# JuMP writeMPS does not finish writing LP model to file

**URL:** <https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427>\
**Category:** Optimization (Mathematical)\
**Created:** [May 21, 2022, 6:29pm UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427 "2022-05-21T18:29:12Z")\
**Posts on this page:** 20\
**Page:** 1

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 21, 2022, 6:29pm UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/1 "2022-05-21T18:29:12Z")

</div>

I’m trying to save a large linear program model created with JuMP v0.18.5 in Julia v0.6.4 to a .mps file on disk using writeMPS, but the file maxes out quickly at 711MB and the Julia script trying to write the file eventually is killed. I tried it three times, to verify that the file maxes out at the same number. ‘ulimit -a’ says that the maximum file size is unlimited. The operating system is Ubuntu Linux 18.04.4 LTS (bionic), 64 bit. Do you know what is causing this?

$ ulimit -a  
core file size (blocks, -c) 0  
data seg size (kbytes, -d) unlimited  
scheduling priority (-e) 0  
file size (blocks, -f) unlimited  
pending signals (-i) 127958  
max locked memory (kbytes, -l) 16384  
max memory size (kbytes, -m) unlimited  
open files (-n) 1024  
pipe size (512 bytes, -p) 8  
POSIX message queues (bytes, -q) 819200  
real-time priority (-r) 0  
stack size (kbytes, -s) unlimited  
cpu time (seconds, -t) unlimited  
max user processes (-u) 127958  
virtual memory (kbytes, -v) unlimited  
file locks (-x) unlimited

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [May 22, 2022, 12:03am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/2 "2022-05-22T00:03:25Z")

</div>

> JuMP v0.18.5 in Julia v0.6.4

Now there’s something I haven’t seen in a while! I don’t have any idea why that might happen, or suggestions for how you could debug or fix. JuMP 0.18 and Julia 0.6 are unsupported. I suggest you update to JuMP 1.0 and Julia 1.6.

You might run into a few problems doing so though, because a lot has changed since then (JuMP 0.18.5 was released in 2018). However, the benefit of updating is that you get compatibility guarantees of JuMP and Julia being 1.0 releases, so the code you write from now on won’t break in future.

On the Julia front, you might want to first install Julia 0.7, [Julia Downloads (Old releases)](https://julialang.org/downloads/oldreleases/#v070_aug_8_2018), which includes some deprecation warnings between Julia 0.6 and Julia 1.0. Fix those and then changing from 0.7 to 1.6 should be pretty simple.

On the JuMP front … a lot has changed. In fact so much that I don’t have many good suggestions for how to update. Here’s our documentation: [Introduction · JuMP](https://jump.dev/JuMP.jl/stable/)

If you have places where you get stuck, post them here and we can point you in the right direction.

---

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 22, 2022, 4:54am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/3 "2022-05-22T04:54:41Z")

</div>

This constraint causes writeMPS to hang after writing 711MB: @constraint(m,[i=1:I,j=J\_i[i]],0 \<= y[j] - x[i,j])

If I remove that constraint, writeMPS completes successfully.

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [May 22, 2022, 5:44am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/4 "2022-05-22T05:44:35Z")

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Here’s the code:

> <https://github.com/jump-dev/JuMP.jl/blob/a9de4d0de1b34b85d35c3624bea236afec7e5bec/src/writers.jl#L9-L176>

If you can provide a reproducible example, we might be able to help. But you should really update. Lots has changed (for the better):

- [JuMP 1.0.0 is released | JuMP](https://jump.dev/blog/1.0.0-release/)
- [Release notes · JuMP](https://jump.dev/JuMP.jl/latest/release_notes/#Version-1.0.0-(March-24,-2022))

In particular, we complete revamped how we do file writing, so this is likely fixed on more recent versions of JuMP.

---

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 22, 2022, 4:26pm UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/5 "2022-05-22T16:26:34Z")

</div>

Below is the code that creates the LP model and writes it to an MPS file. I should be 14888 and J is 5284. For 1 \<= i \<= I, J\_i[i] is a subset of {1,2,…,J}. c is a matrix of non-negative weights. p is a fixed positive integer like 12. If I = 14888, writeMPS hangs after writing 711MB to the file. If I is small like 500, then it works fine. I don’t know how big I can be before it breaks.

m = Model()  
@variable(m,x[i=1:I,j=J\_i[i]] \>= 0)  
@variable(m,1 \>= y[j=1:J] \>= 0)  
@objective(m,Min,sum(c[i,j]\*x[i,j] for i=1:I, j=J\_i[i]))  
@constraint(m,sum\_x[i=1:I],sum(x[i,j] for j=J\_i[i]) == 1)  
@constraint(m,sum(y[j] for j=1:J) == p)  
@constraint(m,[i=1:I,j=J\_i[i]],0 \<= y[j] - x[i,j])  
writeMPS(m,“raven5.mps”)

---

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [May 22, 2022, 8:40pm UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/6 "2022-05-22T20:40:08Z")

</div>

I don’t have any ideas for why it might hang after 711 MB of writing. You should just update to JuMP 1.0.

For your code above, the only change between JuMP 0.18 and JuMP 1.0 is:

```julia
# writeMPS(m,“raven5.mps”)
write_to_file(m, "raven5.mps")

```

But if you’re using a solver, lots of things changed, so

```julia
m = Model(solver = GurobiSolver())

```

is now

```julia
m = Model(Gurobi.Optimizer)

```

and how we solve the model and deal with statuses and solutions has changed.

```julia
status = solve(model)
x_val = getvalue(x)

```

is now

```julia
optimize!(model)
status = termination_status(model)
x_val = value.(x)

```

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 22, 2022, 9:01pm UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/7 "2022-05-22T21:01:12Z")

</div>

Could the file writing issue be related to the max locked memory, which is 16384, as shown in my initial message?

Right now, I just need the MPS file so that I can try to solve it with a third-party LP solver like PDLP in Google OR-Tools. Before creating the model with JuMP, I also need to read in the inputs from a .jld file created with JLD v0.8.3 in Julia 0.6.4.

I,J,J\_i,cost\_mat = load(“…/output\_files/bso\_data\_in\_syn\_cplex1210\_model\_11\_all.jld”,“I”,“J”,“J\_i”,“cost\_mat”)

---

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 23, 2022, 3:21am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/8 "2022-05-23T03:21:21Z")

</div>

I installed Julia v1.7.2. The script is still eventually killed when write\_to\_file is called. 621MB are written to the MPS file. write\_to\_file works fine if I is small enough.

---

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [May 23, 2022, 3:38am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/9 "2022-05-23T03:38:11Z")

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> I installed Julia v1.7.2

Okay, now that’s interesting.

What is `versioninfo()`? Is this on a laptop or some server?

What happens if you just try to write to a file normally? How far can you scale `N` in these settings?

```Julia
function main(io, N)
    for n in 1:N
        println("A B $n")
    end
end

io = IOBuffer()
main(io, 1_000_000)

open("tmp.txt", "w") do io
    main(io, 1_000_000)
end

```

---

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 23, 2022, 3:58am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/10 "2022-05-23T03:58:25Z")

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> versioninfo()  
> Julia Version 1.7.2  
> Commit bf53498635 (2022-02-06 15:21 UTC)  
> Platform Info:  
> OS: Linux (x86\_64-pc-linux-gnu)  
> CPU: Intel(R) Core™ i7-3930K CPU @ 3.20GHz  
> WORD\_SIZE: 64  
> LIBM: libopenlibm  
> LLVM: libLLVM-12.0.1 (ORCJIT, sandybridge)

This is running on a desktop server. If I run your test script, output is written to the console. The last output is: “A B 1000000”. However, nothing is written to tmp.txt.  
$ ls -alh tmp.txt  
-rw------- 1 0 May 22 22:52 tmp.txt

---

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [May 23, 2022, 4:14am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/11 "2022-05-23T04:14:49Z")

</div>

> [@odow](#):
>
> `println("A B $n")`

Oops. It should be `println(io, "A B $n")`

---

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 23, 2022, 4:27am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/12 "2022-05-23T04:27:54Z")

</div>

This time no output is written to the console, but tmp.txt is written to.

-rw------- 1 11M May 22 23:25 tmp.txt

$ tail tmp.txt  
A B 999991  
A B 999992  
A B 999993  
A B 999994  
A B 999995  
A B 999996  
A B 999997  
A B 999998  
A B 999999  
A B 1000000

---

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [May 23, 2022, 4:34am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/13 "2022-05-23T04:34:29Z")

</div>

> This time no output is written to the console, but tmp.txt is written to

And what happens as you increase `N`? `10_000_000`? `100_000_000`, `200_000_000`?

To make longer lines, you could also try

```julia
println(io, "A B $(rand() * n)")

```

I’m trying to figure out if this is a problem in JuMP’s `write_to_file` (in which case, we will fix), or a more general problem with writing on your machine, in which case, you should contact your administrator. There’s probably some setting, but I wouldn’t know where to start.

---

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 23, 2022, 5:22am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/14 "2022-05-23T05:22:00Z")

</div>

For N = 100\_000\_000:  
$ ls -alh tmp.txt  
-rw------- 1 13G May 22 23:47 tmp.txt

---

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [May 23, 2022, 5:36am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/15 "2022-05-23T05:36:51Z")

</div>

Very weird. What if you try the LP file writer? Just use `raven5.lp` as the filename.

---

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 23, 2022, 5:47am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/16 "2022-05-23T05:47:31Z")

</div>

For N = 200\_000\_000 and using the random number output you suggested, the program is killed before writing tmp.txt.  
$ julia\_1.7.2 tprint.jl  
Killed

Below is the test code in tprint.jl:  
function main(io, N)  
for n in 1:N  
println(io,“A B $(rand() \* n)”)  
end  
end

N = 2\_000\_000\_000 # 1\_000\_000\_000  
io = IOBuffer()  
main(io, N)

open(“tmp.txt”, “w”) do io  
main(io, N)  
end

---

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 23, 2022, 5:50am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/17 "2022-05-23T05:50:06Z")

</div>

The random number output script works for N = 2\_000\_000.

$ ls -alh tmp.txt  
-rw------- 1 44M May 23 00:48 tmp.txt

---

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 23, 2022, 4:18pm UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/18 "2022-05-23T16:18:34Z")

</div>

write\_to\_file(m,“raven5.lp”) also is killed and no data is written to the .lp file.  
-rw------- 1 0 May 23 01:48 raven5.lp

---

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**Author:** ![odow](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/odow/32/28685_2.png) [@odow](https://discourse.julialang.org/u/odow)\
**Post date:** [May 25, 2022, 1:51am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/19 "2022-05-25T01:51:13Z")

</div>

> [@Stuart\_Rogers](#):
>
> For N = 200\_000\_000 and using the random number output you suggested, the program is killed before writing tmp.txt.  
> $ julia\_1.7.2 tprint.jl  
> Killed

It looks like you actually ran with `N = 2_000_000_000` did you run out of disk space?

> write\_to\_file(m,“raven5.lp”) also is killed and no data is written to the .lp file.

I don’t really understand the problem. We don’t do anything special in the MPS and LP writers. They just write to a file.

Are you running out of RAM or disk space? Can you try this on a different computer? Can you share a reproducible example with all of the data that I can run?

---

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**Author:** ![Stuart\_Rogers](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stuart_rogers/32/10694_2.png) [@Stuart\_Rogers](https://discourse.julialang.org/u/Stuart_Rogers)\
**Post date:** [May 25, 2022, 7:19am UTC](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427/20 "2022-05-25T07:19:22Z")

</div>

> [@odow](#):
>
> It looks like you actually ran with `N = 2_000_000_000` did you run out of disk space?

Yes, I meant `N = 2_000_000_000`. It didn’t get to writing the file; the tmp.txt file was not even created. I believe the process was killed while trying to write to IOBuffer.

> [@odow](#):
>
> Can you try this on a different computer?

I was able to write the MPS file successfully on Windows 10 running on a modern laptop.

[Next page](https://discourse.julialang.org/t/jump-writemps-does-not-finish-writing-lp-model-to-file/81427.md?page=2)