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Ticket Resolution Summary Owner Reporter
#66 fixed Lapack hangs in dlamc1 if in optimized build andreasw stefan


in some cases, CBC (2.1 stable) and SCIP (1.0; using Clp as LP solver) hang in the Lapack routine dlamc1 if I have compiled in optimized mode (i.e., default).

The compiler is a GCC 4.2.1, the machine a Intel Core2 Duo.

John pointed me to this ticket in the Octave mailing list. I followed the suggestions there and the problem went away when I added -ffloat-store to the FFLAGS.

Should this flag be added per default (when gcc is used), at least for dlamch.f ?

Best, Stefan

PS: This is from the gcc manual on what -ffloat-store is doing:

Do not store floating point variables in registers, and inhibit other options that might change whether a floating point value is taken from a register or memory.

This option prevents undesirable excess precision on machines such as the 68000 where the floating registers (of the 68881) keep more precision than a "double" is supposed to have. Similarly for the x86 architecture. For most programs, the excess precision does only good, but a few programs rely on the precise definition of IEEE floating point. Use -ffloat-store for such programs, after modifying them to store all pertinent intermediate computations into variables.

#67 fixed Running configure without g++ => cryptic error andreasw plb

While setting up bcp (with CoinUtils?? 2.2.5), I ran into the following problem :

configure: error: Cannot find integer type with 64 bits configure: error: /bin/bash '../../CoinUtils?/configure' failed for CoinUtils?

I'm enclosing config.log.

I tried several times. I had gcc installed, but not g++. I set up g++ and ran configure, and it went just fine. I'm enclosing the config.log of the successful run. If the failure was indeed caused by the absence of g++, it might be useful to make the error message more specific.

#68 fixed User-given FFLAGS ignored for dlamch compilation andreasw andreasw

Hi Stefan :-)

The compilation of dlamch still has some problems. For example, if someone sets FFLAGS, this is completely ignored when compiling it. (In an IBM context, someone had -fPIC included in FFLAGS and uses --disable-shared, so this doesn't work when you later try to make a shared library)

Instead of setting it to the coin_warn_flags etc, would it make more sense to scan the content of FFLAGS and remove anything of the form '-O*' and replace it by '-O0'? Not sure if that works for all compilers though (Windoofs?). At the very least, we should make DLAMCH_FFLAGS an argument that one can set.

What do you think?


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