experimental: Add minimal rust backend.

.github/workflows/ci.yml

@@ -88,6 +88,10 @@ jobs:
               libgmp-dev \
               pandoc
 
+      - name: Install rust
+        run: |
+            curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
+
       # NOTE(brad): libunwind-dev is a broken dependency of libgoogle-glog-dev, itself
       # a dependency of ceres. Without this step on jammy, apt-get install libgoogle-glog-dev
       # would fail. If this step could be removed and still have the build succeed, it should.

symforce/codegen/backends/rust/README.rst

@@ -0,0 +1,3 @@
+***THIS MODULE IS EXPERIMENTAL***
+
+Backend for Rust. This currently only supports vector/matrices inputs and outputs, we do not have geo or cam types for Rust yet.

symforce/codegen/backends/rust/__init__.py

@@ -0,0 +1,12 @@
+# ----------------------------------------------------------------------------
+# SymForce - Copyright 2022, Skydio, Inc.
+# This source code is under the Apache 2.0 license found in the LICENSE file.
+# ----------------------------------------------------------------------------
+
+from pathlib import Path
+
+__doc__ = (Path(__file__).parent / "README.rst").read_text()
+
+from .rust_code_printer import RustCodePrinter
+from .rust_code_printer import ScalarType
+from .rust_config import RustConfig

symforce/codegen/backends/rust/rust_code_printer.py

@@ -0,0 +1,151 @@
+# ----------------------------------------------------------------------------
+# SymForce - Copyright 2022, Skydio, Inc.
+# This source code is under the Apache 2.0 license found in the LICENSE file.
+# ----------------------------------------------------------------------------
+
+from enum import Enum
+
+import sympy
+from sympy.core.singleton import S
+from sympy.core.numbers import Rational
+from sympy.codegen.ast import float32
+from sympy.codegen.ast import float64
+from sympy.codegen.ast import real
+from sympy.printing.rust import RustCodePrinter as SympyRustCodePrinter
+
+from symforce import typing as T
+
+
+class ScalarType(Enum):
+    FLOAT = float32
+    DOUBLE = float64
+
+
+class RustCodePrinter(SympyRustCodePrinter):
+    """
+    SymForce code printer for Rust. Based on the SymPy Rust printer.
+    """
+
+    def __init__(
+        self,
+        scalar_type: ScalarType,
+        settings: T.Optional[T.Dict[str, T.Any]] = None,
+        override_methods: T.Optional[T.Dict[sympy.Function, str]] = None,
+    ) -> None:
+        super().__init__(dict(settings or {}))
+
+        self.scalar_type = scalar_type.value
+        self.override_methods = override_methods or {}
+        for expr, name in self.override_methods.items():
+            self._set_override_methods(expr, name)
+
+    def _set_override_methods(self, expr: sympy.Function, name: str) -> None:
+        method_name = f"_print_{str(expr)}"
+
+        def _print_expr(expr: sympy.Expr) -> str:
+            expr_string = ", ".join(map(self._print, expr.args))
+            return f"{name}({expr_string})"
+
+        setattr(self, method_name, _print_expr)
+
+    def _print(self, expr: sympy.Expr, **kwargs):
+        # For whatever reason S.Zero is not a sympy.Integer, so we need to handle it separately
+        # by returning "0.0" instead of "0" to avoid compilation errors.
+        if expr == S.Zero:
+            return "0.0"
+        return super()._print(expr, **kwargs)
+
+    def _print_Integer(self, expr: sympy.Integer) -> T.Any:
+        """
+        Customizations:
+            * Cast all integers to either f32 or f64 because Rust does not have implicit casting
+            and needs to know the type of the literal at compile time. We assume that we are only
+            ever operating on floats in SymForce which should make this safe.
+        """
+        if self.scalar_type is float32:
+            return f"{expr.p}_f32"
+        if self.scalar_type is float64:
+            return f"{expr.p}_f64"
+        assert False, f"Scalar type {self.scalar_type} not supported"
+
+    def _print_Pow(self, expr):
+
+        if expr.exp.is_rational:
+            power = self._print_Rational(expr.exp)
+            func = "powf"
+            return f"{self._print(expr.base)}.{func}({power})"
+        else:
+            power = self._print(expr.exp)
+
+        if expr.exp.is_integer:
+            func = "powi"
+        else:
+            func = "powf"
+
+        return f"{expr.base}.{func}({power})"
+
+    def _print_ImaginaryUnit(self, expr: sympy.Expr) -> str:
+        """
+        Customizations:
+            * Print 1i instead of I
+            * Cast to Scalar, since the literal is of type std::complex<double>
+        """
+        return "Scalar(1i)"
+
+
+    def _print_Float(self, flt: sympy.Float) -> T.Any:
+        """
+        Customizations:
+            * Cast all literals to Scalar at compile time instead of using a suffix at codegen time
+        """
+        if self.scalar_type is float32:
+            return f"{super()._print_Float(flt)}_f32"
+        if self.scalar_type is float64:
+            return f"{super()._print_Float(flt)}_f64"
+
+        raise NotImplementedError(f"Scalar type {self.scalar_type} not supported")
+
+    def _print_Pi(self, expr, _type=False):
+        if self.scalar_type is float32:
+            return f"core::f32::consts::PI"
+        if self.scalar_type is float64:
+            return f"core::f64::consts::PI"
+
+    def _print_Max(self, expr: sympy.Max) -> str:
+        """
+        Customizations:
+            * The first argument calls the max method on the second argument.
+        """
+        return "{}.max({})".format(self._print(expr.args[0]), self._print(expr.args[1]))
+
+    def _print_Min(self, expr: sympy.Min) -> str:
+        """
+        Customizations:
+            * The first argument calls the min method on the second argument.
+        """
+        return "{}.min({})".format(self._print(expr.args[0]), self._print(expr.args[1]))
+
+    def _print_log(self, expr: sympy.log) -> str:
+        """
+        Customizations:
+        """
+        return "{}.ln()".format(self._print(expr.args[0]))
+
+
+    def _print_Rational(self, expr):
+        p, q = int(expr.p), int(expr.q)
+
+        float_suffix = None
+        if self.scalar_type is float32:
+            float_suffix = 'f32'
+        elif self.scalar_type is float64:
+            float_suffix = 'f64'
+
+        return f"({p}_{float_suffix}/{q}_{float_suffix})"
+
+
+    def _print_Exp1(self, expr, _type=False):
+        if self.scalar_type is float32:
+            return 'core::f32::consts::E'
+        elif self.scalar_type is float64:
+            return 'core::f64::consts::E'

symforce/codegen/backends/rust/rust_config.py

@@ -0,0 +1,60 @@
+# ----------------------------------------------------------------------------
+# SymForce - Copyright 2022, Skydio, Inc.
+# This source code is under the Apache 2.0 license found in the LICENSE file.
+# ----------------------------------------------------------------------------
+from dataclasses import dataclass
+from pathlib import Path
+
+import sympy
+from sympy.printing.codeprinter import CodePrinter
+
+from symforce import typing as T
+from symforce.codegen.backends.rust import rust_code_printer
+from symforce.codegen.codegen_config import CodegenConfig
+
+CURRENT_DIR = Path(__file__).parent
+
+
+@dataclass
+class RustConfig(CodegenConfig):
+    """
+    Code generation config for the Rust backend.
+
+    Args:
+        doc_comment_line_prefix: Prefix applied to each line in a docstring
+        line_length: Maximum allowed line length in docstrings; used for formatting docstrings.
+        scalar_type: The scalar type to use (float or double)
+    """
+
+    doc_comment_line_prefix: str = "///"
+    line_length: int = 100
+    scalar_type: rust_code_printer.ScalarType = rust_code_printer.ScalarType.FLOAT
+    use_eigen_types: bool = False
+
+    @classmethod
+    def backend_name(cls) -> str:
+        return "rust"
+
+    @classmethod
+    def template_dir(cls) -> Path:
+        return CURRENT_DIR / "templates"
+
+    def templates_to_render(self, generated_file_name: str) -> T.List[T.Tuple[str, str]]:
+        return [("function/FUNCTION.rs.jinja", f"{generated_file_name}.rs")]
+
+    def printer(self) -> CodePrinter:
+        kwargs: T.Mapping[str, T.Any] = {}
+        return rust_code_printer.RustCodePrinter(scalar_type=self.scalar_type, **kwargs)
+
+    def format_matrix_accessor(self, key: str, i: int, j: int, *, shape: T.Tuple[int, int]) -> str:
+        """
+        Format accessor for matrix types.
+
+        Assumes matrices are row-major.
+        """
+        RustConfig._assert_indices_in_bounds(i, j, shape)
+        if shape[1] == 1:
+            return f"{key}[{i}]"
+        if shape[0] == 1:
+            return f"{key}[{j}]"
+        return f"{key}[({i}, {j})]"

symforce/codegen/backends/rust/templates/function/FUNCTION.rs.jinja

@@ -0,0 +1,18 @@
+{# ----------------------------------------------------------------------------
+ # SymForce - Copyright 2022, Skydio, Inc.
+ # This source code is under the Apache 2.0 license found in the LICENSE file.
+ # ---------------------------------------------------------------------------- #}
+
+{%- import "../util/util.jinja" as util with context -%}
+
+
+pub mod {{ spec.namespace }} {
+
+{% if spec.docstring %}
+{{ util.print_docstring(spec.docstring) }}
+{% endif %}
+{{ util.function_declaration(spec) }} {
+    {{ util.expr_code(spec) }}
+}
+
+}  // mod {{ spec.namespace }}