On Wed, 25 Nov 2009, Lisandro Dalcin wrote:

I said this before, but let's go one more time: I find --prefix installs of PETSc a bit useless for general-purpose installations. Supose as sysadmin "make install" PETSc in a cluster. She likely built using a C as language, double precision real scalars, 32bit integers, (dbg/opt?). Such configuration does not fit all applications. Some users may require C++, other may want complex, others may want to run her own codes with a debug version. Then I see VERY little point on --prefix builds of PETSc. Moreover, in our machines at CIMEC I maintain central installations of PETSc at /usr/local/petsc/3.0.0. This is not done at all with --prefix and "make install", instead, "/usr/local/petsc/3.0.0" is a HG clone of release-3.0.0.

The idea with prefix & PETSc is - one does not use the same prefix for all installs. Here PETSC_DIR+PETSC_ARCH is the unique key from the usage side. no prefix mode: [only PETSC_ARCH changes] PETSC_ARCH=build1 PETSC_ARCH=build2 prefix mode: [only PETSC_DIR - which is the prefix value, is changed] prefix=/path1 prefix=/path2 Note: [using a different prefix path for different installs] is a common thing to do with autoconf packages as well. The difference with PETSc is - for the rest of the world [of packages] - a single install usually suffices. But for PETSc - we need multiple installs. I still stick with the default model when installing petsc on clusters. as switching 'only PETSC_ARCH' is more userfriendly. [and its easier for me to install in this mode] Satish