[src,build] Add minimal example to demonstrate pybind11 binding

src/makefiles/default_rules.mk

@@ -1,6 +1,7 @@
 
 SHELL := /bin/bash
 
+
 ifeq ($(KALDI_FLAVOR), dynamic)
   ifeq ($(shell uname), Darwin)
     ifdef LIBNAME
@@ -25,6 +26,13 @@ else
   XDEPENDS = $(ADDLIBS)
 endif
 
+ifeq ($(LIBFILE_EXTENSION),)
+else
+  # This will be reached if compiling in the pybind11 directory,
+  # which uses a special extension name for the library.
+  LIBFILE=$(LIBNAME)$(LIBFILE_EXTENSION)
+endif
+
 all: $(LIBFILE) $(BINFILES)
 
 $(LIBFILE): $(OBJFILES)

src/pybind/Makefile

@@ -0,0 +1,43 @@
+
+# make "all" the target.
+all:
+
+
+
+# Disable linking math libs because  not needed here.  Just for compilation speed.
+# no, it's now needed for context-fst-test.
+# MATHLIB = NONE
+
+EXTRA_CXXFLAGS = -Wno-sign-compare
+
+include ../kaldi.mk
+
+
+ifeq ($(KALDI_FLAVOR),static)
+  $(error You cannot build the pybind directory unless the build was dynamic; reconfigure with --shared option.)
+endif
+
+PYBIND_INCLUDES=$(shell python3 -m pybind11 --includes)
+CXXFLAGS += $(PYBIND_INCLUDES)
+PYBIND_EXTENSION=$(shell python3-config --extension-suffix)
+LIBFILE=kaldi-pybind
+LIBFILE_EXTENSION=$(PYBIND_EXTENSION)
+
+# pybind11 is heavily templated and generates code that is bloated before optimization.
+# -flto is link time optimization which apparently is important.
+CXXFLAGS += -O3 -flto
+LDFLAGS += -flto
+# TODO:
+
+ifeq ($(shell uname),Darwin)
+  LDFLAGS += -undefined dynamic_lookup
+endif
+
+OBJFILES = kaldi_pybind.o
+
+LIBNAME = kaldi_pybind
+
+# Note: the following will actually get turned into dynamic library names.
+ADDLIBS = ../lib/kaldi-util.so ../lib/kaldi-matrix.so ../lib/kaldi-base.so
+
+include ../makefiles/default_rules.mk

src/pybind/README.md

@@ -0,0 +1,14 @@
+This was tested as follows.  After configuring with --shared and making the rest of Kaldi,
+you can cd to here and do:
+```
+# make
+# python3
+>>> import kaldi_pybind as k
+>>> import numpy as np
+>>> a = k.FloatVector(10)
+>>> b = np.array(a, copy_data = False)
+>>> b[5:10] = 2.0
+>>> str(a)
+[ 0 0 0 0 0 2 2 2 2 2 ]
+
+```

src/pybind/kaldi_pybind.cc

@@ -0,0 +1,63 @@
+// pybind/kaldi_pybind.cc
+
+// Copyright 2019   Daniel Povey
+
+// See ../../COPYING for clarification regarding multiple authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
+// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
+// MERCHANTABLITY OR NON-INFRINGEMENT.
+// See the Apache 2 License for the specific language governing permissions and
+// limitations under the License.
+
+#include <pybind11/pybind11.h>
+#include <pybind11/stl.h>
+namespace py = pybind11;
+#include "matrix/kaldi-matrix.h"
+
+using namespace kaldi;
+
+PYBIND11_MODULE(kaldi_pybind, m) {
+  m.doc() = "pybind11 binding of some things from kaldi's src/matrix directory. "
+      "Source is in $(KALDI_ROOT)/src/pybind/matrix-lib.cc";
+
+  py::enum_<MatrixResizeType>(m, "MatrixResizeType", py::arithmetic(), "Matrix initialization policies")
+      .value("kSetZero", kSetZero, "Set to zero")
+      .value("kUndefined", kUndefined, "Leave undefined")
+      .value("kCopyData", kCopyData, "Copy any previously existing data")
+      .export_values();
+
+
+  py::class_<Vector<float> >(m, "FloatVector", pybind11::buffer_protocol())
+      .def_buffer([](const Vector<float> &v) -> pybind11::buffer_info {
+    return pybind11::buffer_info(
+        (void*)v.Data(),
+        sizeof(float),
+        pybind11::format_descriptor<float>::format(),
+        1, // num-axes
+        { v.Dim() },
+        { 4 }); // strides (in chars)
+        })
+      .def("Dim", &Vector<float>::Dim, "Return the dimension of the vector")
+      .def("__repr__",
+           [] (const Vector<float> &a) -> std::string {
+             std::ostringstream str;  a.Write(str, false); return str.str();
+           })
+      .def(py::init<const MatrixIndexT, MatrixResizeType>(),
+           py::arg("size"), py::arg("resize_type") = kSetZero);
+
+}
+
+
+
+
+
+
+