<html><head><meta http-equiv="content-type" content="text/html; charset=us-ascii"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><font size="4" face="Arial">Dear <span style="orphans: 2; text-wrap-mode: wrap; widows: 2;">PETSc developers,</span></font><div><span style="orphans: 2; text-wrap-mode: wrap; widows: 2;"><font size="4" face="Arial"><br></font></span></div><div><span style="orphans: 2; widows: 2;"><font size="4" face="Arial">I use PETSc and SLEPC to solve generalized eigen problems. When solving an interval eigen problem with matrix size about 5 million, i got the error message: "product of two integer xx xx overflow, you must ./configure PETSc with --with-64-bit-indices for the case you are running".</font></span></div><div><span style="orphans: 2; widows: 2;"><font size="4" face="Arial"><br></font></span></div><div style="orphans: 2; widows: 2;"><font face="Arial" size="4">I use some prebuilt third-party packages when building PETSc, namely OpenBLAS, METIS, ParMETIS and SCALAPACK. I wonder should i also use 64-bit prebuilt packages when configure PETSc with the </font><span style="font-family: Arial; font-size: large;">--with-64-bit-indices flag? How about the MUMPS and MPI? Do i have to also use the b4-bit version?</span></div><div style="orphans: 2; widows: 2;"><span style="font-family: Arial; font-size: large;"><br></span></div><div style="orphans: 2; widows: 2;"><span style="font-family: Arial; font-size: large;">Look forward for your reply, thanks.</span></div><div style="orphans: 2; widows: 2;"><span style="font-family: Arial; font-size: large;"><br></span></div><div style="orphans: 2; widows: 2;"><span style="font-family: Arial; font-size: large;">Xiaofeng</span></div></body></html>