From: N. Brouard <brouard@ined.fr>
Date: Wed, 24 Apr 2024 20:53:06 +0000 (+0000)
Subject: Summary: First IMaCh version using praxis method and adapted C code from Gegenfürtner
X-Git-Tag: imach-099s7~30
X-Git-Url: https://henry.ined.fr/git/?a=commitdiff_plain;h=4a1123a87e9318ae45e00e60b8dcd1fe5942ef3f;p=.git

Summary: First IMaCh version using praxis method and adapted C code from Gegenfürtner
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diff --git a/src/ChangeLog b/src/ChangeLog
index 9831c4a..c0b0caa 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,60 @@
+2024-04-24  Nicolas Brouard   <brouard@ined.fr>
+
+	* (Module): This version comes late after having tested
+	successfully the praxis C version of Buckhardt.  But Buckardt's
+	version was difficult to read and Gegenfurtner's version had a few
+	typos which made its results less reliable than Buckhardt's
+	results.  The most important work consisted in retyping the Brent
+	original PRAXIS program written in Algol W (published with errors,
+	ommitting the transposition of matrix V before its QR reduction
+	from Golub. I used the recent "awe" compiler from Gkynn Webster.
+	The awe library had errors, for example in arc tangent function
+	which have been fixed.
+
+	The main objective was to get identical results with the three
+	versions: (1) Algol W, (2) Buckhardt'C version as well (3)
+	Gegenfürtner C versions on the various test functions published by
+	Brent in 1973 in Algol W.
+
+	Also, in order to compare them, the random function had to produce
+	the same sequence for the 3 softwares. The random function used in
+	imach corresponds to original Brent's random function written in
+	Algol W.  Other point, in Algol W, the arrays of dimension n are
+	'normal' mathematical arrays starting from 1 to n. But this is a
+	real issue in C where, by default, arrays are starting from 0 to
+	n-1. In Buckhardt, as well as in Gegenfürtner C code, it can be
+	seen that authors while trying to mimick original Brent Algol W
+	code are hesitating by changing either a loop originally from 1 to
+	n in a loop from 0 to n-1, or keeping Brent's loop from 1 to n and
+	shifting the index from original X(I) in Algol W to x[i-1] in C.
+	But as IMaCh is using, since the beginning, the Numerical Recipes
+	functions vector or matrix, I changed Geggenfürtner code to mimick
+	the original Algol W arrays. Thus the X(I) is translated in C as
+	x[i] which minimizes the errors. The Golub QR algorithm was
+	published in Algol with overflow errors which were reproduced in
+	Brent's Algol W code. Buckhardt code fixed these errors which are
+	much more problematic in C than in Algol W.  Thus Buckhardt code
+	seems very safe, but i haven't chosen it for IMaCh because the C
+	style is horrible and almost unreadable compared to Gegenfürtner
+	CO code which is very close to Brent's original. Also what makes
+	Buckhardt code more difficult to read is, instead of passing the
+	minimum of parameters in the functions calls, as it is in Algol
+	Brent's code or Gegenfürtner's code, the list of parameters is
+	high. For example, the flin function LONG REAL PROCEDURE FLIN
+	(LONG REAL VALUE L) has only one parameter in Algol W, the
+	Gegenfürtner flin function had two parameters: static double
+	flin(l, j) double l; { int i; double tflin[N];} but Buckhardt
+	function has 14 parameters which makes the code unreadable and
+	useless. Gegenfürtner used a lot of static variables or functions
+	which I tried to minimize. Also in Gegefürtner, array dimensions
+	were fixed to N. In my adaptation the flin is static double
+	flin(double l, int j) and the parameter used are global variables.
+
+2023-06-14  Nicolas Brouard   <brouard@ined.fr>
+
+	* imach.c (Module): Testing if conjugate gradient could be quicker
+	when lot of variables POWELLORIGINCONJUGATE
+
 2023-05-23  Nicolas Brouard   <brouard@ined.fr>
 
 	* imach.c (Module): Fixed PROB_r