Remove psutil as a dependency

qiskit/providers/basicaer/qasm_simulator.py

@@ -31,11 +31,9 @@
 import logging
 import warnings
 
-from math import log2
 from collections import Counter
 import numpy as np
 
-from qiskit.utils.multiprocessing import local_hardware_info
 from qiskit.providers.models import QasmBackendConfiguration
 from qiskit.result import Result
 from qiskit.providers.backend import BackendV1
@@ -53,12 +51,10 @@
 class QasmSimulatorPy(BackendV1):
     """Python implementation of an OpenQASM 2 simulator."""
 
-    MAX_QUBITS_MEMORY = int(log2(local_hardware_info()["memory"] * (1024**3) / 16))
-
     DEFAULT_CONFIGURATION = {
         "backend_name": "qasm_simulator",
         "backend_version": "2.1.0",
-        "n_qubits": min(24, MAX_QUBITS_MEMORY),
+        "n_qubits": 24,
         "url": "https://github.com/Qiskit/qiskit-terra",
         "simulator": True,
         "local": True,

qiskit/providers/basicaer/statevector_simulator.py

@@ -24,8 +24,6 @@
 """
 
 import logging
-from math import log2
-from qiskit.utils.multiprocessing import local_hardware_info
 from qiskit.providers.basicaer.exceptions import BasicAerError
 from qiskit.providers.models import QasmBackendConfiguration
 from .qasm_simulator import QasmSimulatorPy
@@ -36,12 +34,10 @@
 class StatevectorSimulatorPy(QasmSimulatorPy):
     """Python statevector simulator."""
 
-    MAX_QUBITS_MEMORY = int(log2(local_hardware_info()["memory"] * (1024**3) / 16))
-
     DEFAULT_CONFIGURATION = {
         "backend_name": "statevector_simulator",
         "backend_version": "1.1.0",
-        "n_qubits": min(24, MAX_QUBITS_MEMORY),
+        "n_qubits": 24,
         "url": "https://github.com/Qiskit/qiskit-terra",
         "simulator": True,
         "local": True,

qiskit/providers/basicaer/unitary_simulator.py

@@ -27,13 +27,11 @@
 import logging
 import uuid
 import time
-from math import log2, sqrt
 import warnings
 
 import numpy as np
 
 from qiskit.circuit.quantumcircuit import QuantumCircuit
-from qiskit.utils.multiprocessing import local_hardware_info
 from qiskit.providers.models import QasmBackendConfiguration
 from qiskit.providers.backend import BackendV1
 from qiskit.providers.options import Options
@@ -55,12 +53,10 @@
 class UnitarySimulatorPy(BackendV1):
     """Python implementation of a unitary simulator."""
 
-    MAX_QUBITS_MEMORY = int(log2(sqrt(local_hardware_info()["memory"] * (1024**3) / 16)))
-
     DEFAULT_CONFIGURATION = {
         "backend_name": "unitary_simulator",
         "backend_version": "1.1.0",
-        "n_qubits": min(24, MAX_QUBITS_MEMORY),
+        "n_qubits": 24,
         "url": "https://github.com/Qiskit/qiskit-terra",
         "simulator": True,
         "local": True,

qiskit/utils/multiprocessing.py

@@ -14,8 +14,7 @@
 
 import multiprocessing as mp
 import platform
-
-import psutil
+import os
 
 
 def local_hardware_info():
@@ -27,13 +26,18 @@ def local_hardware_info():
     Returns:
         dict: The hardware information.
     """
+
+    if hasattr(os, "sched_getaffinity"):
+        num_cpus = int(len(os.sched_getaffinity(0)) / 2) or 1
+    else:
+        num_cpus = 1
+
     results = {
         "python_compiler": platform.python_compiler(),
         "python_build": ", ".join(platform.python_build()),
         "python_version": platform.python_version(),
         "os": platform.system(),
-        "memory": psutil.virtual_memory().total / (1024**3),
-        "cpus": psutil.cpu_count(logical=False) or 1,
+        "cpus": num_cpus,
     }
     return results
 

releasenotes/notes/psutil-dependancy-removed-bf5366f516d92378.yaml

@@ -0,0 +1,4 @@
+---
+upgrade:
+  - |
+    Removed psutil for detecting number of cpus and memory. the information provided does not add sufficient value to justify the additional dependencies and overhead.

requirements.txt

@@ -1,6 +1,5 @@
 rustworkx>=0.13.0
 numpy>=1.17,<2
-psutil>=5
 scipy>=1.5
 sympy>=1.3
 dill>=0.3

test/python/test_util.py

@@ -12,7 +12,8 @@
 
 """Tests for qiskit/utils"""
 
-from unittest import mock
+import os
+from unittest import mock, skipIf
 
 from qiskit.utils.multiprocessing import local_hardware_info
 from qiskit.test import QiskitTestCase
@@ -21,11 +22,11 @@
 class TestUtil(QiskitTestCase):
     """Tests for qiskit/_util.py"""
 
+    @skipIf(not hasattr(os, "sched_getaffinity"), "ched_getaffinity is only available on linux")
     @mock.patch("platform.system", return_value="Linux")
-    @mock.patch("psutil.virtual_memory")
-    @mock.patch("psutil.cpu_count", return_value=None)
-    def test_local_hardware_none_cpu_count(self, cpu_count_mock, vmem_mock, platform_mock):
+    @mock.patch("os.sched_getaffinity", return_value={})
+    def test_local_hardware_none_cpu_count(self, cpu_count_mock, platform_mock):
         """Test cpu count fallback to 1 when true value can't be determined"""
-        del cpu_count_mock, vmem_mock, platform_mock  # unused
+        del cpu_count_mock, platform_mock  # unused
         result = local_hardware_info()
         self.assertEqual(1, result["cpus"])

test/python/transpiler/test_mappers.py

@@ -294,7 +294,7 @@ class TestsSabreSwap(SwapperCommonTestCases, QiskitTestCase):
     """Test SwapperCommonTestCases using SabreSwap."""
 
     pass_class = SabreSwap
-    additional_args = {"seed": 1242}
+    additional_args = {"seed": 1242, "trials": 2}
 
 
 if __name__ == "__main__":