help-octave
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: inverse matrix


From: Mario Baussmann
Subject: Re: inverse matrix
Date: Mon, 17 Sep 2007 15:54:23 +0200
User-agent: Thunderbird 2.0.0.6 (Windows/20070728)

Hi,
on my computer (WindowsXP):

Processors Information
------------------------------------------------------------------------------------

Processor 1 (ID = 0)
Number of cores         1
Number of threads       2 (max 2)
Name                    Intel Pentium 4
Codename                Prescott
Specification           Intel(R) Pentium(R) 4 CPU 2.80GHz
Package                 Socket 478 mPGA (platform ID = 2h)
CPUID                   F.3.4
Extended CPUID          F.3
Core Stepping           D0
Technology              90 nm
Core Speed              2799.7 MHz (14.0 x 200.0 MHz)
Rated Bus speed         799.9 MHz
Stock frequency         2800 MHz
Instructions sets       MMX, SSE, SSE2, SSE3
L1 Data cache           16 KBytes, 8-way set associative, 64-byte line size
Trace cache             12 Kuops, 8-way set associative
L2 cache                1024 KBytes, 8-way set associative, 64-byte line size
FID/VID Control         no

this script:

a = [1.2500e+02, 1.4595e+01, 5.8551e-08, 4.9222e+02; 1.4595e+01, \
     1.0320e+01, -2.2343e-12, 1.7402e+02; 5.8551e-08, -2.2343e-12, \
     5.8688e+03, -1.5056e-11; 4.9222e+02, 1.7402e+02, -1.5056e-11, \
     8.8034e+03];
[x,rcond]=inverse(a)

produces with both versions 2.1.73 and 2.9.13 the same result for rcond:
6.5695...e-4.

regards
Mario

Ólafur Jens Sigurðsson schrieb:
Hi

I came across the following scenario:
For the following matrix

 1.0634e-02   -7.5196e-03   -1.0610e-13   -4.4593e-04
-7.5196e-03    1.5066e-01    7.5071e-14   -2.5578e-03
-1.0610e-13    7.5071e-14     1.7039e-04    4.4484e-15
-4.4593e-04   -2.5578e-03    4.4484e-15    1.8909e-04

the inverse in version 2.9.10 in debian produces rcond = 0 but in 2.1.73 it is rcond = 0.00065696

Does this happen in all machines or is this just me (a AMD Athlon 1344 MHz, cpu family 6, model 8 ... info taken from /proc/cpuinfo running debian unstable)?

If this is a general thing, is there a reason for why the 2.9.10 is worse in this then 2.1.73 (I would consider this to be worse, unless 2.1.73 is just doing wrong calculation).

Regards

Oli


reply via email to

[Prev in Thread] Current Thread [Next in Thread]