Remove psutil as a dependency (Qiskit#11336)

* initial commit

* fixed missing import

* set sabreswap test trials to 2

* added check to determin number of cpus

* formatting error

* unittest excetion for hardware detection

* formatting error

* Fix handling of non-linux default CPU usage

* Update release note

* Expand testing

* Remove unused import

* Update mock to work on non-linux platforms

* Fix lint

---------

Co-authored-by: Matthew Treinish <[email protected]>

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

@@ -19,20 +19,18 @@
 
     UnitarySimulator().run(run_input)
 
-Where the input is a either Qobj object (deprecated) or QuantumCircuit or a list of circuits and 
-the output is a BasicAerJob object, which can later be queried for the Result object. The result 
+Where the input is a either Qobj object (deprecated) or QuantumCircuit or a list of circuits and
+the output is a BasicAerJob object, which can later be queried for the Result object. The result
 will contain a 'unitary' data field, which is a 2**n x 2**n complex numpy array representing the
 circuit's unitary matrix.
 """
 import logging
 import uuid
 import time
-from math import log2, sqrt
 import warnings
 
 import numpy as np
 
-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
@@ -54,12 +52,10 @@
 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 +26,22 @@ def local_hardware_info():
     Returns:
         dict: The hardware information.
     """
+
+    if hasattr(os, "sched_getaffinity"):
+        num_cpus = len(os.sched_getaffinity(0))
+    else:
+        num_cpus = os.cpu_count()
+    if num_cpus is None:
+        num_cpus = 1
+    else:
+        num_cpus = int(num_cpus / 2) or 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 +1,14 @@
+---
+upgrade:
+  - |
+    The dependency on `psutil <https://pypi.org/project/psutil/>`__ has been removed. The
+    psutil library was previously only used for detecting the number of physical CPUs and
+    total system memory, however this information provided does not add sufficient value
+    to justify the additional dependencies and overhead so it has been removed. This does
+    mean that the default number of processes used by :func:`.parallel_map` and functions that
+    internally can use :func:`.parallel_map` such as :func:`.transpile` and :meth:`.PassManager.run`
+    may use more or less parallel processes than in previous releases. If you'd like to adjust the
+    number of processes used you can use the ``QISKIT_NUM_PROCS`` environment variable or
+    ``num_processes`` field in a user configuration file (see the
+    `local configuration guide <https://docs.quantum.ibm.com/start/configure-qiskit-local>`__
+    for more details) if you need to adjust the number of processes that Qiskit potentially uses.

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

@@ -14,18 +14,54 @@
 
 from unittest import mock
 
-from qiskit.utils.multiprocessing import local_hardware_info
+from qiskit.utils import multiprocessing
 from qiskit.test import QiskitTestCase
 
 
 class TestUtil(QiskitTestCase):
     """Tests for qiskit/_util.py"""
 
-    @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):
+    def test_local_hardware_five_cpu_count(self):
+        """Test cpu count is half when sched affinity is 5"""
+        with mock.patch.object(multiprocessing, "os"):
+            multiprocessing.os.sched_getaffinity = mock.MagicMock(return_value=set(range(5)))
+            result = multiprocessing.local_hardware_info()
+        self.assertEqual(2, result["cpus"])
+
+    def test_local_hardware_sixty_four_cpu_count(self):
+        """Test cpu count is 32 when sched affinity is 64"""
+        with mock.patch.object(multiprocessing, "os"):
+            multiprocessing.os.sched_getaffinity = mock.MagicMock(return_value=set(range(64)))
+            result = multiprocessing.local_hardware_info()
+        self.assertEqual(32, result["cpus"])
+
+    def test_local_hardware_no_cpu_count(self):
         """Test cpu count fallback to 1 when true value can't be determined"""
-        del cpu_count_mock, vmem_mock, platform_mock  # unused
-        result = local_hardware_info()
+        with mock.patch.object(multiprocessing, "os"):
+            multiprocessing.os.sched_getaffinity = mock.MagicMock(return_value=set())
+            result = multiprocessing.local_hardware_info()
+        self.assertEqual(1, result["cpus"])
+
+    def test_local_hardware_no_sched_five_count(self):
+        """Test cpu cound if sched affinity method is missing and cpu count is 5."""
+        with mock.patch.object(multiprocessing, "os", spec=[]):
+            multiprocessing.os.cpu_count = mock.MagicMock(return_value=5)
+            del multiprocessing.os.sched_getaffinity
+            result = multiprocessing.local_hardware_info()
+        self.assertEqual(2, result["cpus"])
+
+    def test_local_hardware_no_sched_sixty_four_count(self):
+        """Test cpu cound if sched affinity method is missing and cpu count is 64."""
+        with mock.patch.object(multiprocessing, "os", spec=[]):
+            multiprocessing.os.cpu_count = mock.MagicMock(return_value=64)
+            del multiprocessing.os.sched_getaffinity
+            result = multiprocessing.local_hardware_info()
+        self.assertEqual(32, result["cpus"])
+
+    def test_local_hardware_no_sched_no_count(self):
+        """Test cpu count fallback to 1 when no sched getaffinity available."""
+        with mock.patch.object(multiprocessing, "os", spec=[]):
+            multiprocessing.os.cpu_count = mock.MagicMock(return_value=None)
+            del multiprocessing.os.sched_getaffinity
+            result = multiprocessing.local_hardware_info()
         self.assertEqual(1, result["cpus"])

test/python/transpiler/test_mappers.py

@@ -295,7 +295,7 @@ class TestsSabreSwap(SwapperCommonTestCases, QiskitTestCase):
     """Test SwapperCommonTestCases using SabreSwap."""
 
     pass_class = SabreSwap
-    additional_args = {"seed": 1242}
+    additional_args = {"seed": 1242, "trials": 2}
 
 
 if __name__ == "__main__":