Surface parametrization failed

[jtorresfabra]

Describe the bug
I'm experiencing a lot of surface parametrization fails (lscm mode), even with simple meshes. At the beginning I thought it was due to non-manifold meshes. But seems is also happening with manifold ones.

To Reproduce

Added a patch of a bigger mesh where the parametrization is already failing.
Just load the mesh and

pmp::SurfaceParameterization param(mesh);
param.lscm();

The error I get is:

SurfaceParameterization: Could not solve linear system

Here you have the mesh:

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v -0.7187205553 0.0072185006 -0.6963074803
v -0.7367604971 0.0071144998 -0.6924955249
v -0.7344155312 0.0081265010 -0.6661835313
v -0.7174115181 0.0070054997 -0.7214004993
v -0.7372324467 0.0062004998 -0.7174305320
v -0.6941875219 0.0069044996 -0.6741214991
v -0.6956804991 0.0083875004 -0.7014294863
v -0.6478462815 0.0043691583 -0.5512301326
v -0.6589392424 0.0047934959 -0.5512301326
v -0.6554839611 0.0046613216 -0.5512301326
v -0.6709845066 0.0052074995 -0.6796914935
v -0.6720294952 0.0064525008 -0.7061825395
v -0.6515884399 0.0051004998 -0.5662325025
v -0.6721204519 0.0068165008 -0.7349734902
v -0.6477094889 0.0047705006 -0.6854125261
v -0.6487824917 0.0062985010 -0.7109814882
v -0.6387109756 0.0040080207 -0.5512301326
v -0.6491094828 0.0071565006 -0.7308275104
v -0.6297174692 0.0044315010 -0.5712625384
v -0.6245731115 0.0042155883 -0.5512301326
v -0.6189453006 0.0038505008 -0.5512301326
v -0.5997148752 0.0024406761 -0.5512301326
v -0.7305405140 0.0059715007 -0.6389564872
v -0.6013924479 0.0025071856 -0.5512301326
v -0.7119884491 0.0064955000 -0.6418855190
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v -0.6795884967 0.0050035608 -0.5512301326
v -0.6941789985 0.0040637068 -0.5512301326
v -0.7003914118 0.0039176587 -0.5512301326
v -0.7161245346 0.0034299418 -0.5512301326
v -0.7205038667 0.0033654438 -0.5512301326
v -0.5618433952 0.0050669205 -0.7049937844
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v -0.7491245270 0.0010908043 -0.5512301326
v -0.7491245270 0.0000000000 -0.6104965210
v -0.5618433952 0.0048167096 -0.6612778306
v -0.7491245270 0.0000000000 -0.6105730534
v -0.7491245270 0.0000000000 -0.6373705268
v -0.6005444527 0.0061544999 -0.6686275005
v -0.6024965048 0.0068635009 -0.6951605082
v -0.7491245270 0.0000000000 -0.6389039159
v -0.7491245270 0.0000000000 -0.5833604932
v -0.7491245270 0.0000000000 -0.5567328334
v -0.7491245270 0.0000000000 -0.5563964844
v -0.7491245270 0.0000000000 -0.5836412311
v -0.6225805283 0.0053805001 -0.6626535058
v -0.7491245270 0.0005596421 -0.5512301326
v -0.7491245270 0.0000000000 -0.5512301326
v -0.6249915361 0.0060364995 -0.6902045012
v -0.6259135008 0.0060035009 -0.7153034806
v -0.6032265425 0.0068354998 -0.7192485332
v -0.5618433952 0.0048708180 -0.7273030281
v -0.5618433952 0.0049936040 -0.7089808583
v -0.5618433952 0.0049470384 -0.7252701521
f 1//1 2//2 3//3
f 3//3 4//4 1//1
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f 3//3 2//2 5//5
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f 2//2 1//1 7//7
f 8//8 5//5 2//2
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f 20//20 14//14 18//18
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f 1//1 4//4 24//24
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f 29//29 27//27 28//28
f 30//30 7//7 26//26
f 29//29 31//31 32//32
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f 34//34 27//27 33//33
f 12//12 7//7 30//30
f 30//30 35//35 12//12
f 36//36 37//37 38//38
f 36//36 38//38 39//39
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f 12//12 35//35 16//16
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f 35//35 42//42 16//16
f 6//6 43//43 44//44
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f 53//53 62//62 57//57
f 57//57 20//20 23//23
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f 45//45 44//44 64//64
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f 45//45 64//64 61//61
f 43//43 51//51 66//66
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f 23//23 52//52 57//57
f 51//51 69//69 70//70
f 51//51 70//70 67//67
f 51//51 15//15 71//71
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f 62//62 14//14 57//57
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f 20//20 57//57 14//14
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f 102//102 14//14 81//81
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f 15//15 107//107 74//74
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f 120//120 121//121 98//98
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f 80//80 79//79 46//46
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f 40//40 108//108 124//124
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f 109//109 124//124 110//110
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f 123//123 120//120 97//97
f 123//123 46//46 125//125
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f 127//127 109//109 119//119
f 119//119 128//128 127//127
f 127//127 50//50 40//40
f 129//129 46//46 63//63
f 46//46 129//129 126//126
f 40//40 109//109 127//127
f 120//120 130//130 131//131
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f 120//120 123//123 133//133
f 134//134 127//127 128//128
f 120//120 133//133 130//130
f 120//120 135//135 122//122
f 120//120 132//132 135//135
f 132//132 136//136 135//135
f 128//128 137//137 134//134
f 134//134 53//53 50//50
f 127//127 134//134 50//50
f 42//42 134//134 137//137
f 137//137 16//16 42//42
f 42//42 62//62 53//53
f 137//137 138//138 17//17
f 17//17 16//16 137//137
f 87//87 19//19 17//17
f 17//17 138//138 87//87
f 128//128 139//139 138//138
f 138//138 137//137 128//128
f 138//138 139//139 87//87
f 134//134 42//42 53//53
f 42//42 35//35 62//62
f 119//119 140//140 139//139
f 139//139 128//128 119//119
f 87//87 140//140 92//92
f 87//87 139//139 140//140
f 140//140 141//141 142//142
f 140//140 119//119 141//141
f 119//119 118//118 141//141

Expected behavior
Create a parametrization for the mesh.

Environment (please complete the following information):

• OS: Ubuntu 16.04
• Compiler: clang-6
• Build type: Debug/Release

[jtorresfabra]

Additional note: Same mesh with blender unwrap (which as far as I know is using lscm too) works.

[dsieger]

Looks like @mbotsch fixed as a by-product of commit ace532d

Trying your example mesh with the latest version seems to give a reasonable result, see attached.