From 65b2d85b8e62d3390d9bf1bb741f12e57d254ece Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bogumi=C5=82=20Kami=C5=84ski?= <bkamins@sgh.waw.pl>
Date: Fri, 3 Mar 2023 19:25:23 +0100
Subject: [PATCH] Add errata entry

---
 README.md | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

diff --git a/README.md b/README.md
index a8998a4..a9a2469 100644
--- a/README.md
+++ b/README.md
@@ -175,6 +175,55 @@ Kamiński, Bogumił. 2023. *Julia for Data Analysis*. Manning.
 
 ## Errata
 
+
+### Chapter 1, section 1.2.1, page 7
+
+I show the following example of code execution:
+
+```
+julia> function sum_n(n)
+           s = 0
+           for i in 1:n
+               s += i
+           end
+           return s
+       end
+sum_n (generic function with 1 method)
+
+julia> @time sum_n(1_000_000_000)
+  0.000001 seconds
+500000000500000000
+```
+
+This timining is very fast (and the reason is explained in the book).
+The issue is that this is the situation under Julia 1.7.
+
+Under Julia 1.8 and Julia 1.9 running the same code takes longer (tested under Julia 1.9-beta4):
+
+```
+julia> @time sum_n(1_000_000_000)
+  2.265569 seconds
+500000000500000000
+```
+
+The reason for this inconsistency is a bug in `@time` macro introduced in Julia 1.8 release.
+The `sum_n(1_000_000_000)` call (without `@time`) is executed fast.
+Here is a simplified benchmark (run under Julia 1.9-beta4):
+
+```
+julia> let
+           start = time_ns()
+           v = sum_n(1_000_000_000)
+           stop=time_ns()
+           v, Int(stop - start)
+       end
+(500000000500000000, 1000)
+```
+
+Unfortunately there is an issue with the `@time`
+macro used in global scope, that needs to be resolved in Base Julia.
+See [this issue](https://github.com/JuliaLang/julia/issues/47561).
+
 ### Chapter 2, section 2.3.1, page 30
 
 I compare the following expressions: