Integrating SDFGs in Existing Programs

Compiling an SDFG creates a standalone dynamic library (.so, .dll, or .dylib) file that can be reused in existing programs, written in any language that supports calling C functions (or Foreign Function Interface, FFI). The library can be linked to the program at compile time, or loaded at runtime to Python using the CompiledSDFG class.

The file itself will be placed in the build folder of the SDFG, which by default is the .dacecache subfolder in the current working directory. This behavior is configurable through default_build_folder.


Calling the decorated DaCe function or SDFG object directly will compile the SDFG (if necessary) and execute it.

Using arrays with custom padding

When calling an SDFG from Python with standard NumPy or other array types, the strides are automatically set by the array programming library. However, if the SDFG uses custom padding, the array must be created with the correct dimensions and strides. DaCe provides a helper function to create such arrays: make_array_from_descriptor(). Example usage:

import dace

custom_desc =
    dace.float32, [10, 10],
    strides=[20, 1], start_offset=3)

def my_sdfg(A: custom_desc):

# Create an array with custom padding
a =
# Alternatively, sdfg.arrays['A'] could have been used as an argument

# A is a valid GPU (CuPy) array that can be used in the SDFG or outside of it
A[:] = 1

# Call the SDFG

Compiled SDFG objects


If performance of each call is not a concern (for example, if the SDFG runs for a long time), it is always preferable to call the SDFG object itself or the @dace function.

Compiled SDFG objects are usually returned from DaCe when compiling programs. You can also manually create one using the load_precompiled_sdfg() function for ease of use. The following example shows how to load a compiled SDFG directly:

import dace
from dace.codegen.compiled_sdfg import CompiledSDFG
from dace.sdfg.utils import load_precompiled_sdfg

# Load a compiled SDFG from a build folder
csdfg = load_precompiled_sdfg('.dacecache/my_sdfg')

# Load the compiled SDFG from an .so file directly (low-level API)
sdfg = dace.SDFG.from_file('my_sdfg.sdfg')
compiled_sdfg = CompiledSDFG(sdfg, '')

Internally, the CompiledSDFG class is a wrapper around ctypes that allows you to call the SDFG’s entry point function, perform basic type checking, and argument marshalling (i.e., array to pointer, Python callback to function pointer, etc.).

Since the compiled SDFG is a low-level interface, it is much faster to call than the Python interface. We show this behavior in the Benchmarking tutorial. However, it requires caution as opposed to calling the @dace.program or the SDFG object because:

  • Each array return value is represented internally as a single array (not reallocated every call) and will be reused across calls.

  • Less type checking is performed, so data may be reinterpreted if passed wrong.

  • The closure of the program (e.g., scalar fields in a class) will not be recomputed and thus may be stale.

Internal Structure and Functions

The build folder contains the compiled SDFG file (program.sdfg), the exact used configuration file for reproducibility, and several subfolders: src for source code, build for the linked library, include for an auto-generated header file that can be used to call the library, profiling for profiling, perf and data for instrumentation, map for source maps (used in debugging), and sample, which contains a short code sample that demonstrates how to invoke the library from C.

A compiled SDFG library contains three functions, which are named after the SDFG:

  • __dace_init_<SDFG name>: Initializes the SDFG, allocating all arrays and initializing all data descriptors. The function returns a handle to the state object, which is a struct containing all information that will persist between invocations of the SDFG. The other functions take this handle as their first argument. The arguments to this function are only the symbols used in the SDFG, ordered by name.

  • __dace_exit_<SDFG name>: Deallocates all arrays and frees all data descriptors in the given handle.

  • __program_<SDFG name>: The actual SDFG function, which takes the handle as its first argument, followed by the arguments to the SDFG, ordered by name, followed by the symbol arguments, also ordered by name.

The header file contains the function prototypes and the struct definition for the handle.

C/C++ and C ABI-Compatible Languages

The header file can be used to call the compiled SDFG from C, C++, or FORTRAN programs. The following example shows how to call a compiled SDFG from C:

#include "my_sdfg.h"

int main() {
    int M = 1, N = 20, K = 3;
    double *A = malloc(100 * N * sizeof(double));
    double *B = malloc(100 * M * sizeof(double));
    int i;

    // Initialize the SDFG (note that only the symbols are passed)
    my_sdfg_t handle = __dace_init_my_sdfg(K, M, N);

    // ...

    // Call the SDFG with arguments and symbols
    for (i = 0; i < 10; ++i)
        __program_my_sdfg(handle, A, B, K, M, N);

    // ...

    // Finalize the SDFG, freeing its resources

    return 0;