lock by default - add safe_lock option for control

src/ProgressMeter.jl

@@ -81,7 +81,7 @@ Base.@kwdef mutable struct ProgressCore
     numprintedvalues::Int       = 0             # num values printed below progress in last iteration
     prev_update_count::Int      = 1             # counter at last update
     printed::Bool               = false         # true if we have issued at least one status update
-    threads_used::Vector{Int}   = Int[]         # threads that have used this progress meter
+    safe_lock::Bool             = Threads.nthreads() > 1 # set to false for non-threaded tight loops
     tinit::Float64              = time()        # time meter was initialized
     tlast::Float64              = time()        # time of last update
     tsecond::Float64            = time()        # ignore the first loop given usually uncharacteristically slow
@@ -441,17 +441,8 @@ end
 
 predicted_updates_per_dt_have_passed(p::AbstractProgress) = p.counter - p.prev_update_count >= p.check_iterations
 
-function is_threading(p::AbstractProgress)
-    Threads.nthreads() == 1 && return false
-    length(p.threads_used) > 1 && return true
-    if !in(Threads.threadid(), p.threads_used)
-        push!(p.threads_used, Threads.threadid())
-    end
-    return length(p.threads_used) > 1
-end
-
 function lock_if_threading(f::Function, p::AbstractProgress)
-    if is_threading(p)
+    if p.safe_lock
         lock(p.lock) do
             f()
         end
@@ -817,7 +808,6 @@ function showprogressthreads(args...)
             length($(esc(iters)));
             $(showprogress_process_args(progressargs)...),
         )
-        append!($(esc(p)).threads_used, 1:Threads.nthreads())
         $(esc(expr))
         finish!($(esc(p)))
     end

test/core.jl

@@ -80,3 +80,19 @@ prog.n = UInt128(20) # in Progress
 @test prog.n == 20
 prog.offset = Int8(5) # in ProgressCore
 @test prog.offset == 5
+
+# Test safe_lock option, initialization and execution. 
+function simple_sum(n; safe_lock = true)
+    p = Progress(n; safe_lock)
+    s = 0.0
+    for i in 1:n
+        s += sin(i)^2
+        next!(p)
+    end
+    return s
+end
+p = Progress(10)
+@test p.safe_lock == (Threads.nthreads() > 1)
+p = Progress(10; safe_lock = false)
+@test p.safe_lock == false
+@test simple_sum(10; safe_lock = false) ≈ simple_sum(10; safe_lock = false)

test/test.jl

@@ -386,6 +386,7 @@ finish!(prog)
 
 println("Testing fractional bars")
 for front in (['▏','▎','▍','▌','▋','▊', '▉'], ['▁' ,'▂' ,'▃' ,'▄' ,'▅' ,'▆', '▇'], ['░', '▒', '▓',])
+    local p
     p = Progress(100, dt=0.01, barglyphs=BarGlyphs('|','█',front,' ','|'), barlen=10)
     for i in 1:100
         next!(p)

test/test_threads.jl

@@ -7,7 +7,6 @@
     threadsUsed = fill(false, threads)
     vals = ones(n*threads)
     p = Progress(n*threads)
-    p.threads_used = 1:threads # short-circuit the function `is_threading` because it is racy (#232)
     Threads.@threads for i = 1:(n*threads)
         threadsUsed[Threads.threadid()] = true
         vals[i] = 0
@@ -21,7 +20,6 @@
     println("Testing ProgressUnknown() with Threads.@threads across $threads threads")
     trigger = 100.0
     prog = ProgressUnknown(desc="Attempts at exceeding trigger:")
-    prog.threads_used = 1:threads
     vals = Float64[]
     threadsUsed = fill(false, threads)
     lk = ReentrantLock()
@@ -48,7 +46,6 @@
     println("Testing ProgressThresh() with Threads.@threads across $threads threads")
     thresh = 1.0
     prog = ProgressThresh(thresh; desc="Minimizing:")
-    prog.threads_used = 1:threads
     vals = fill(300.0, 1)
     threadsUsed = fill(false, threads)
     Threads.@threads for _ in 1:100000
@@ -76,7 +73,6 @@
         # threadsUsed = fill(false, threads)
         vals = ones(n*threads)
         p = Progress(n*threads)
-        p.threads_used = 1:threads
 
         for t in 1:threads
             tasks[t] = Threads.@spawn for i in 1:n