diff --git a/.gitignore b/.gitignore
index 7ccd516..24b4937 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,38 @@
 *.o
 *.lo
 *.d
+check
+check0
+check1
+check2
+check3
+check4
+check5
+check6
+check7
+check8
+check9
+check10
+test
+test0
+test1
+test2
+test3
+test4
+test5
+test6
+test7
+test8
+test9
+test10
+test-alt0
+test-alt1
+test-alt2
+test-alt3
+test-alt4
+test-alt5
+test-alt6
+test-alt7
+test-alt8
+test-alt9
+test-alt10
diff --git a/meta/AUTHORS b/meta/AUTHORS
index 6aef6f1..b32c3a5 100644
--- a/meta/AUTHORS
+++ b/meta/AUTHORS
@@ -1,2 +1,11 @@
 Main author:
 * Olivier Brunel <jjk@jjacky.com>
+
+Contributors:
+* VoidStar [method 2]
+* Kaz Kylheku [method 4, method 5]
+* Kim Walisch [method 6]
+* Mark Dickinson [method 6]
+* Niklas B. [method 7]
+* Jim Mischel [method 8]
+* David Howells <dhowells@redhat.com> [method 9, test-alt]
diff --git a/meta/COPYING b/meta/COPYING
index a43ea21..3ef26ce 100644
--- a/meta/COPYING
+++ b/meta/COPYING
@@ -1,339 +1,15 @@
-		    GNU GENERAL PUBLIC LICENSE
-		       Version 2, June 1991
+# ISC License
 
- Copyright (C) 1989, 1991 Free Software Foundation, Inc.
-                          675 Mass Ave, Cambridge, MA 02139, USA
- Everyone is permitted to copy and distribute verbatim copies
- of this license document, but changing it is not allowed.
+Copyright (C) 2023 Olivier Brunel
 
-			    Preamble
+Permission to use, copy, modify, and/or distribute this software for any purpose
+with or without fee is hereby granted, provided that the above copyright notice
+and this permission notice appear in all copies.
 
-  The licenses for most software are designed to take away your
-freedom to share and change it.  By contrast, the GNU General Public
-License is intended to guarantee your freedom to share and change free
-software--to make sure the software is free for all its users.  This
-General Public License applies to most of the Free Software
-Foundation's software and to any other program whose authors commit to
-using it.  (Some other Free Software Foundation software is covered by
-the GNU Library General Public License instead.)  You can apply it to
-your programs, too.
-
-  When we speak of free software, we are referring to freedom, not
-price.  Our General Public Licenses are designed to make sure that you
-have the freedom to distribute copies of free software (and charge for
-this service if you wish), that you receive source code or can get it
-if you want it, that you can change the software or use pieces of it
-in new free programs; and that you know you can do these things.
-
-  To protect your rights, we need to make restrictions that forbid
-anyone to deny you these rights or to ask you to surrender the rights.
-These restrictions translate to certain responsibilities for you if you
-distribute copies of the software, or if you modify it.
-
-  For example, if you distribute copies of such a program, whether
-gratis or for a fee, you must give the recipients all the rights that
-you have.  You must make sure that they, too, receive or can get the
-source code.  And you must show them these terms so they know their
-rights.
-
-  We protect your rights with two steps: (1) copyright the software, and
-(2) offer you this license which gives you legal permission to copy,
-distribute and/or modify the software.
-
-  Also, for each author's protection and ours, we want to make certain
-that everyone understands that there is no warranty for this free
-software.  If the software is modified by someone else and passed on, we
-want its recipients to know that what they have is not the original, so
-that any problems introduced by others will not reflect on the original
-authors' reputations.
-
-  Finally, any free program is threatened constantly by software
-patents.  We wish to avoid the danger that redistributors of a free
-program will individually obtain patent licenses, in effect making the
-program proprietary.  To prevent this, we have made it clear that any
-patent must be licensed for everyone's free use or not licensed at all.
-
-  The precise terms and conditions for copying, distribution and
-modification follow.
-
-		    GNU GENERAL PUBLIC LICENSE
-   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
-
-  0. This License applies to any program or other work which contains
-a notice placed by the copyright holder saying it may be distributed
-under the terms of this General Public License.  The "Program", below,
-refers to any such program or work, and a "work based on the Program"
-means either the Program or any derivative work under copyright law:
-that is to say, a work containing the Program or a portion of it,
-either verbatim or with modifications and/or translated into another
-language.  (Hereinafter, translation is included without limitation in
-the term "modification".)  Each licensee is addressed as "you".
-
-Activities other than copying, distribution and modification are not
-covered by this License; they are outside its scope.  The act of
-running the Program is not restricted, and the output from the Program
-is covered only if its contents constitute a work based on the
-Program (independent of having been made by running the Program).
-Whether that is true depends on what the Program does.
-
-  1. You may copy and distribute verbatim copies of the Program's
-source code as you receive it, in any medium, provided that you
-conspicuously and appropriately publish on each copy an appropriate
-copyright notice and disclaimer of warranty; keep intact all the
-notices that refer to this License and to the absence of any warranty;
-and give any other recipients of the Program a copy of this License
-along with the Program.
-
-You may charge a fee for the physical act of transferring a copy, and
-you may at your option offer warranty protection in exchange for a fee.
-
-  2. You may modify your copy or copies of the Program or any portion
-of it, thus forming a work based on the Program, and copy and
-distribute such modifications or work under the terms of Section 1
-above, provided that you also meet all of these conditions:
-
-    a) You must cause the modified files to carry prominent notices
-    stating that you changed the files and the date of any change.
-
-    b) You must cause any work that you distribute or publish, that in
-    whole or in part contains or is derived from the Program or any
-    part thereof, to be licensed as a whole at no charge to all third
-    parties under the terms of this License.
-
-    c) If the modified program normally reads commands interactively
-    when run, you must cause it, when started running for such
-    interactive use in the most ordinary way, to print or display an
-    announcement including an appropriate copyright notice and a
-    notice that there is no warranty (or else, saying that you provide
-    a warranty) and that users may redistribute the program under
-    these conditions, and telling the user how to view a copy of this
-    License.  (Exception: if the Program itself is interactive but
-    does not normally print such an announcement, your work based on
-    the Program is not required to print an announcement.)
-
-These requirements apply to the modified work as a whole.  If
-identifiable sections of that work are not derived from the Program,
-and can be reasonably considered independent and separate works in
-themselves, then this License, and its terms, do not apply to those
-sections when you distribute them as separate works.  But when you
-distribute the same sections as part of a whole which is a work based
-on the Program, the distribution of the whole must be on the terms of
-this License, whose permissions for other licensees extend to the
-entire whole, and thus to each and every part regardless of who wrote it.
-
-Thus, it is not the intent of this section to claim rights or contest
-your rights to work written entirely by you; rather, the intent is to
-exercise the right to control the distribution of derivative or
-collective works based on the Program.
-
-In addition, mere aggregation of another work not based on the Program
-with the Program (or with a work based on the Program) on a volume of
-a storage or distribution medium does not bring the other work under
-the scope of this License.
-
-  3. You may copy and distribute the Program (or a work based on it,
-under Section 2) in object code or executable form under the terms of
-Sections 1 and 2 above provided that you also do one of the following:
-
-    a) Accompany it with the complete corresponding machine-readable
-    source code, which must be distributed under the terms of Sections
-    1 and 2 above on a medium customarily used for software interchange; or,
-
-    b) Accompany it with a written offer, valid for at least three
-    years, to give any third party, for a charge no more than your
-    cost of physically performing source distribution, a complete
-    machine-readable copy of the corresponding source code, to be
-    distributed under the terms of Sections 1 and 2 above on a medium
-    customarily used for software interchange; or,
-
-    c) Accompany it with the information you received as to the offer
-    to distribute corresponding source code.  (This alternative is
-    allowed only for noncommercial distribution and only if you
-    received the program in object code or executable form with such
-    an offer, in accord with Subsection b above.)
-
-The source code for a work means the preferred form of the work for
-making modifications to it.  For an executable work, complete source
-code means all the source code for all modules it contains, plus any
-associated interface definition files, plus the scripts used to
-control compilation and installation of the executable.  However, as a
-special exception, the source code distributed need not include
-anything that is normally distributed (in either source or binary
-form) with the major components (compiler, kernel, and so on) of the
-operating system on which the executable runs, unless that component
-itself accompanies the executable.
-
-If distribution of executable or object code is made by offering
-access to copy from a designated place, then offering equivalent
-access to copy the source code from the same place counts as
-distribution of the source code, even though third parties are not
-compelled to copy the source along with the object code.
-
-  4. You may not copy, modify, sublicense, or distribute the Program
-except as expressly provided under this License.  Any attempt
-otherwise to copy, modify, sublicense or distribute the Program is
-void, and will automatically terminate your rights under this License.
-However, parties who have received copies, or rights, from you under
-this License will not have their licenses terminated so long as such
-parties remain in full compliance.
-
-  5. You are not required to accept this License, since you have not
-signed it.  However, nothing else grants you permission to modify or
-distribute the Program or its derivative works.  These actions are
-prohibited by law if you do not accept this License.  Therefore, by
-modifying or distributing the Program (or any work based on the
-Program), you indicate your acceptance of this License to do so, and
-all its terms and conditions for copying, distributing or modifying
-the Program or works based on it.
-
-  6. Each time you redistribute the Program (or any work based on the
-Program), the recipient automatically receives a license from the
-original licensor to copy, distribute or modify the Program subject to
-these terms and conditions.  You may not impose any further
-restrictions on the recipients' exercise of the rights granted herein.
-You are not responsible for enforcing compliance by third parties to
-this License.
-
-  7. If, as a consequence of a court judgment or allegation of patent
-infringement or for any other reason (not limited to patent issues),
-conditions are imposed on you (whether by court order, agreement or
-otherwise) that contradict the conditions of this License, they do not
-excuse you from the conditions of this License.  If you cannot
-distribute so as to satisfy simultaneously your obligations under this
-License and any other pertinent obligations, then as a consequence you
-may not distribute the Program at all.  For example, if a patent
-license would not permit royalty-free redistribution of the Program by
-all those who receive copies directly or indirectly through you, then
-the only way you could satisfy both it and this License would be to
-refrain entirely from distribution of the Program.
-
-If any portion of this section is held invalid or unenforceable under
-any particular circumstance, the balance of the section is intended to
-apply and the section as a whole is intended to apply in other
-circumstances.
-
-It is not the purpose of this section to induce you to infringe any
-patents or other property right claims or to contest validity of any
-such claims; this section has the sole purpose of protecting the
-integrity of the free software distribution system, which is
-implemented by public license practices.  Many people have made
-generous contributions to the wide range of software distributed
-through that system in reliance on consistent application of that
-system; it is up to the author/donor to decide if he or she is willing
-to distribute software through any other system and a licensee cannot
-impose that choice.
-
-This section is intended to make thoroughly clear what is believed to
-be a consequence of the rest of this License.
-
-  8. If the distribution and/or use of the Program is restricted in
-certain countries either by patents or by copyrighted interfaces, the
-original copyright holder who places the Program under this License
-may add an explicit geographical distribution limitation excluding
-those countries, so that distribution is permitted only in or among
-countries not thus excluded.  In such case, this License incorporates
-the limitation as if written in the body of this License.
-
-  9. The Free Software Foundation may publish revised and/or new versions
-of the General Public License from time to time.  Such new versions will
-be similar in spirit to the present version, but may differ in detail to
-address new problems or concerns.
-
-Each version is given a distinguishing version number.  If the Program
-specifies a version number of this License which applies to it and "any
-later version", you have the option of following the terms and conditions
-either of that version or of any later version published by the Free
-Software Foundation.  If the Program does not specify a version number of
-this License, you may choose any version ever published by the Free Software
-Foundation.
-
-  10. If you wish to incorporate parts of the Program into other free
-programs whose distribution conditions are different, write to the author
-to ask for permission.  For software which is copyrighted by the Free
-Software Foundation, write to the Free Software Foundation; we sometimes
-make exceptions for this.  Our decision will be guided by the two goals
-of preserving the free status of all derivatives of our free software and
-of promoting the sharing and reuse of software generally.
-
-			    NO WARRANTY
-
-  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
-FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
-OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
-PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
-OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
-MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
-TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
-PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
-REPAIR OR CORRECTION.
-
-  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
-WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
-REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
-INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
-OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
-TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
-YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
-PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
-POSSIBILITY OF SUCH DAMAGES.
-
-		     END OF TERMS AND CONDITIONS
-
-	Appendix: How to Apply These Terms to Your New Programs
-
-  If you develop a new program, and you want it to be of the greatest
-possible use to the public, the best way to achieve this is to make it
-free software which everyone can redistribute and change under these terms.
-
-  To do so, attach the following notices to the program.  It is safest
-to attach them to the start of each source file to most effectively
-convey the exclusion of warranty; and each file should have at least
-the "copyright" line and a pointer to where the full notice is found.
-
-    <one line to give the program's name and a brief idea of what it does.>
-    Copyright (C) 19yy  <name of author>
-
-    This program is free software; you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
-
-Also add information on how to contact you by electronic and paper mail.
-
-If the program is interactive, make it output a short notice like this
-when it starts in an interactive mode:
-
-    Gnomovision version 69, Copyright (C) 19yy name of author
-    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
-    This is free software, and you are welcome to redistribute it
-    under certain conditions; type `show c' for details.
-
-The hypothetical commands `show w' and `show c' should show the appropriate
-parts of the General Public License.  Of course, the commands you use may
-be called something other than `show w' and `show c'; they could even be
-mouse-clicks or menu items--whatever suits your program.
-
-You should also get your employer (if you work as a programmer) or your
-school, if any, to sign a "copyright disclaimer" for the program, if
-necessary.  Here is a sample; alter the names:
-
-  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
-  `Gnomovision' (which makes passes at compilers) written by James Hacker.
-
-  <signature of Ty Coon>, 1 April 1989
-  Ty Coon, President of Vice
-
-This General Public License does not permit incorporating your program into
-proprietary programs.  If your program is a subroutine library, you may
-consider it more useful to permit linking proprietary applications with the
-library.  If this is what you want to do, use the GNU Library General
-Public License instead of this License.
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+THIS SOFTWARE.
diff --git a/meta/LICENSE b/meta/LICENSE
index f867b90..272cd42 100644
--- a/meta/LICENSE
+++ b/meta/LICENSE
@@ -1,15 +1,2 @@
-Released under GPL-2.0, see COPYING for more.
+Released under ISC, see COPYING for more.
 Copyright (C) 2023 Olivier Brunel
-
-This program is free software; you can redistribute it and/or
-modify it under the terms of the GNU General Public License
-version 2, as published by the Free Software Foundation.
-
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License
-along with this program; if not, write to the Free Software
-Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
diff --git a/meta/code b/meta/code
index b2c0c07..9b9b216 100644
--- a/meta/code
+++ b/meta/code
@@ -1 +1 @@
-https://lila.oss/code/test
+https://lila.oss/code/test-msb
diff --git a/meta/deps-bin b/meta/deps-bin
new file mode 100644
index 0000000..63eaea8
--- /dev/null
+++ b/meta/deps-bin
@@ -0,0 +1,33 @@
+test0: src/test.o src/m0.o
+test1: src/test.o src/m1.o
+test2: src/test.o src/m2.o
+test3: src/test.o src/m3.o
+test4: src/test.o src/m4.o
+test5: src/test.o src/m5.o
+test6: src/test.o src/m6.o
+test7: src/test.o src/m7.o
+test8: src/test.o src/m8.o
+test9: src/test.o src/m9.o
+test10: src/test.o src/m10.o
+test-alt0: src/test-alt.o src/m0.o
+test-alt1: src/test-alt.o src/m1.o
+test-alt2: src/test-alt.o src/m2.o
+test-alt3: src/test-alt.o src/m3.o
+test-alt4: src/test-alt.o src/m4.o
+test-alt5: src/test-alt.o src/m5.o
+test-alt6: src/test-alt.o src/m6.o
+test-alt7: src/test-alt.o src/m7.o
+test-alt8: src/test-alt.o src/m8.o
+test-alt9: src/test-alt.o src/m9.o
+test-alt10: src/test-alt.o src/m10.o
+check0: src/check.o src/m0.o
+check1: src/check.o src/m1.o
+check2: src/check.o src/m2.o
+check3: src/check.o src/m3.o
+check4: src/check.o src/m4.o
+check5: src/check.o src/m5.o
+check6: src/check.o src/m6.o
+check7: src/check.o src/m7.o
+check8: src/check.o src/m8.o
+check9: src/check.o src/m9.o
+check10: src/check.o src/m10.o
diff --git a/meta/desc b/meta/desc
new file mode 100644
index 0000000..42f29ec
--- /dev/null
+++ b/meta/desc
@@ -0,0 +1,4 @@
+Tests of different methods to find the first bit set (MSB)
+
+Testing of different methods to find the first bit set - or most significant bit
+- to see which is fastest.
diff --git a/meta/doc b/meta/doc
deleted file mode 100644
index d6b75cd..0000000
--- a/meta/doc
+++ /dev/null
@@ -1 +0,0 @@
-https://lila.oss/doc/test
diff --git a/meta/git b/meta/git
index 4bbf44f..7dbc6f1 100644
--- a/meta/git
+++ b/meta/git
@@ -1 +1 @@
-git://lila.oss/test.git
+git://lila.oss/test-msb.git
diff --git a/meta/site b/meta/site
deleted file mode 100644
index 68a3318..0000000
--- a/meta/site
+++ /dev/null
@@ -1 +0,0 @@
-https://lila.oss/test
diff --git a/project.mk b/project.mk
index 0892fd9..b080fe4 100644
--- a/project.mk
+++ b/project.mk
@@ -1,7 +1,20 @@
-$(error You need to edit project.mk)
 
 # binaries: -- don't forget to set meta/deps-bin with all deps & .o files
-BINS = 
+BINS  = test0 test1 test2 test3 test4 test5 test6 test7 test8 test9 test10
+BINS += test-alt0 test-alt1 test-alt2 test-alt3 test-alt4 test-alt5 \
+		test-alt6 test-alt7 test-alt8 test-alt9 test-alt10
+BINS += check0 check1 check2 check3 check4 check5 check6 check7 check8 \
+		check9 check10
 
-# librairies -- don't forget to set meta/deps-lib with all deps & .o files
-LIBS = 
+SCRIPTS = check test
+
+check: scripts/check
+
+test: scripts/test
+
+CLEAN += $(SCRIPTS)
+
+all: $(SCRIPTS)
+
+$(SCRIPTS):
+	$(_CP) cp scripts/$@ $@
diff --git a/scripts/check b/scripts/check
new file mode 100755
index 0000000..91cdf67
--- /dev/null
+++ b/scripts/check
@@ -0,0 +1,10 @@
+#!/bin/sh
+
+i=0
+while test $i -lt 11; do
+    ./check$i
+    e=$?
+    if test $e -ne 0; then echo "method $i: $e errors found"; fi
+    i=$(($i+1))
+done
+echo "done."
diff --git a/scripts/test b/scripts/test
new file mode 100755
index 0000000..b44203d
--- /dev/null
+++ b/scripts/test
@@ -0,0 +1,27 @@
+#!/bin/sh
+
+if test $# -ne 1 || test $1 == "tst"; then
+    echo "## Tests"
+    echo
+    i=0
+    while test $i -lt 11; do
+        printf '``` method-'$i
+        time ./test$i
+        echo '```'
+        echo
+        i=$(($i+1))
+    done
+fi
+
+if test $# -ne 1 || test $1 == "alt"; then
+    echo "## Alternative Tests"
+    echo
+    i=0
+    while test $i -lt 11; do
+        printf '``` method-'$i
+        time ./test-alt$i
+        echo '```'
+        echo
+        i=$(($i+1))
+    done
+fi
diff --git a/src/check.c b/src/check.c
new file mode 100644
index 0000000..5ae1443
--- /dev/null
+++ b/src/check.c
@@ -0,0 +1,34 @@
+#include <stdint.h>
+#include <stdio.h>
+
+typedef uint64_t u64;
+
+extern int msb(u64 v);
+
+int main(void)
+{
+    int rc = 0;
+
+    for(int n = 0; n < 64; ++n) {
+        u64 v = 1ULL << n;
+        int r = msb(v - 1);
+        if (r != n) {
+            ++rc;
+            printf("ERROR: msb(%zu)=%d [expected:%d]\n", v - 1, r, n);
+        }
+        r = msb(v);
+        if (r != n + 1) {
+            ++rc;
+            printf("ERROR: msb(%zu)=%d [expected:%d]\n", v, r, n + 1);
+        }
+        if (v + 1 != 2) {
+            r = msb(v + 1);
+            if (r != n + 1) {
+                ++rc;
+                printf("ERROR: msb(%zu)=%d [expected:%d]\n", v + 1, r, n + 1);
+            }
+        }
+    }
+
+    return rc;
+}
diff --git a/src/m0.c b/src/m0.c
new file mode 100644
index 0000000..e0bd2e8
--- /dev/null
+++ b/src/m0.c
@@ -0,0 +1,13 @@
+#include <stdint.h>
+
+typedef uint64_t u64;
+
+int msb(u64 v)
+{
+    if (!v) return 0;
+
+    int n;
+    for(n = 0; v >>= 1; ++n)
+        ;
+    return n + 1;
+}
diff --git a/src/m1.c b/src/m1.c
new file mode 100644
index 0000000..6d49569
--- /dev/null
+++ b/src/m1.c
@@ -0,0 +1,18 @@
+#include <stdint.h>
+
+typedef uint64_t u64;
+
+int msb(u64 v)
+{
+    if (!v) return 0;
+
+    int k = 0;
+    if (v > 0xFFFFFFFFUL) { v >>= 32; k  = 32; }
+    if (v > 0x0000FFFFUL) { v >>= 16; k |= 16; }
+    if (v > 0x000000FFUL) { v >>= 8;  k |= 8;  }
+    if (v > 0x0000000FUL) { v >>= 4;  k |= 4;  }
+    if (v > 0x00000003UL) { v >>= 2;  k |= 2;  }
+    if (v > 0x00000001UL) { k |= 1; }
+
+    return k + 1;
+}
diff --git a/src/m10.c b/src/m10.c
new file mode 100644
index 0000000..48cb729
--- /dev/null
+++ b/src/m10.c
@@ -0,0 +1,9 @@
+#include <stdint.h>
+
+typedef uint64_t u64;
+
+int msb(u64 v)
+{
+    if (!v) return 0;
+    return 64 - __builtin_clzll(v);
+}
diff --git a/src/m2.c b/src/m2.c
new file mode 100644
index 0000000..85433ba
--- /dev/null
+++ b/src/m2.c
@@ -0,0 +1,31 @@
+#include <stdint.h>
+
+typedef uint8_t  u8;
+typedef uint64_t u64;
+
+/* VoidStar */
+
+const u8 kTableLog2[256] = {
+0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
+5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
+6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
+7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
+7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
+};
+
+int msb(u64 v)
+{
+    if (!v) return 0;
+
+    int  k = 0;
+    if (v > 0xFFFFFFFFUL) { v >>= 32; k  = 32; }
+    if (v > 0x00FFFFFFUL) { v >>= 24; k |= 24; }
+    if (v > 0x0000FFFFUL) { v >>= 16; k |= 16; }
+    if (v > 0x000000FFUL) { v >>=  8; k |=  8; }
+    k |= kTableLog2[v]; /* precompute the Log2 of the low byte */
+
+    return k + 1;
+}
diff --git a/src/m3.c b/src/m3.c
new file mode 100644
index 0000000..53efbc7
--- /dev/null
+++ b/src/m3.c
@@ -0,0 +1,23 @@
+#include <stdint.h>
+
+typedef uint64_t u64;
+
+int msb(u64 v)
+{
+    if (!v) return 0;
+
+    u64 msb  = 32;
+    u64 step = msb;
+    while (step > 1)
+    {
+        step /= 2;
+        if (v >> msb)
+            msb += step;
+        else
+            msb -= step;
+    }
+    if (v >> msb)
+        ++msb;
+
+    return msb;
+}
diff --git a/src/m4.c b/src/m4.c
new file mode 100644
index 0000000..cabd6b4
--- /dev/null
+++ b/src/m4.c
@@ -0,0 +1,34 @@
+#include <stdint.h>
+
+typedef uint64_t u64;
+
+/* Kaz Kylheku */
+
+int msb(u64 v)
+{
+  const long long mask[] = {
+    0x00000000FFFFFFFF,
+    0x000000000000FFFF,
+    0x00000000000000FF,
+    0x000000000000000F,
+    0x0000000000000003,
+    0x0000000000000001
+  };
+  int hi = 64;
+  int lo = 0;
+  int i = 0;
+
+  if (v == 0)
+    return 0;
+
+  for (i = 0; i < sizeof mask / sizeof mask[0]; i++) {
+    int mi = lo + (hi - lo) / 2;
+
+    if ((v >> mi) != 0)
+      lo = mi;
+    else if ((v & (mask[i] << lo)) != 0)
+      hi = mi;
+  }
+
+  return lo + 1;
+}
diff --git a/src/m5.c b/src/m5.c
new file mode 100644
index 0000000..c969a95
--- /dev/null
+++ b/src/m5.c
@@ -0,0 +1,118 @@
+#include <stdint.h>
+
+typedef uint64_t u64;
+
+/* Kaz Kylheku */
+
+int msb(u64 n)
+{
+    if (n & 0xFFFFFFFF00000000) {
+        if (n & 0xFFFF000000000000) {
+            if (n & 0xFF00000000000000) {
+                if (n & 0xF000000000000000) {
+                    if (n & 0xC000000000000000)
+                        return (n & 0x8000000000000000) ? 64 : 63;
+                    else
+                        return (n & 0x2000000000000000) ? 62 : 61;
+                } else {
+                    if (n & 0x0C00000000000000)
+                        return (n & 0x0800000000000000) ? 60 : 59;
+                    else
+                        return (n & 0x0200000000000000) ? 58 : 57;
+                }
+            } else {
+                if (n & 0x00F0000000000000) {
+                    if (n & 0x00C0000000000000)
+                        return (n & 0x0080000000000000) ? 56 : 55;
+                    else
+                        return (n & 0x0020000000000000) ? 54 : 53;
+                } else {
+                    if (n & 0x000C000000000000)
+                        return (n & 0x0008000000000000) ? 52 : 51;
+                    else
+                        return (n & 0x0002000000000000) ? 50 : 49;
+                }
+            }
+        } else {
+            if (n & 0x0000FF0000000000) {
+                if (n & 0x0000F00000000000) {
+                    if (n & 0x0000C00000000000)
+                        return (n & 0x0000800000000000) ? 48 : 47;
+                    else
+                        return (n & 0x0000200000000000) ? 46 : 45;
+                } else {
+                    if (n & 0x00000C0000000000)
+                        return (n & 0x0000080000000000) ? 44 : 43;
+                    else
+                        return (n & 0x0000020000000000) ? 42 : 41;
+                }
+            } else {
+                if (n & 0x000000F000000000) {
+                    if (n & 0x000000C000000000)
+                        return (n & 0x0000008000000000) ? 40 : 39;
+                    else
+                        return (n & 0x0000002000000000) ? 38 : 37;
+                } else {
+                    if (n & 0x0000000C00000000)
+                        return (n & 0x0000000800000000) ? 36 : 35;
+                    else
+                        return (n & 0x0000000200000000) ? 34 : 33;
+                }
+            }
+        }
+    } else {
+        if (n & 0x00000000FFFF0000) {
+            if (n & 0x00000000FF000000) {
+                if (n & 0x00000000F0000000) {
+                    if (n & 0x00000000C0000000)
+                        return (n & 0x0000000080000000) ? 32 : 31;
+                    else
+                        return (n & 0x0000000020000000) ? 30 : 29;
+                } else {
+                    if (n & 0x000000000C000000)
+                        return (n & 0x0000000008000000) ? 28 : 27;
+                    else
+                        return (n & 0x0000000002000000) ? 26 : 25;
+                }
+            } else {
+                if (n & 0x0000000000F00000) {
+                    if (n & 0x0000000000C00000)
+                        return (n & 0x0000000000800000) ? 24 : 23;
+                    else
+                        return (n & 0x0000000000200000) ? 22 : 21;
+                } else {
+                    if (n & 0x00000000000C0000)
+                        return (n & 0x0000000000080000) ? 20 : 19;
+                    else
+                        return (n & 0x0000000000020000) ? 18 : 17;
+                }
+            }
+        } else {
+            if (n & 0x000000000000FF00) {
+                if (n & 0x000000000000F000) {
+                    if (n & 0x000000000000C000)
+                        return (n & 0x0000000000008000) ? 16 : 15;
+                    else
+                        return (n & 0x0000000000002000) ? 14 : 13;
+                } else {
+                    if (n & 0x0000000000000C00)
+                        return (n & 0x0000000000000800) ? 12 : 11;
+                    else
+                        return (n & 0x0000000000000200) ? 10 : 9;
+                }
+            } else {
+                if (n & 0x00000000000000F0) {
+                    if (n & 0x00000000000000C0)
+                        return (n & 0x0000000000000080) ? 8 : 7;
+                    else
+                        return (n & 0x0000000000000020) ? 6 : 5;
+                } else {
+                    if (n & 0x000000000000000C)
+                        return (n & 0x0000000000000008) ? 4 : 3;
+                    else
+                        return (n & 0x0000000000000002) ? 2 : (n ? 1 : 0);
+                }
+            }
+        }
+    }
+}
diff --git a/src/m6.c b/src/m6.c
new file mode 100644
index 0000000..2ade11e
--- /dev/null
+++ b/src/m6.c
@@ -0,0 +1,35 @@
+#include <stdint.h>
+
+typedef uint8_t  u8;
+typedef uint64_t u64;
+
+/* Kim Walisch, Mark Dickinson
+ * https://www.chessprogramming.org/BitScan#De_Bruijn_Multiplication_2
+ */
+
+const u8 index64[64] = {
+    0, 47,  1, 56, 48, 27,  2, 60,
+    57, 49, 41, 37, 28, 16,  3, 61,
+    54, 58, 35, 52, 50, 42, 21, 44,
+    38, 32, 29, 23, 17, 11,  4, 62,
+    46, 55, 26, 59, 40, 36, 15, 53,
+    34, 51, 20, 43, 31, 22, 10, 45,
+    25, 39, 14, 33, 19, 30,  9, 24,
+    13, 18,  8, 12,  7,  6,  5, 63
+};
+
+int msb(u64 v)
+{
+    if (!v) return 0;
+
+    const u64 debruijn64 = 0x03F79D71B4CB0A89UL;
+
+    v |= v >> 1;
+    v |= v >> 2;
+    v |= v >> 4;
+    v |= v >> 8;
+    v |= v >> 16;
+    v |= v >> 32;
+
+    return index64[(v * debruijn64) >> 58] + 1;
+}
diff --git a/src/m7.c b/src/m7.c
new file mode 100644
index 0000000..d289a6c
--- /dev/null
+++ b/src/m7.c
@@ -0,0 +1,38 @@
+#include <stdint.h>
+
+typedef uint8_t  u8;
+typedef uint64_t u64;
+
+/* Niklas B.
+ * https://stackoverflow.com/questions/21888140/de-bruijn-algorithm-binary-digit-count-64bits-c-sharp/21888542#21888542
+ */
+
+const u8 bitPatternToLog2[128] = {
+     0, 48, -1, -1, 31, -1, 15, 51,
+    -1, 63,  5, -1, -1, -1, 19, -1,
+    23, 28, -1, -1, -1, 40, 36, 46,
+    -1, 13, -1, -1, -1, 34, -1, 58,
+    -1, 60,  2, 43, 55, -1, -1, -1,
+    50, 62,  4, -1, 18, 27, -1, 39,
+    45, -1, -1, 33, 57, -1,  1, 54,
+    -1, 49, -1, 17, -1, -1, 32, -1,
+    53, -1, 16, -1, -1, 52, -1, -1,
+    -1, 64,  6,  7,  8, -1,  9, -1,
+    -1, -1, 20, 10, -1, -1, 24, -1,
+    29, -1, -1, 21, -1, 11, -1, -1,
+    41, -1, 25, 37, -1, 47, -1, 30,
+    14, -1, -1, -1, -1, 22, -1, -1,
+    35, 12, -1, -1, -1, 59, 42, -1,
+    -1, 61,  3, 26, 38, 44, -1, 56
+};
+
+int msb(u64 v)
+{
+    v |= v >> 1;
+    v |= v >> 2;
+    v |= v >> 4;
+    v |= v >> 8;
+    v |= v >> 16;
+    v |= v >> 32;
+    return bitPatternToLog2[(u64)(v * 0x6C04F118E9966F6BUL) >> 57];
+}
diff --git a/src/m8.c b/src/m8.c
new file mode 100644
index 0000000..b75e08c
--- /dev/null
+++ b/src/m8.c
@@ -0,0 +1,38 @@
+#include <stdint.h>
+
+typedef uint8_t  u8;
+typedef uint32_t u32;
+typedef uint64_t u64;
+
+/* de Bruijn magic & table from Jim Mischel */
+
+const u8 table[32] =
+{
+     0,  9,  1, 10, 13, 21,  2, 29,
+    11, 14, 16, 18, 22, 25,  3, 30,
+     8, 12, 20, 28, 15, 17, 24,  7,
+    19, 27, 23,  6, 26,  5,  4, 31
+};
+
+int msb(u64 v)
+{
+    if (!v) return 0;
+
+    u32 v32;
+    u8 n;
+    if (v > 0xFFFFFFFF) {
+        v32 = v >> 32;
+        n = 33;
+    } else {
+        v32 = v;
+        n = 1;
+    }
+
+    v32 |= v32 >> 1;
+    v32 |= v32 >> 2;
+    v32 |= v32 >> 4;
+    v32 |= v32 >> 8;
+    v32 |= v32 >> 16;
+
+    return n + table[(v32 * 0x07C4ACDDU) >> 27];
+}
diff --git a/src/m9.c b/src/m9.c
new file mode 100644
index 0000000..5cf3824
--- /dev/null
+++ b/src/m9.c
@@ -0,0 +1,13 @@
+#include <stdint.h>
+
+typedef uint64_t u64;
+
+int msb(u64 v)
+{
+    long n = -1;
+
+    __asm__("bsrq %1,%0"
+        : "+r" (n)
+        : "rm" (v));
+    return n + 1;
+}
diff --git a/src/test-alt.c b/src/test-alt.c
new file mode 100644
index 0000000..ca0ccb4
--- /dev/null
+++ b/src/test-alt.c
@@ -0,0 +1,35 @@
+#include <stdint.h>
+
+typedef uint64_t u64;
+
+extern int msb(u64 v);
+
+int total = 0;
+
+/* By David Howells */
+
+#define PAGE_SHIFT 12
+static int
+get_msb(u64 v)
+{
+    int r;
+    --v;
+    v >>= PAGE_SHIFT;
+    r = msb(v);
+    return r;
+}
+
+int main(void)
+{
+    long rep, loop;
+    u64 v;
+
+    for (rep = 1000000; rep > 0; --rep) {
+        for (loop = 0; loop <= 16384; loop += 4) {
+            v = 1UL << loop;
+            total += get_msb(v);
+        }
+    }
+
+    return 0;
+}
diff --git a/src/test.c b/src/test.c
new file mode 100644
index 0000000..aa13dec
--- /dev/null
+++ b/src/test.c
@@ -0,0 +1,19 @@
+#include <stdint.h>
+
+typedef uint64_t u64;
+
+extern int msb(u64 v);
+
+int total = 0;
+
+int main(void)
+{
+    for(int i = 4200000; i > 0; --i) {
+        for(int l = 0; l < 64; ++l) {
+            u64 n = 1ULL << l;
+            total += msb(n - 1) + msb(n) + msb(n + 1);
+        }
+    }
+
+    return 0;
+}