Added solvers

src/Solvers/CG.jl

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+###
+### "THE BEER-WARE LICENSE":
+### Alberto Ramos wrote this file. As long as you retain this 
+### notice you can do whatever you want with this stuff. If we meet some 
+### day, and you think this stuff is worth it, you can buy me a beer in 
+### return. <alberto.ramos@cern.ch>
+###
+### file:    CG.jl
+### created: Tue Nov 30 11:10:57 2021
+###                               
+
+"""
+    function CG!
+
+Solves the linear equation `Ax = si`
+"""
+function CG!(si, U, m0, A, lp::SpaceParm, dws::DiracWorkspace)
+
+    dws.sr .= si
+    dws.sp .= si
+    norm = CUDA.mapreduce(x -> norm2(x), +, si)
+    fill!(si,zero(eltype(so)))
+    err = 0.0
+    
+    tol = eps * norm
+    iterations = 0
+
+    niter = 0
+    for i in 1:maxiter
+        A(dws.sAp, U, dws.sp, am0, dws.st, lp)
+        prod  = CUDA.mapreduce(x -> dot(x[1],x[2]), +, zip(dws.sp, dws.sAp))
+        alpha = norm/prod
+
+        si     .= si     .+ alpha .* dws.sp
+        dws.sr .= dws.sr .- alpha .* dws.sAp
+
+        err = CUDA.mapreduce(x -> norm2(x), +, dws.sr)
+        
+        if err < tol
+	    niter = i
+            break
+        end
+
+        beta = err/norm
+        dws.sp .= dws.sr .+ beta .* dws.sp
+        
+        norm = err;
+    end
+
+    if err > tol
+	error("CG! not converged after $maxiter iterations (Residuals: $err)")
+    end
+    
+    return niter
+end

src/Solvers/Solvers.jl

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+###
+### "THE BEER-WARE LICENSE":
+### Alberto Ramos wrote this file. As long as you retain this 
+### notice you can do whatever you want with this stuff. If we meet some 
+### day, and you think this stuff is worth it, you can buy me a beer in 
+### return. <alberto.ramos@cern.ch>
+###
+### file:    Solvers.jl
+### created: Tue Nov 30 11:09:51 2021
+###                               
+
+module Solvers
+
+using CUDA, TimerOutputs
+using ..Space
+using ..Groups
+using ..Fields
+using ..YM
+using ..Spinors
+using ..Dirac
+
+include("CG.jl")
+export CG!
+
+
+
+
+end