# Profiling in Sage¶

This page lists several methods available in Sage to measure and analyze the performances of a piece of code. For more general information on profiling, see Wikipedia article Profiling_(computer_programming).

Table of contents

## How long does it take? %time and %timeit¶

The two IPython magics `%time`

and `%timeit`

measure the time it takes to
run a command:

```
sage: %time p=random_prime(2**300)
CPU times: user 152 ms, sys: 0 ns, total: 152 ms
Wall time: 150 ms
sage: %timeit p=random_prime(2**300)
10 loops, best of 3: 62.2 ms per loop
```

Note that while `%time`

only runs the command once, `%timeit`

tries to
return a more meaningful value over several runs.

For more information see `%timeit?`

or this page.

Note that Sage provides a `timeit`

function which also runs in the Sage
notebook.

## Python-level function calls: %prun¶

With `%prun`

, you can obtain the list of all Python functions involved in a
computation, as well as the time spent on each of them:

```
sage: %prun _=random_prime(2**500)
468 function calls in 0.439 seconds
Ordered by: internal time
ncalls tottime percall cumtime percall filename:lineno(function)
32 0.438 0.014 0.438 0.014 {method 'is_prime' of 'sage.rings.integer.Integer' objects}
32 0.001 0.000 0.439 0.014 arith.py:407(is_prime)
32 0.000 0.000 0.001 0.000 random.py:175(randrange)
32 0.000 0.000 0.000 0.000 random.py:244(_randbelow)
...
```

The most time-consuming functions should appear on the top. A description of the different columns is available here.

Note

You may want to sort this list differently, e.g: use `%prun -s cumulative`

for decreasing cumulative time.

Alternatively, you can “save” this data to a `Stats`

object for
further inspection:

```
sage: %prun -r random_prime(2**500)
sage: stats_object = _
sage: stats_object.total_calls
2547
```

For more information see `%prun?`

or this page.

**Visualize the statistics:** you can obtain a more graphical output with
RunSnake and Sage’s
function `runsnake()`

:

```
sage: runsnake('random_prime(2**500)')
```

## Python-level line-by-line profiling: %lprun¶

With line_profiler and its
`%lprun`

magic, you can find out which lines of one (or many) functions are
the most time-consuming. The syntax is the following:

```
%lprun -f function1 -f function2 code_to_run
```

This will display the line-by-line analysis of `function1`

and `function2`

when `code_to_run`

is executed:

```
sage: %lprun -f random_prime random_prime(2**500)
Line # Hits Time Per Hit % Time Line Contents
==============================================================
1193 def random_prime(n, proof=None, lbound=2):
... ...
1251 # since we don't want current_randstate to get
1252 # pulled when you say "from sage.arith.all import *".
1253 1 11 11.0 0.0 from sage.misc.randstate import current_randstate
1254 1 7 7.0 0.0 from sage.structure.proof.proof import get_flag
1255 1 6 6.0 0.0 proof = get_flag(proof, "arithmetic")
1256 1 17 17.0 0.0 n = ZZ(n)
...
```

In order to install `line_profiler`

you must first run the following command:

```
[user@localhost ~] sage -pip install "line_profiler"
```

## C-level function calls: %crun¶

With `%crun`

, you can obtain the list of all C functions involved in a
computation, as well as the time spent on each of them. You will need to have
the Google performance analysis tools
installed on your system:

```
sage: %crun p=random_prime(2**500)
PROFILE: interrupts/evictions/bytes = 45/0/18344
Total: 45 samples
0 0.0% 0.0% 35 77.8% PyEval_EvalCode
0 0.0% 0.0% 35 77.8% PyEval_EvalCodeEx
0 0.0% 0.0% 35 77.8% PyEval_EvalFrameEx
0 0.0% 0.0% 35 77.8% PyObject_Call
0 0.0% 0.0% 35 77.8% PyRun_StringFlags
0 0.0% 0.0% 35 77.8% __Pyx_PyObject_Call.constprop.73
...
```

For more information on `%crun`

, see `sage.misc.gperftools`

.

## C-level line-by-line profiling: perf (Linux only)¶

If your code is written in C or in Cython, you can find out line-by-line which
are the most costly using perf (included in the Ubuntu
package `linux-tools`

).

The easiest way to use it is to run some (very long) computation in Sage, and to type in a console:

```
[user@localhost ~] sudo perf top
```

Select the entry that interests you, and press `Enter`

. The `annotate`

command will show you:

- the CPU instructions
- the source code
- the associated time

```
│ * cdef unsigned long word = (<unsigned long>1) << (v & self.radix_mod_mask)
│ * return (self.edges[place] & word) >> (v & self.radix_mod_mask) # <<<<<<<<<<<<<<
│ *
│ * cpdef bint has_arc(self, int u, int v) except -1:
│ */
│ __pyx_r = (((__pyx_v_self->edges[__pyx_v_place]) & __pyx_v_word) >> (__pyx_v_v & __pyx_v_self->radix_mod_mask));
10.88 │ movslq %esi,%rsi
6.52 │ and (%rdi,%rsi,8),%rax
12.84 │ shr %cl,%rax
```

Note

- press
`s`

to toggle source code view - press
`H`

to cycle through hottest instructions - press
`h`

for help

Alternatively, or if you have no `sudo`

privileges, you can record the statistics
of a specific process into a file `perf.data`

from its PID. Then, visualize
the result using `perf report`

:

```
[user@localhost ~] perf record -p PID
[user@localhost ~] perf report --vmlinux vmlinux
```