#include "clapack.h" /* Subroutine */ int slabad_(real *small, real *large) { /* Builtin functions */ double r_lg10(real *), sqrt(doublereal); /* -- LAPACK auxiliary routine (version 3.1) -- */ /* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */ /* November 2006 */ /* .. Scalar Arguments .. */ /* .. */ /* Purpose */ /* ======= */ /* SLABAD 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 SLAMCH. This subroutine is needed because */ /* SLAMCH does not compensate for poor arithmetic in the upper half of */ /* the exponent range, as is found on a Cray. */ /* Arguments */ /* ========= */ /* SMALL (input/output) REAL */ /* On entry, the underflow threshold as computed by SLAMCH. */ /* On exit, if LOG10(LARGE) is sufficiently large, the square */ /* root of SMALL, otherwise unchanged. */ /* LARGE (input/output) REAL */ /* On entry, the overflow threshold as computed by SLAMCH. */ /* On exit, if LOG10(LARGE) is sufficiently large, the square */ /* root of LARGE, otherwise unchanged. */ /* ===================================================================== */ /* .. Intrinsic Functions .. */ /* .. */ /* .. Executable Statements .. */ /* If it looks like we're on a Cray, take the square root of */ /* SMALL and LARGE to avoid overflow and underflow problems. */ if (r_lg10(large) > 2e3f) { *small = sqrt(*small); *large = sqrt(*large); } return 0; /* End of SLABAD */ } /* slabad_ */