = DebugUnderflowOverflow(model, trace_batch_nums=[1, 3], abort_after_batch_num=3)
```