Errors in vector processing and the library libavi.a

In this paper, we describe the r~ults of several tests that check the accuracy of numerical computation on the Cray sttpercomputer in vector and scalar mod~s. The known tests were mtwlified to identify the critical ~}int where rtmndings start causing problems. After describing the tests, we present ;in interval library called libavi.a. It was developed in Fortran 90 on the Cray Y-MP2E supercomputer of UFRGS-Brazil. This library makes interval mathematics accessible to the Cray supercomputers usens. It works with real and complex intervals and intervals matrice¢ and vectors. The library allows overloading of operators and fimctions. It is organized in timr modules: real intervals, interval vectors and matrices, complex intervals, and linear algebra applic, atitms.