LAPACKE_dgeqrf hangs with omp dynamic enabled

JohhnyEnglish — Sat, 01 Aug 2026 19:26:45 GMT

I've been having an issue where scipy's svd hangs in mkl. My investigation seems to suggest its an issue where mkl is assuming it has 4 workers and is stuck waiting for them when it only has 1, due to me setting OMP_DYNAMIC=TRUE and omp reducing the number of workers when the machine is busy.

Repro which was using the python `mkl-devel==2026.1.0` package:

#define _GNU_SOURCE #include <mkl.h> #include <omp.h> #include <sched.h> #include <stdio.h> static double a[3000 * 128]; static double tau[128] int main(void) { cpu_set_t cpus; /* We pin to one CPU to simulate OMP's behaviour when the load average on the machine is high. In dynamic mode this causes it to lower the maximum threading. */ CPU_ZERO(&cpus); CPU_SET(sched_getcpu(), &cpus); if (sched_setaffinity(0, sizeof(cpus), &cpus) != 0) { perror("sched_setaffinity"); return 1; } omp_set_dynamic(1); mkl_set_dynamic(0); mkl_set_num_threads_local(4); puts("starting DGEQRF"); fflush(stdout); return LAPACKE_dgeqrf(LAPACK_COL_MAJOR, 3000, 128, a, 3000, tau) }

Let me know if any more information would be useful

topic LAPACKE_dgeqrf hangs with omp dynamic enabled in Intel® oneAPI Math Kernel Library

LAPACKE_dgeqrf hangs with omp dynamic enabled