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Make it clearer how the user can control compiler optimization #530

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Merged
merged 7 commits into from
Sep 21, 2021
Merged

Make it clearer how the user can control compiler optimization #530

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5a9c6f6
Make it clearer how the user can control compiler optimization
gareth-nx Sep 19, 2021
6da1672
fix suggested by awvwgk
gareth-nx Sep 19, 2021
6ec8d6b
remove -fPIC from compiler flags
gareth-nx Sep 20, 2021
cbc8dd6
Mention deletion of the build folder as a strategy for recompiling
gareth-nx Sep 20, 2021
58c9b37
Enable Makefile.manual to use environmental variables for FC, FFLAGS,…
gareth-nx Sep 20, 2021
8178a1c
Remove -flto to make the example almost compiler independent
gareth-nx Sep 20, 2021
dba123d
Quotes for stdlib
gareth-nx Sep 20, 2021
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6 changes: 3 additions & 3 deletions Makefile.manual
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Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
# Fortran stdlib Makefile

FC = gfortran
FFLAGS = -Wall -Wextra -Wimplicit-interface -fPIC -g -fcheck=all
FYPPFLAGS=
FC ?= gfortran
FFLAGS ?= -Wall -Wextra -Wimplicit-interface -fPIC -g -fcheck=all
FYPPFLAGS ?=

export FC
export FFLAGS
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12 changes: 11 additions & 1 deletion README.md
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Expand Up @@ -134,9 +134,10 @@ Important options are
Compiling with maximum rank 15 can be resource intensive and requires at least 16 GB of memory to allow parallel compilation or 4 GB memory for sequential compilation.
- `-DBUILD_SHARED_LIBS` set to `on` in case you want link your application dynamically against the standard library (default: `off`).

For example, to configure a build using the Ninja backend and generating procedures up to rank 7, which is installed to your home directory use
For example, to configure a build using the Ninja backend while specifying compiler flags `FFLAGS`, generating procedures up to rank 7, and installing to your home directory, use

```sh
export FFLAGS="-O3"
cmake -B build -G Ninja -DCMAKE_MAXIMUM_RANK:String=7 -DCMAKE_INSTALL_PREFIX=$HOME/.local
```

Expand All @@ -162,6 +163,10 @@ cmake --install build

Now you have a working version of stdlib you can use for your project.

If at some point you wish to recompile `stdlib` with different options, you might
want to delete the `build` folder. This will ensure that cached variables from
earlier builds do not affect the new build.


### Build with make

Expand All @@ -177,6 +182,11 @@ You can limit the maximum rank by setting ``-DMAXRANK=<num>`` in the ``FYPPFLAGS
make -f Makefile.manual FYPPFLAGS=-DMAXRANK=4
```

You can also specify the compiler and compiler-flags by setting the ``FC`` and ``FFLAGS`` environmental variables. Among other things, this facilitates use of compiler optimizations that are not specified in the Makefile.manual defaults.
```sh
make -f Makefile.manual FYPPFLAGS=-DMAXRANK=4 FC=gfortran FFLAGS="-O3 -flto"
```

### Build with [fortran-lang/fpm](https://github.com/fortran-lang/fpm)

Fortran Package Manager (fpm) is a package manager and build system for Fortran.
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