Given a symmetric matrix class="mathmlsrc">title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si10.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=b5fc379955006cd5e41053b8bbf2e721">class="imgLazyJSB inlineImage" height="17" width="113" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0166218X16302189-si10.gif">class="mathContainer hidden">class="mathCode">, an class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si11.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=1750eeba9862b1fce9a11669839235ed" title="Click to view the MathML source">Mclass="mathContainer hidden">class="mathCode">-partition of a graph class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si5.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=1247fab1fbc9a897ced99a57e517a0c5" title="Click to view the MathML source">Gclass="mathContainer hidden">class="mathCode"> is a function from class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si13.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=10c79920053c4a1d1dd04252449ce64f" title="Click to view the MathML source">V(G)class="mathContainer hidden">class="mathCode"> to class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si14.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=7029ed6b70f6acc735ffafecfc3d5222" title="Click to view the MathML source">Dclass="mathContainer hidden">class="mathCode"> such that no edge of class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si5.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=1247fab1fbc9a897ced99a57e517a0c5" title="Click to view the MathML source">Gclass="mathContainer hidden">class="mathCode"> is mapped to a class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si16.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=a78adec3682db8af4a9c58fe7d52eb66" title="Click to view the MathML source">0class="mathContainer hidden">class="mathCode"> of class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si11.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=1750eeba9862b1fce9a11669839235ed" title="Click to view the MathML source">Mclass="mathContainer hidden">class="mathCode"> and no non-edge to a class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si18.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=2642f7229c42c6d068ac7984a08628bf" title="Click to view the MathML source">1class="mathContainer hidden">class="mathCode">. We give a computer-assisted proof that, when class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si19.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=3e42b363a0e62647558ad7d16723b22f" title="Click to view the MathML source">|D|=4class="mathContainer hidden">class="mathCode">, the problem of counting the class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si11.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=1750eeba9862b1fce9a11669839235ed" title="Click to view the MathML source">Mclass="mathContainer hidden">class="mathCode">-partitions of an input graph is either in class="mathmlsrc">title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si21.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=5e373751ee3978b0e0f1b9f2a919e8df">class="imgLazyJSB inlineImage" height="11" width="17" alt="View the MathML source" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0166218X16302189-si21.gif">class="mathContainer hidden">class="mathCode"> or is class="mathmlsrc">title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si22.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=f364bcd929098ab75a9499d11566151e">class="imgLazyJSB inlineImage" height="11" width="20" alt="View the MathML source" style="margin-top: -5px; vertical-align: middle" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0166218X16302189-si22.gif">class="mathContainer hidden">class="mathCode">-complete. Tractability is proved by reduction to the related problem of counting list class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si11.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=1750eeba9862b1fce9a11669839235ed" title="Click to view the MathML source">Mclass="mathContainer hidden">class="mathCode">-partitions; intractability is shown using a gadget construction and interpolation. We use a computer program to determine which of the two cases holds for all but a small number of matrices, which we resolve manually to establish the dichotomy. We conjecture that the dichotomy also holds for class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si24.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=1087eaaba3bd04294448660712d87fa9" title="Click to view the MathML source">|D|>4class="mathContainer hidden">class="mathCode">. More specifically, we conjecture that, for any symmetric matrix class="mathmlsrc">title="View the MathML source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si10.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=b5fc379955006cd5e41053b8bbf2e721">class="imgLazyJSB inlineImage" height="17" width="113" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0166218X16302189-si10.gif">class="mathContainer hidden">class="mathCode">, the complexity of counting class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si11.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=1750eeba9862b1fce9a11669839235ed" title="Click to view the MathML source">Mclass="mathContainer hidden">class="mathCode">-partitions is the same as the related problem of counting list class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0166218X16302189&_mathId=si11.gif&_user=111111111&_pii=S0166218X16302189&_rdoc=1&_issn=0166218X&md5=1750eeba9862b1fce9a11669839235ed" title="Click to view the MathML source">Mclass="mathContainer hidden">class="mathCode">-partitions.