Specify the --cpu 4 but only 1 cpu was utilized

[zuopengl]

Dears,

Describe the bug
I specified the option --cpu with 4, but finally only 1 was used and low memory was utilized. It makes the step of Overlapping-graph building very slow.

Expected behavior
I wish it can process Overlapping-graph building parallelly to shorten the time.

Screenshots

You can see the following screenshots about runtime. The process only completed 1.2% with 1 cpu after running 2 days. Though the command line pointed 4 cpus but only used 1

Desktop (please complete the following information):
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"

the following is conda list of conda environment

the conda version is conda 23.1.0

Look forward to hearing from you!

Best regards!
Zuopeng