Revert SQRT2 definition to v0.31.0 (#479)

* Do not import numbers header in main code.

* Auto update version

* Update changelog.

* Fix INVSQRT2

* Cannot use sqrt on Windows/Mac.

* Build doc with PL@master.

* Revert SQTR2 to old def.

* Update requirements.txt

---------

Co-authored-by: Dev version update bot <github-actions[bot]@users.noreply.github.com>

Author: vincentmr

.github/CHANGELOG.md

@@ -21,6 +21,9 @@
 
 ### Bug fixes
 
+* Do no import `sqrt2_v` from `<numbers>` in `Util.hpp` to resolve issue with Lightning-GPU builds.
+  [(#479)](https://github.com/PennyLaneAI/pennylane-lightning/pull/479)
+
 * Update the CMake internal references to enable sub-project compilation with affecting the parent package.
   [(#478)](https://github.com/PennyLaneAI/pennylane-lightning/pull/478)
 

pennylane_lightning/core/_version.py

@@ -16,4 +16,4 @@
    Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.32.0-dev9"
+__version__ = "0.32.0-dev10"

pennylane_lightning/core/src/simulators/lightning_qubit/algorithms/tests/Test_VectorJacobianProduct.cpp

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 #include <algorithm>
+#include <numbers>
 #include <random>
 #include <span>
 #include <vector>

pennylane_lightning/core/src/utils/Util.hpp

@@ -20,7 +20,7 @@
 
 #include <cmath>
 #include <complex>
-#include <numbers> // sqrt2_v
+#include <numbers>
 #include <numeric> // transform_reduce
 #include <set>
 #include <type_traits> // is_same_v
@@ -175,7 +175,15 @@ inline static constexpr auto IMAG() -> ComplexT<T> {
  * @return constexpr T sqrt(2)
  */
 template <class T> inline static constexpr auto SQRT2() -> T {
+#if __cpp_lib_math_constants >= 201907L
     return std::numbers::sqrt2_v<T>;
+#else
+    if constexpr (std::is_same_v<T, float>) {
+        return 0x1.6a09e6p+0F; // NOLINT: To be replaced in C++20
+    } else {
+        return 0x1.6a09e667f3bcdp+0; // NOLINT: To be replaced in C++20
+    }
+#endif
 }
 
 /**
@@ -187,7 +195,15 @@ template <class T> inline static constexpr auto SQRT2() -> T {
  */
 template <template <class> class ComplexT, class T>
 inline static constexpr auto SQRT2() -> ComplexT<T> {
+#if __cpp_lib_math_constants >= 201907L
     return std::numbers::sqrt2_v<T>;
+#else
+    if constexpr (std::is_same_v<T, float>) {
+        return 0x1.6a09e6p+0F; // NOLINT: To be replaced in C++20
+    } else {
+        return 0x1.6a09e667f3bcdp+0; // NOLINT: To be replaced in C++20
+    }
+#endif
 }
 
 /**
@@ -209,7 +225,7 @@ template <class T> inline static constexpr auto INVSQRT2() -> T {
  */
 template <template <class> class ComplexT, class T>
 inline static constexpr auto INVSQRT2() -> ComplexT<T> {
-    return {1 / SQRT2<T>()};
+    return static_cast<ComplexT<T>>(INVSQRT2<T>());
 }
 
 /**