add a new librpa module

mushroom/librpa.py

@@ -0,0 +1,39 @@
+# -*- coding: utf-8 -*-
+"""Utilities for LibRPA"""
+import numpy as np
+from io import StringIO
+
+from mushroom.core.logger import loggers
+
+_logger = loggers["librpa"]
+
+
+def read_self_energy_imagfreq(fn: str):
+    """Read self energy on imaginary frequency from data file ``fn``
+
+    Args:
+        fn (str) : path to the data file
+
+    Returns:
+        2 nd-array. The first is 1d array containing the (imaginary) frequency points.
+        The second is 4d array, (nfreq, nspin, nkpts, nstates) containing the
+        correlation self energy data
+    """
+    omegas = None
+    data = None
+
+    with open(fn, 'r') as h:
+        lines = h.readlines()
+    nfreqs, nspins, nkpts, nstates = map(int, lines[0].split())
+
+    _logger.info("Sigma dimension, nfreq, nspin, nkpsts, nstates: %d %d %d %d",
+                 nfreqs, nspins, nkpts, nstates)
+
+    omegas = np.loadtxt(StringIO("".join(lines[1:1 + nfreqs])))
+    data_re, data_im = np.loadtxt(StringIO("".join(lines[1 + nfreqs:])), unpack=True)
+    data = data_re + 1.0j * data_im
+    data = data.reshape(nspins, nkpts, nstates, nfreqs)
+    # move the nfreqs axis to the first
+    data = np.rollaxis(data, 3, 0)
+
+    return omegas, data