KNOWN PROBLEMS WITH INSTALLING XIDL AND/OR FIREHOSE

We are aware that some users have encountered difficulties installing xidl, but we have not been able to verify this on every possible platform.  If you have encountered a problem or found a solution for a particular configuration, please add a comment to this wiki so that we can pass along your information to future users.

• Problem: On some architectures IDL reports problems loading shared execuable libraries using call_external, possibly from 32 versus 64 bit conflicts.
  • Solution: The SDSS idlutils package only runs in 32 bit mode, so you need to start idl using the "idl -32" command.  Also, xidl will compile by default into 64 bit mode unless you tell it otherwise.  To force xidl to compile in 32 bit mode, go into $XIDL_DIR/src/Makefile.  Add option "-m32" to both the CFLAGS line and also right after the $(X_LD_FLAGS) field in the line starting with $(LD).

KNOWN BUGS OR DEFICIENCIES IN THE FIREHOSE SUITE

1. The wavelength calibration and sky subtraction are not yet perfected, resulting in some residuals in sky subtracted images and mismatch of sky lines in wavelength space for adjacent orders.  It is *pretty* good, but we'd like residuals at the 0.1 pixel level and are continuing to work on this problem.  Current RMS in the wavelength fit is ~0.3-0.5 pixels.

2. The code currently crashes when attempting to combine the reddest order into the final 1d spectrum.  For this reason we have restricted the combine operation to one order below this.  It appears to be a bookkeeping error and will be fixed (we hope) in the next release.