#include "f2c.h" /* Subroutine */ int dlabad_(doublereal *small, doublereal *large) { /* -- LAPACK auxiliary routine (version 2.0) -- Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., Courant Institute, Argonne National Lab, and Rice University October 31, 1992 Purpose ======= DLABAD takes as input the values computed by SLAMCH for underflow and overflow, and returns the square root of each of these values if the log of LARGE is sufficiently large. This subroutine is intended to identify machines with a large exponent range, such as the Crays, and redefine the underflow and overflow limits to be the square roots of the values computed by DLAMCH. This subroutine is needed because DLAMCH does not compensate for poor arithmetic in the upper half of the exponent range, as is found on a Cray. Arguments ========= SMALL (input/output) DOUBLE PRECISION On entry, the underflow threshold as computed by DLAMCH. On exit, if LOG10(LARGE) is sufficiently large, the square root of SMALL, otherwise unchanged. LARGE (input/output) DOUBLE PRECISION On entry, the overflow threshold as computed by DLAMCH. On exit, if LOG10(LARGE) is sufficiently large, the square root of LARGE, otherwise unchanged. ===================================================================== If it looks like we're on a Cray, take the square root of SMALL and LARGE to avoid overflow and underflow problems. */ /* Builtin functions */ double d_lg10(doublereal *), sqrt(doublereal); if (d_lg10(large) > 2e3) { *small = sqrt(*small); *large = sqrt(*large); } return 0; /* End of DLABAD */ } /* dlabad_ */