From e2dcd95407d5202019cecd2bb2827ee6a4a8f9f3 Mon Sep 17 00:00:00 2001
From: Aaron Gokaslan <skylion.aaron@gmail.com>
Date: Mon, 6 Jun 2022 22:33:28 -0400
Subject: [PATCH] chore: optimize dictionary access in strip_padding numpy
 (#3994)

* emplace field descriptors

* reserve sufficient capacity

* remove std::move

* properly iterate through dict

* make handle casting more explicit

* Revert to old dict api
---
 include/pybind11/numpy.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 0c77a98dd..43784f8e9 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -641,10 +641,14 @@ private:
             pybind11::str name;
             object format;
             pybind11::int_ offset;
+            field_descr(pybind11::str &&name, object &&format, pybind11::int_ &&offset)
+                : name{std::move(name)}, format{std::move(format)}, offset{std::move(offset)} {};
         };
+        auto field_dict = attr("fields").cast<dict>();
         std::vector<field_descr> field_descriptors;
+        field_descriptors.reserve(field_dict.size());
 
-        for (auto field : attr("fields").attr("items")()) {
+        for (auto field : field_dict.attr("items")()) {
             auto spec = field.cast<tuple>();
             auto name = spec[0].cast<pybind11::str>();
             auto spec_fo = spec[1].cast<tuple>();
@@ -653,8 +657,8 @@ private:
             if ((len(name) == 0u) && format.kind() == 'V') {
                 continue;
             }
-            field_descriptors.push_back(
-                {(pybind11::str) name, format.strip_padding(format.itemsize()), offset});
+            field_descriptors.emplace_back(
+                std::move(name), format.strip_padding(format.itemsize()), std::move(offset));
         }
 
         std::sort(field_descriptors.begin(),