[Question] SIGILL on non-AVX2 CPU when running ./apps/build_memory_index

[xwt1]

Hello!
My CPU architecture and supported instruction sets are shown at the bottom. As you can see, the CPU does not support AVX2. After compiling and running the example in
, running ./apps/build_memory_index crashes. I checked the core dump (see below), and it looks like an instruction corresponding to the AVX2 ISA is not available on this machine.

Therefore, if I can only run DiskANN on this machine, how should I set the build options? Do you have any recommended settings for a CPU that supports AVX but not AVX2?

Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
--Type <RET> for more, q to quit, c to continue without paging--
Core was generated by `./apps/build_memory_index --data_type float --dist_fn l2 --data_path data/sift/'.
Program terminated with signal SIGILL, Illegal instruction.
#0  0x000056308cc03ac8 in diskann::DistanceL2Float::compare(float const*, float const*, unsigned int) const ()
[Current thread is 1 (Thread 0x7f28eb7a9ac0 (LWP 62787))]
(gdb) bt
#0  0x000056308cc03ac8 in diskann::DistanceL2Float::compare(float const*, float const*, unsigned int) const ()
#1  0x000056308cf9fa0f in diskann::InMemDataStore<float>::get_distance(float const*, unsigned int const*, unsigned int, float*, diskann::AbstractScratch<float>*) const ()
#2  0x000056308cc63e15 in diskann::Index<float, unsigned int, unsigned int>::iterate_to_fixed_point(diskann::InMemQueryScratch<float>*, unsigned int, std::vector<unsigned int, std::allocator<unsigned int> > const&, bool, std::vector<unsigned int, std::allocator<unsigned int> > const&, bool) ()
#3  0x000056308cc64842 in diskann::Index<float, unsigned int, unsigned int>::search_for_point_and_prune(int, unsigned int, std::vector<unsigned int, std::allocator<unsigned int> >&, diskann::InMemQueryScratch<float>*, bool, unsigned int) ()
#4  0x000056308cf82673 in diskann::Index<float, unsigned int, unsigned int>::link() [clone ._omp_fn.0] ()
#5  0x00007f28f4e5a727 in ?? () from /lib/x86_64-linux-gnu/libomp.so.5
--Type <RET> for more, q to quit, c to continue without paging--
#6  0x00007f28f4e78623 in __kmp_invoke_microtask () from /lib/x86_64-linux-gnu/libomp.so.5
#7  0x00007f28f4dec3a9 in ?? () from /lib/x86_64-linux-gnu/libomp.so.5
#8  0x00007f28f4deac42 in ?? () from /lib/x86_64-linux-gnu/libomp.so.5
#9  0x00007f28f4e5284b in ?? () from /lib/x86_64-linux-gnu/libomp.so.5
#10 0x00007f28eb83fac3 in start_thread (arg=<optimized out>) at ./nptl/pthread_create.c:442
#11 0x00007f28eb8d1850 in clone3 () at ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
(gdb) 
(gdb) q

My build method follows microsoft/DiskANN#500
:

cmake -S . -B build -DPORTABLE=True
cmake --build build -- -j #like 99% sure this is right, I've been off for two weeks and don't remember how anything works anymore

My machine configuration:

Architecture:                x86_64
  CPU op-mode(s):            32-bit, 64-bit
  Address sizes:             46 bits physical, 48 bits virtual
  Byte Order:                Little Endian
CPU(s):                      16
  On-line CPU(s) list:       0-15
Vendor ID:                   GenuineIntel
  Model name:                Intel(R) Xeon(R) CPU E5-2450 0 @ 2.10GHz
    CPU family:              6
    Model:                   45
    Thread(s) per core:      2
    Core(s) per socket:      8
    Socket(s):               1
    Stepping:                7
    CPU max MHz:             2900.0000
    CPU min MHz:             1200.0000
    BogoMIPS:                4200.00
    Flags:                   fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmo
                             v pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe 
                             syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs 
                             bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni
                              pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 
                             xtpr pdcm pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_
                             timer aes xsave avx lahf_lm pti ssbd ibrs ibpb stibp tpr_sha
                             dow vnmi flexpriority ept vpid xsaveopt dtherm ida arat pln 
                             pts md_clear flush_l1d
Virtualization features:     
  Virtualization:            VT-x
Caches (sum of all):         
  L1d:                       256 KiB (8 instances)
  L1i:                       256 KiB (8 instances)
  L2:                        2 MiB (8 instances)
  L3:                        20 MiB (1 instance)
NUMA:                        
  NUMA node(s):              1
  NUMA node0 CPU(s):         0-15
Vulnerabilities:             
  Gather data sampling:      Not affected
  Indirect target selection: Not affected
  Itlb multihit:             KVM: Mitigation: VMX disabled
  L1tf:                      Mitigation; PTE Inversion; VMX conditional cache flushes, SM
                             T vulnerable
  Mds:                       Mitigation; Clear CPU buffers; SMT vulnerable
  Meltdown:                  Mitigation; PTI
  Mmio stale data:           Unknown: No mitigations
  Reg file data sampling:    Not affected
  Retbleed:                  Not affected
  Spec rstack overflow:      Not affected
  Spec store bypass:         Mitigation; Speculative Store Bypass disabled via prctl and 
                             seccomp
  Spectre v1:                Mitigation; usercopy/swapgs barriers and __user pointer sani
                             tization
  Spectre v2:                Mitigation; Retpolines; IBPB conditional; IBRS_FW; STIBP con
                             ditional; RSB filling; PBRSB-eIBRS Not affected; BHI Not aff
                             ected
  Srbds:                     Not affected
  Tsx async abort:           Not affected

I appreciate any suggestion!