From f8722d817b1b8d1f7e138105f982a8a2f8c960bb Mon Sep 17 00:00:00 2001
From: Orestis <orestis.malaspinas@pm.me>
Date: Wed, 27 Oct 2021 11:01:12 +0200
Subject: [PATCH] updated path for complexity slides
---
slides/complexite.md | 29 +++++++++++++++++++++++------
1 file changed, 23 insertions(+), 6 deletions(-)
diff --git a/slides/complexite.md b/slides/complexite.md
index 4c49e66..81cbb89 100644
--- a/slides/complexite.md
+++ b/slides/complexite.md
@@ -13,19 +13,36 @@ Comment mesurer l'efficacité d'un algorithme?
Dépendant du **matériel**, du **compilateur**, des **options de compilation**,
etc!
-## Exemple: somme d'entiers
+## Mesure du temps CPU
```C
#include <time.h>
-
struct timespec tstart={0,0}, tend={0,0};
clock_gettime(CLOCK_MONOTONIC, &tstart);
// some computation
clock_gettime(CLOCK_MONOTONIC, &tend);
+printf("computation about %.5f seconds\n",
+ ((double)tend.tv_sec + 1e-9*tend.tv_nsec) -
+ ((double)tstart.tv_sec + 1e-9*tstart.tv_nsec));
+```
+
+# Programme simple: mesure du temps CPU
-printf("some_long_computation took about %.5f seconds\n",
- ((double)tend.tv_sec + 1.0e-9*tend.tv_nsec) -
- ((double)tstart.tv_sec + 1.0e-9*tstart.tv_nsec));
+## Preuve sur un [petit exemple](../source_codes/complexity/sum.c)
+
+```bash
+source_codes/complexity$ make bench
+RUN ONCE O0
+the computation of 199972.740622 took about 0.00836 seconds
+RUN ONCE O3
+the computation of 199972.740622 took about 0.00203 seconds
+RUN THOUSAND TIMES O0
+the computation of 199972740.621922 took about 0.00363 seconds
+RUN THOUSAND TIMES O3
+the computation of 199972740.621922 took about 0.00046 seconds
```
-* Il est nécessaire d'avoir une mesure indépendante du matériel.
+. . .
+
+* Il est nécessaire d'avoir une mesure indépendante du
+ matériel/compilateur/façon de mesurer.
--
GitLab