Merge pull request #99 from bluescarni/pr/neg

Implement unary negation.

CMakeLists.txt

@@ -191,6 +191,7 @@ set(HEYOKA_SRC_FILES
     "${CMAKE_CURRENT_SOURCE_DIR}/src/math/acosh.cpp"
     "${CMAKE_CURRENT_SOURCE_DIR}/src/math/atanh.cpp"
     "${CMAKE_CURRENT_SOURCE_DIR}/src/math/erf.cpp"
+    "${CMAKE_CURRENT_SOURCE_DIR}/src/math/neg.cpp"
     "${CMAKE_CURRENT_SOURCE_DIR}/src/detail/string_conv.cpp"
     "${CMAKE_CURRENT_SOURCE_DIR}/src/detail/math_wrappers.cpp"
     "${CMAKE_CURRENT_SOURCE_DIR}/src/detail/llvm_helpers.cpp"

doc/changelog.rst

@@ -7,6 +7,13 @@ Changelog
 New
 ~~~
 
+- Introduce a dedicated negation operator in the
+  expression system
+  (`#99 <https://github.com/bluescarni/heyoka/pull/99>`__).
+- Implement various new automatic simplifications
+  in the expression system, and introduce ``powi()`` as
+  an alternative exponentiation function for natural exponents
+  (`#98 <https://github.com/bluescarni/heyoka/pull/98>`__).
 - Implement propagation over a time grid
   (`#95 <https://github.com/bluescarni/heyoka/pull/95>`__).
 - Implement support for dense output
@@ -16,6 +23,13 @@ New
   integrator classes
   (`#91 <https://github.com/bluescarni/heyoka/pull/91>`__).
 
+Fix
+~~~
+
+- Avoid division by zero in certain corner cases
+  when using ``pow()`` with small natural exponents
+  (`#98 <https://github.com/bluescarni/heyoka/pull/98>`__).
+
 0.3.0 (2021-02-11)
 ------------------
 

include/heyoka/math.hpp

@@ -20,6 +20,7 @@
 #include <heyoka/math/erf.hpp>
 #include <heyoka/math/exp.hpp>
 #include <heyoka/math/log.hpp>
+#include <heyoka/math/neg.hpp>
 #include <heyoka/math/pow.hpp>
 #include <heyoka/math/sigmoid.hpp>
 #include <heyoka/math/sin.hpp>

include/heyoka/math/neg.hpp

@@ -0,0 +1,68 @@
+// Copyright 2020, 2021 Francesco Biscani ([email protected]), Dario Izzo ([email protected])
+//
+// This file is part of the heyoka library.
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef HEYOKA_MATH_NEG_HPP
+#define HEYOKA_MATH_NEG_HPP
+
+#include <cstdint>
+#include <ostream>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include <heyoka/config.hpp>
+#include <heyoka/detail/fwd_decl.hpp>
+#include <heyoka/detail/llvm_fwd.hpp>
+#include <heyoka/detail/visibility.hpp>
+#include <heyoka/func.hpp>
+
+namespace heyoka
+{
+
+namespace detail
+{
+
+class HEYOKA_DLL_PUBLIC neg_impl : public func_base
+{
+public:
+    neg_impl();
+    explicit neg_impl(expression);
+
+    void to_stream(std::ostream &) const;
+
+    llvm::Value *codegen_dbl(llvm_state &, const std::vector<llvm::Value *> &) const;
+    llvm::Value *codegen_ldbl(llvm_state &, const std::vector<llvm::Value *> &) const;
+#if defined(HEYOKA_HAVE_REAL128)
+    llvm::Value *codegen_f128(llvm_state &, const std::vector<llvm::Value *> &) const;
+#endif
+
+    llvm::Value *taylor_diff_dbl(llvm_state &, const std::vector<std::uint32_t> &, const std::vector<llvm::Value *> &,
+                                 llvm::Value *, llvm::Value *, std::uint32_t, std::uint32_t, std::uint32_t,
+                                 std::uint32_t) const;
+    llvm::Value *taylor_diff_ldbl(llvm_state &, const std::vector<std::uint32_t> &, const std::vector<llvm::Value *> &,
+                                  llvm::Value *, llvm::Value *, std::uint32_t, std::uint32_t, std::uint32_t,
+                                  std::uint32_t) const;
+#if defined(HEYOKA_HAVE_REAL128)
+    llvm::Value *taylor_diff_f128(llvm_state &, const std::vector<std::uint32_t> &, const std::vector<llvm::Value *> &,
+                                  llvm::Value *, llvm::Value *, std::uint32_t, std::uint32_t, std::uint32_t,
+                                  std::uint32_t) const;
+#endif
+    llvm::Function *taylor_c_diff_func_dbl(llvm_state &, std::uint32_t, std::uint32_t) const;
+    llvm::Function *taylor_c_diff_func_ldbl(llvm_state &, std::uint32_t, std::uint32_t) const;
+#if defined(HEYOKA_HAVE_REAL128)
+    llvm::Function *taylor_c_diff_func_f128(llvm_state &, std::uint32_t, std::uint32_t) const;
+#endif
+};
+
+} // namespace detail
+
+HEYOKA_DLL_PUBLIC expression neg(expression);
+
+} // namespace heyoka
+
+#endif

src/expression.cpp

@@ -37,6 +37,7 @@
 #include <heyoka/expression.hpp>
 #include <heyoka/func.hpp>
 #include <heyoka/llvm_state.hpp>
+#include <heyoka/math/neg.hpp>
 #include <heyoka/math/square.hpp>
 #include <heyoka/number.hpp>
 #include <heyoka/param.hpp>
@@ -200,7 +201,11 @@ expression operator+(expression e)
 
 expression operator-(expression e)
 {
-    return expression{number{-1.}} * std::move(e);
+    if (auto num_ptr = std::get_if<number>(&e.value())) {
+        return expression{-std::move(*num_ptr)};
+    } else {
+        return neg(std::move(e));
+    }
 }
 
 expression operator+(expression e1, expression e2)