From db2061d1b45cb7858bf77b58e26ccadf5714a7ab Mon Sep 17 00:00:00 2001
From: giannozz <giannozz@c92efa57-630b-4861-b058-cf58834340f0>
Date: Mon, 16 Oct 2017 20:41:31 +0000
Subject: [PATCH] Yet another hour wasted thanks to a misleading comment:
 previously removed variable "qnorm" was actually needed to ensure correct
 allocation (via allocate_nlpot) of variables used by EXX with USPP and PAW

git-svn-id: http://qeforge.qe-forge.org/svn/q-e/trunk/espresso@13926 c92efa57-630b-4861-b058-cf58834340f0
---
 Doc/release-notes |  7 ++++---
 PW/src/exx.f90    | 16 ++++++++++++++--
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/Doc/release-notes b/Doc/release-notes
index 6fb5bfd7e..50bc5534d 100644
--- a/Doc/release-notes
+++ b/Doc/release-notes
@@ -19,10 +19,11 @@ New in 6.2 version:
 
 Fixed in 6.2 version
 
-  * Bug in DFPT with a constrained magnetization for insulators 
+  * DFPT with constrained magnetization for insulators wasn't working
+    (r13915)
 
-  * virtual.x was linking a duplicate obsolete "pseudo" module, leading 
-    to an "unrecognized dft" error (fix provided by Stefano Dal Forno)
+  * virtual.x was linking a duplicate obsolete "pseudo" module, leading to
+    "unrecognized dft" error (fix provided by Stefano Dal Forno, r13910)
 
   * NEB + EXX works again (r13851)
 
diff --git a/PW/src/exx.f90 b/PW/src/exx.f90
index f32af6a1d..9cd854e77 100644
--- a/PW/src/exx.f90
+++ b/PW/src/exx.f90
@@ -243,13 +243,15 @@ MODULE exx
        gkcut = ecutwfc/tpiba2
        exx_fft%gcutmt = ecutfock / tpiba2
     ELSE
-       !
        !
        gkcut = 0.0_dp
        DO ik = 1,nks
           gkcut = MAX ( gkcut, sqrt( sum(xk(:,ik)**2) ) )
        ENDDO
        CALL mp_max( gkcut, inter_pool_comm )
+       ! Alternatively, variable "qnorm" earlier computed in "exx_grid_init"
+       ! could be used as follows:
+       ! gkcut = ( sqrt(ecutwfc/tpiba2) + qnorm )**2
        gkcut = ( sqrt(ecutwfc/tpiba2) + gkcut )**2
        ! 
        ! The following instruction may be needed if ecutfock \simeq ecutwfc
@@ -430,7 +432,7 @@ MODULE exx
     USE cell_base,  ONLY : bg, at
     USE spin_orb,   ONLY : domag
     USE noncollin_module, ONLY : nspin_lsda
-    USE klist,      ONLY : xk, wk, nkstot, nks
+    USE klist,      ONLY : xk, wk, nkstot, nks, qnorm
     USE wvfct,      ONLY : nbnd
     USE start_k,    ONLY : nk1,nk2,nk3
     USE control_flags, ONLY : iverbosity
@@ -640,6 +642,16 @@ MODULE exx
     CALL exx_grid_check ( xk_collect(:,:) )
     DEALLOCATE( xk_collect )
     !
+    ! qnorm = max |q|, used in allocate_nlpot to compute the maximum size
+    !         of some arrays (e.g. qrad) - beware: needed for US/PAW+EXX
+    !
+    qnorm = 0.0_dp
+    DO iq = 1,nkqs
+       DO ik = 1,nks
+          qnorm = max(qnorm, sqrt( sum((xk(:,ik)-xkq_collect(:,iq))**2) ))
+       ENDDO
+    ENDDO
+    !
     CALL stop_clock ('exx_grid')
     !
     RETURN