The original filenames as downloaded from http://yann.lecun.com/exdb/mnist/ don't contain dots in their filename but hyphens.

Here's a screenshot of the website:

Even in 2004 was the hyphen used for the filenames rather than dots. I suspect an application did not liked handling files without extensions...

This PR simply changes the expected file names to be loaded to contain hyphens.

I would like to fork and modify to then pull, but hesitant to do so without any license, please add a license, I would recommend MIT, but it is your choice!

This PR adds a download_mnist cargo feature (enabled by default) that exposes a new function to download the MNIST dataset and extract it automatically.

The function returns the directory where the files have been extracted so that it can be passed to functions loading the dataset.

This prevents having hardcoded paths in the example code.

Having a rust setup that autoformats the code using rustfmt makes it hard to hack on alumina since the two formats are quite different.

Rustfmt 1.0 RC came out two weeks ago (https://www.ncameron.org/blog/rustfmt-1-rc/) and is easily installed using rustup: rustup component add rustfmt-preview.

Then a simple cargo fmt will format the code base.

This changes a lot of files so I think the maintainer should be in a better position to do this.

Would you consider doing so?

Thank you!

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Error(SubgraphInsufficientInputsForOutputs(["prediction_loss_gradient"]), State { next_error: None, backtrace: Some(stack backtrace:
   0:     0x55d11fc81d54 - backtrace::backtrace::libunwind::trace
                        at /home/g/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.4/src/backtrace/libunwind.rs:53
                         - backtrace::backtrace::trace<closure>
                        at /home/g/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.4/src/backtrace/mod.rs:42
   1:     0x55d11fc7bc2c - backtrace::capture::{{impl}}::new_unresolved
                        at /home/g/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.4/src/capture.rs:88
   2:     0x55d11fc7bb7e - backtrace::capture::{{impl}}::new
                        at /home/g/.cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.4/src/capture.rs:63
   3:     0x55d11fc79406 - error_chain::make_backtrace
                        at /home/g/.cargo/registry/src/github.com-1ecc6299db9ec823/error-chain-0.11.0/src/lib.rs:616
   4:     0x55d11fc7946f - error_chain::{{impl}}::default
                        at /home/g/.cargo/registry/src/github.com-1ecc6299db9ec823/error-chain-0.11.0/src/lib.rs:710
   5:     0x55d11fc2ab91 - alumina::graph::{{impl}}::from_kind
                        at /home/g/Desktop/learned-index/<impl_error_chain_processed macros>:53
   6:     0x55d11fc2ae7c - alumina::graph::{{impl}}::from
                        at /home/g/.cargo/git/checkouts/alumina-6fbb489aa505e418/7c1b79e/src/graph.rs:16
   7:     0x55d11fc131fc - core::convert::{{impl}}::into<alumina::graph::ErrorKind,alumina::graph::Error>
                        at /checkout/src/libcore/convert.rs:415
   8:     0x55d11fc233a7 - alumina::graph::find_pass_order
                        at /home/g/.cargo/git/checkouts/alumina-6fbb489aa505e418/7c1b79e/src/graph.rs:1059
   9:     0x55d11fc1faad - alumina::graph::{{impl}}::new
                        at /home/g/.cargo/git/checkouts/alumina-6fbb489aa505e418/7c1b79e/src/graph.rs:730
  10:     0x55d11fc1693b - alumina::graph::{{impl}}::subgraph
                        at /home/g/.cargo/git/checkouts/alumina-6fbb489aa505e418/7c1b79e/src/graph.rs:194
  11:     0x55d11fc16d73 - alumina::graph::{{impl}}::default_subgraph
                        at /home/g/.cargo/git/checkouts/alumina-6fbb489aa505e418/7c1b79e/src/graph.rs:210
  12:     0x55d11fb08dd2 - alumina::opt::adam::{{impl}}::new
                        at /home/g/.cargo/git/checkouts/alumina-6fbb489aa505e418/7c1b79e/src/opt/adam.rs:38
  13:     0x55d11fa307bc - learned_index::nn::learn_test
                        at src/lib/nn.rs:40
  14:     0x55d11fa1f4d6 - learned_btree::main
                        at src/bin/btree/main.rs:13
  15:     0x55d11fd349ce - panic_unwind::__rust_maybe_catch_panic
                        at /checkout/src/libpanic_unwind/lib.rs:101
  16:     0x55d11fd20a73 - std::panic::catch_unwind<closure,()>
                        at /checkout/src/libstd/panicking.rs:459
                         - std::rt::lang_start
                        at /checkout/src/libstd/rt.rs:58
  17:     0x55d11fa1f51d - main
  18:     0x7f8ee148382f - __libc_start_main
  19:     0x55d11fa1be68 - _start
  20:                0x0 - <unknown>) })', /checkout/src/libcore/result.rs:916:4
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at /checkout/src/libstd/sys_common/backtrace.rs:68
             at /checkout/src/libstd/sys_common/backtrace.rs:57
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:397
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:577
   5: std::panicking::begin_panic
             at /checkout/src/libstd/panicking.rs:538
   6: std::panicking::begin_panic_fmt
             at /checkout/src/libstd/panicking.rs:522
   7: rust_begin_unwind
             at /checkout/src/libstd/panicking.rs:498
   8: core::panicking::panic_fmt
             at /checkout/src/libcore/panicking.rs:71
   9: core::result::unwrap_failed
             at /checkout/src/libcore/macros.rs:23
  10: <core::result::Result<T, E>>::unwrap
             at /checkout/src/libcore/result.rs:782
  11: learned_btree::main
             at src/bin/btree/main.rs:13
  12: __rust_maybe_catch_panic
             at /checkout/src/libpanic_unwind/lib.rs:101
  13: std::rt::lang_start
             at /checkout/src/libstd/panicking.rs:459
             at /checkout/src/libstd/rt.rs:58
  14: main
  15: __libc_start_main
  16: _start

I am testing out this framework. So currently I am modifying the MNIST example, changing the loss function to MSE and getting the error above.

/// A common mnist network with two hidden layers of 800 units and tanh activation functions
#[allow(unused)]
fn mnist_tanh_800(regularise: f32) -> Result<GraphDef> {
    let mut g = GraphDef::new();

    let input = g.new_node(shape![Unknown, 1], "input", tag![])?;
    let labels = g.new_node(shape![Unknown, 1], "labels", tag![])?;

    let layer1 = g.new_node(shape![Unknown, 10], "layer1", tag![])?;
    let layer1_activ = g.new_node(shape![Unknown, 10], "layer1_activ", tag![])?;

    let layer2 = g.new_node(shape![Unknown, 10], "layer2", tag![])?;
    let layer2_activ = g.new_node(shape![Unknown, 10], "layer2_activ", tag![])?;

    let prediction = g.new_node(shape![Unknown, 1], "prediction", tag![])?;
    let softmax = g.new_node(shape![Unknown, 1], "softmax", tag![])?;

    let prediction_loss = g.new_node(shape![Unknown], "prediction_loss", tag![])?;

    g.new_op(Linear::new(&input, &layer1).init(Linear::msra(1.0)), tag![])?;
    g.new_op(Bias::new(&layer1), tag![])?;
    g.new_op(Tanh::new(&layer1, &layer1_activ), tag![])?;

    g.new_op(Linear::new(&layer1_activ, &layer2).init(Linear::msra(1.0)), tag![])?;
    g.new_op(Bias::new(&layer2), tag![])?;
    g.new_op(Tanh::new(&layer2, &layer2_activ), tag![])?;

    g.new_op(Linear::new(&layer2_activ, &prediction).init(Linear::msra(1.0)), tag![])?;
    g.new_op(Softmax::new(&prediction, &softmax), tag![])?;
    g.new_op(CrossEntropy::new(&softmax, &labels), tag![])?;

    g.new_op(Mse::new(&prediction, &labels).output(&prediction_loss), tag![])?;

    Ok(g)
}