add a script to generate particles

benchmarks/clustering/scripts/gen_particles.py

+import os
+from pyHepMC3 import HepMC3 as hm
+import numpy as np
+import argparse
+
+
+PARTICLES = {
+    "pion0": (111, 0.1349766),       # pi0
+    "pion+": (211, 0.13957018),      # pi+
+    "pion-": (-211, 0.13957018),     # pi-
+    "kaon0": (311, 0.497648),        # K0
+    "kaon+": (321, 0.493677),        # K+
+    "kaon-": (-321, 0.493677),       # K-
+    "proton": (2212, 0.938272),      # proton
+    "neutron": (2112, 0.939565),     # neutron
+    "electron": (11, 0.51099895e-3), # electron
+    "positron": (-11, 0.51099895e-3),# positron
+    "photon": (22, 0),               # photon
+}
+
+
+def gen_event(p, theta, phi, pid, mass):
+    evt = hm.GenEvent(momentum_unit=hm.Units.MomentumUnit.GEV, length_unit=hm.Units.LengthUnit.MM)
+    # final state
+    state = 1
+    e0 = np.sqrt(p*p + mass*mass)
+    px = np.cos(phi)*np.sin(theta)
+    py = np.sin(phi)*np.sin(theta)
+    pz = np.cos(theta)
+
+    # beam
+    pbeam = hm.GenParticle(hm.FourVector(0, 0, 0, 0.938272), 2212, 4)
+    ebeam = hm.GenParticle(hm.FourVector(0, 0, e0, np.sqrt(e0*e0 + 0.511e-3*0.511e-3)), 11, 4)
+
+    # out particle
+    hout = hm.GenParticle(hm.FourVector(px*p, py*p, pz*p, e0), pid, state)
+
+    # vertex
+    vert = hm.GenVertex()
+    vert.add_particle_in(ebeam)
+    vert.add_particle_in(pbeam)
+    vert.add_particle_out(hout)
+    evt.add_vertex(vert)
+    return evt
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+
+    parser.add_argument('output', help='path to the output file')
+    parser.add_argument('-n', type=int, default=1000, dest='nev', help='number of events to generate')
+    parser.add_argument('--parray', type=str, default="", dest='parray', help='an array of momentum in GeV')
+    parser.add_argument('--pmin', type=float, default=8.0, dest='pmin', help='minimum momentum in GeV')
+    parser.add_argument('--pmax', type=float, default=100.0, dest='pmax', help='maximum momentum in GeV')
+    parser.add_argument('--angmin', type=float, default=0.0, dest='angmin', help='minimum angle in degree')
+    parser.add_argument('--angmax', type=float, default=20.0, dest='angmax', help='maximum angle in degree')
+    parser.add_argument('--phmin', type=float, default=0.0, dest='phmin', help='minimum angle in degree')
+    parser.add_argument('--phmax', type=float, default=360.0, dest='phmax', help='maximum angle in degree')
+    parser.add_argument('--particles', type=str, default='electron', dest='particles', help='particle names')
+    parser.add_argument('-s', type=int, default=-1, dest='seed', help='seed for random generator')
+
+    args = parser.parse_args()
+
+    # random seed (< 0 will get it from enviroment variable 'SEED', or a system random number)
+    if args.seed < 0:
+        args.seed = os.environ.get('SEED', int.from_bytes(os.urandom(4), byteorder='big', signed=False))
+    np.random.seed(args.seed)
+
+    output = hm.WriterAscii(args.output);
+    if output.failed():
+        print("Cannot open file \"{}\"".format(args.output))
+        sys.exit(2)
+
+    # build particle info
+    parts = []
+    for pid in args.particles.split(','):
+        pid = pid.strip()
+        if pid not in PARTICLES.keys():
+            print('pid {:d} not found in dictionary, ignored.'.format(pid))
+            continue
+        parts.append(PARTICLES[pid])
+
+    # p values
+    pvals = np.random.uniform(args.pmin, args.pmax, args.nev) if not args.parray else \
+            np.random.choice([float(p.strip()) for p in args.parray.split(',')], args.nev)
+    thvals = np.random.uniform(args.angmin, args.angmax, args.nev)/180.*np.pi
+    phivals = np.random.uniform(args.phmin, args.phmax, args.nev)/180.*np.pi
+    partvals = [parts[i] for i in np.random.choice(len(parts), args.nev)]
+
+    count = 0
+    for p, theta, phi, (pid, mass) in zip(pvals, thvals, phivals, partvals):
+        if (count % 1000 == 0):
+            print("Generated {} events".format(count), end='\r')
+        evt = gen_event(p, theta, phi, pid, mass)
+        output.write_event(evt)
+        evt.clear()
+        count += 1
+
+    print("Generated {} events".format(args.nev))
+    output.close()
+