Hi everyone! I'm writing a FEM-program and at the moment I try to parallize the assembly of the stiffness-matrix. The idea would be if I for example use 4 threads I create 4 matrices and 4 rhs-vectors. Each thread fills its matrix and rhs-vector. At the end I add all matrices and vectors. But the Petsc-manual says that Petsc is not thread-safe. Is that the reason why it doesn't work? Usually I get those error-code (after assembling 4-100 elements - everytime different): I.) [0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation, probably memory access out of range or II.) *** glibc detected *** ../icona: corrupted double-linked list: 0x00000000166ff730 *** ======= Backtrace: ========= /lib64/libc.so.6[0x3a9fc72405] /lib64/libc.so.6(cfree+0x4b)[0x3a9fc7276b] ../icona[0x426cae] ../icona[0x42df99] ../icona[0x41b829] ../icona[0x416203] ../icona[0x417341] ../icona[0x408954] /lib64/libc.so.6(__libc_start_main+0xf4)[0x3a9fc1d994] ../icona(__gxx_personality_v0+0x3e9)[0x4078f9] ======= Memory map: ======== 00400000-00fe1000 r-xp 00000000 00:1b 143920732 /home/c7031006/icona2.zip_FILES/icona2/icona 011e1000-011e8000 rw-p 00be1000 00:1b 143920732 /home/c7031006/icona2.zip_FILES/icona2/icona 011e8000-0131b000 rw-p 011e8000 00:00 0 16397000-16724000 rw-p 16397000 00:00 0 [heap] If someone could explain - Thank you. Yours sincerely, Clemens Domanig