http://pc.freeshell.org/ 2009-11-21T12:50:24+00:00 http://pc.freeshell.org/ http://pc.freeshell.org/lib/images/favicon.ico text/html 2007-07-09T15:23:49+00:00 http://pc.freeshell.org/comp/bash?rev=1183994629 Conditional operators operator produces true if... no. of operands -n operand has non zero length 1 -z operand has zero length 1 -d there exists a directory whose name is operand 1 -f there exists a file whose name is operand 1 -eq the operands are integers and they are equal 2 -neq the opposite of -eq 2 = the operands are equal (as strings) 2 != opposite of = 2 -lt operand1 is strictly less than operand2 (both operands sho… text/html 2008-04-25T15:57:09+00:00 http://pc.freeshell.org/comp/fortran?rev=1209139029 * Using C/C++ and fortran together * IBM fortran manual * Mistakes in Fortran 90 Programs That Might Surprise You * Avoiding the Unnecessary Recompilation of Fortran 90 Modules Fortran compilers There are several free fortran compilers available now. GCC has a sufficiently good compiler called gfortran. Another free compiler is g95 which is the work of Andy Vaught. If you are using Linux then the ifort compiler from Intel is also free for non-commercial use, and probably the best choi… text/html 2006-12-18T10:17:30+00:00 http://pc.freeshell.org/comp/ibook?rev=1166437050 Hardware information (use lshw) to get much better information) Installation I deleted OSX and did a Linux only installation. Why waste the meagre 30G space when I wont need OSX. Follow the instructions in the Gentoo handbook. I did a stage 2 installation and downloaded the latest Linux kernel 2.6.16 and compiled it myself. Sleep works finally !!! text/html 2007-01-28T20:49:14+00:00 http://pc.freeshell.org/comp/latex?rev=1170017354 Boxed equation Define a new command as follows: Here is an example of its use: If you dont want to box the equation number, use \boxed{…} text/html 2008-11-20T11:38:55+00:00 http://pc.freeshell.org/comp/macbook?rev=1227181135 After three years with ibook G4 it was time to get a new laptop. And I decided to stick with Apple. This time I am going to give Mac a try instead of installing Linux. Leopard comes with a huge collection of tools pre-installed. Xcode 3.0 has almost everything that a developer needs: gcc, openmpi, svn, perl, python, ruby, lapack, blas, etc. I only had to install a fortran compiler and recompile openmpi to get fortran support. The default openmpi in Leopard does not have fortran support. I insta… text/html 2007-07-20T11:54:53+00:00 http://pc.freeshell.org/comp/misc?rev=1184932493 Indent a C/C++ code Indent is a wonderful program to format a c/c++ code in order to improve its readability. It has a lot of options to control formatting of different elements. I use the following options: Convert a bunch of files Use the mogrify command to convert a bunch of files from one format to another. Example: To convert all ps and eps files in some directory to pdf format, use text/html 2007-01-19T14:08:08+00:00 http://pc.freeshell.org/comp/precision?rev=1169215688 Machine precision is the smallest number eps such that the difference between 1 and 1 + eps is nonzero, ie., it is the smallest difference between two numbers that the computer recognizes. On a 32 bit computer, single precision is 2-23 (approximately 10-7) while double precision is 2-52 (approximately10-16) . The following fortran program finds the machine precision (This is based on a usenet posting by Guido Pagnacco). text/html 2006-11-16T08:53:07+00:00 http://pc.freeshell.org/comp/scilab?rev=1163667187 Beware of un-declared variables Scilab has a unique feature which is potentially dangerous and can make debugging very difficult. This has to do with un-initialized variables. Let me give an example. In the code below, func1 calls func2 and func2 is supposed to return the average value of its input vector x. text/html 2007-01-09T14:27:47+00:00 http://pc.freeshell.org/comp/svn?rev=1168352867 Subversion is a revision control system which is very useful for managing large software projects involving multiple authors. I wrote a ruby script for managing the commits to an svn repository. It is my first ruby program, so there is lot of scope for improvement. text/html 2009-07-02T09:22:19+00:00 http://pc.freeshell.org/comp/tifr-cluster?rev=1246526539 Hardware and software Feature Available Number of nodes 16 Number of cores 104 RAM 1 GB/core, total 104 GB Interconnect Gigabit ethernet Operating system CentOS 5, Rocks 5 Compilers gcc 4.1.2, gfortran 4.1.2, pgi 7.2-2 MPI MPICH2, OpenMPI Torque/PBS The nodes are put into two groups, see the file /opt/torque/server_priv/nodes text/html 2008-06-28T12:00:45+00:00 http://pc.freeshell.org/comp/vim?rev=1214654445 vimrc Below I have listed some settings in vim which make your editing life easier. * Disabling file backups: Vim makes backups of files which are edited. Disable this with * Disable displaying line numbers with * If you enable the showmatch option, then whenever you start and close a bracket, then it automatically shows the matching brackets. This is useful for some programming languages like C.